The document discusses amino acid metabolism and the urea cycle. It begins by explaining that amino acids can provide metabolic energy through oxidative degradation. It then describes the urea cycle, a cyclic pathway that occurs in the liver to convert ammonia into urea for excretion. The cycle involves 4 steps that take place between the mitochondria and cytosol of liver cells: 1) carbamoyl phosphate is formed in mitochondria and reacts to form citrulline, 2) citrulline reacts with aspartate in the cytosol to form argininosuccinate, 3) argininosuccinate splits into arginine and fumarate, 4) arginase cleaves arginine into ornithine
The document summarizes the catabolism of amino acids. It discusses how excess amino acids are degraded by removing their amino groups via transamination and oxidative deamination, forming ammonia and keto acids. Most ammonia is incorporated into urea in the liver via the urea cycle for excretion. The amino acid pool is supplied from endogenous protein breakdown, dietary protein, and nonessential amino acid synthesis. It is depleted through protein synthesis, incorporation into other molecules, and oxidation. Protein turnover constantly synthesizes and degrades proteins. The steps of amino acid catabolism include transamination, oxidative deamination, ammonia transport to the liver, and the urea cycle.
The document discusses the urea cycle, which involves a cyclic set of chemical reactions that occur in the liver to convert ammonia into urea for excretion. It details the 5 enzyme-catalyzed reactions, participating amino acids and cofactors. One molecule of urea requires 3 ATP and utilizes ammonia, bicarbonate, and aspartate. The cycle is regulated by N-acetyl glutamate and compartmentalized between mitochondria and cytosol. Disorders cause hyperammonemia due to deficient enzymes, with earlier blocks causing more severe symptoms like vomiting and lethargy.
Protein metabolism denotes the various biochemical processes responsible for the synthesis of proteins and amino acids (anabolism), and the breakdown of proteins by catabolism. ... In humans, non-essential amino acids are synthesized from intermediates in major metabolic pathways such as the Citric Acid Cycle.
The urea cycle converts toxic ammonia produced during protein catabolism into urea for excretion. It occurs in the liver and involves 5 steps: (1) carbamoyl phosphate synthesis using NH3 and ATP, (2) citrulline formation from carbamoyl phosphate and ornithine, (3) argininosuccinate synthesis from citrulline and aspartate using ATP, (4) arginine formation from argininosuccinate, and (5) urea and ornithine formation from arginine using arginase. The cycle is regulated by N-acetylglutamate and produces fumarate, which links it to the TCA cycle and gluconeogenesis. It consumes
Proteins are essential macromolecules that make up the structure and carry out functions in the body. They are composed of amino acids, which can be synthesized by the body or obtained through diet. Amino acids undergo catabolism through four main stages: transamination, oxidative deamination, ammonia transport, and the urea cycle. The urea cycle is crucial for detoxifying ammonia produced from amino acid catabolism and involves six enzymes that convert ammonia to urea in the liver for excretion. Defects in the urea cycle can cause hyperammonemia, which can be toxic to the brain if not addressed.
The document summarizes amino acid metabolism. Key points include:
1. Proteins are broken down into amino acids which can be used for energy, regulation of metabolism, or synthesis of other compounds.
2. Amino acids are absorbed from the small intestine and transported via blood plasma to tissues where they undergo reactions like transamination or direct deamination to produce metabolic intermediates or urea.
3. The urea cycle operates in the liver to detoxify ammonia produced from amino acid breakdown into urea for excretion.
The document summarizes the catabolism of amino acids. It discusses how excess amino acids are degraded by removing their amino groups via transamination and oxidative deamination, forming ammonia and keto acids. Most ammonia is incorporated into urea in the liver via the urea cycle for excretion. The amino acid pool is supplied from endogenous protein breakdown, dietary protein, and nonessential amino acid synthesis. It is depleted through protein synthesis, incorporation into other molecules, and oxidation. Protein turnover constantly synthesizes and degrades proteins. The steps of amino acid catabolism include transamination, oxidative deamination, ammonia transport to the liver, and the urea cycle.
The document discusses the urea cycle, which involves a cyclic set of chemical reactions that occur in the liver to convert ammonia into urea for excretion. It details the 5 enzyme-catalyzed reactions, participating amino acids and cofactors. One molecule of urea requires 3 ATP and utilizes ammonia, bicarbonate, and aspartate. The cycle is regulated by N-acetyl glutamate and compartmentalized between mitochondria and cytosol. Disorders cause hyperammonemia due to deficient enzymes, with earlier blocks causing more severe symptoms like vomiting and lethargy.
Protein metabolism denotes the various biochemical processes responsible for the synthesis of proteins and amino acids (anabolism), and the breakdown of proteins by catabolism. ... In humans, non-essential amino acids are synthesized from intermediates in major metabolic pathways such as the Citric Acid Cycle.
The urea cycle converts toxic ammonia produced during protein catabolism into urea for excretion. It occurs in the liver and involves 5 steps: (1) carbamoyl phosphate synthesis using NH3 and ATP, (2) citrulline formation from carbamoyl phosphate and ornithine, (3) argininosuccinate synthesis from citrulline and aspartate using ATP, (4) arginine formation from argininosuccinate, and (5) urea and ornithine formation from arginine using arginase. The cycle is regulated by N-acetylglutamate and produces fumarate, which links it to the TCA cycle and gluconeogenesis. It consumes
Proteins are essential macromolecules that make up the structure and carry out functions in the body. They are composed of amino acids, which can be synthesized by the body or obtained through diet. Amino acids undergo catabolism through four main stages: transamination, oxidative deamination, ammonia transport, and the urea cycle. The urea cycle is crucial for detoxifying ammonia produced from amino acid catabolism and involves six enzymes that convert ammonia to urea in the liver for excretion. Defects in the urea cycle can cause hyperammonemia, which can be toxic to the brain if not addressed.
The document summarizes amino acid metabolism. Key points include:
1. Proteins are broken down into amino acids which can be used for energy, regulation of metabolism, or synthesis of other compounds.
2. Amino acids are absorbed from the small intestine and transported via blood plasma to tissues where they undergo reactions like transamination or direct deamination to produce metabolic intermediates or urea.
3. The urea cycle operates in the liver to detoxify ammonia produced from amino acid breakdown into urea for excretion.
The urea cycle is the metabolic pathway that transforms nitrogen to urea for excretion from the body. Liver cells play a critical role in disposing of nitrogenous waste by forming urea hrough the action of the urea cycle.
Nitrogenous excretory products are then removed from the body through in the urine.
The urea excreted each day by a healthy adult (about 30 g) accounts for about 90% of the nitrogenous excretory products.
The cycle occurs mainly in the liver.
The urea cycle is a metabolic pathway that occurs in the liver to convert excess nitrogen from amino acid catabolism into urea for excretion. It involves five enzymes and five steps to synthesize urea from ammonia and carbon dioxide. Defects in the urea cycle can cause hyperammonemia, where high ammonia levels impair the citric acid cycle and ATP production in the brain.
The document discusses amino acid catabolism and the relationships between organs in metabolizing and transporting amino acids and nitrogen. The intestine absorbs amino acids from food and releases byproducts like ammonium and alanine. The liver synthesizes proteins, breaks down amino acids, and performs gluconeogenesis and urea synthesis. Skeletal muscle breaks down branched chain amino acids and transports amino groups as alanine and glutamine to other organs. One clinical case describes a infant with high blood ammonium levels due to a genetic deficiency in ornithine transcarbamoylase, an enzyme in the urea cycle. Treatment with essential amino acids and sodium benzoate helped reduce ammonium levels.
1) Proteins are digested in the stomach by pepsin and in the small intestine by trypsin, chymotrypsin, and other pancreatic enzymes into dipeptides and tripeptides.
2) Amino acids are absorbed in the small intestine through carrier-mediated transport systems and used to build new proteins or for energy production.
3) Excess amino acids are broken down through transamination and the urea cycle to form urea, which is excreted in urine to remove waste nitrogen from the body. Disorders of the urea cycle can cause toxic buildup of ammonia in the blood.
Amino acids act as building blocks for proteins and other biomolecules. During catabolism, the amino group is removed from amino acids and transferred to α-ketoglutarate to form glutamate, leaving behind carbon skeletons that can enter the TCA cycle. Amino acids are synthesized through a variety of pathways that involve transamination reactions and the transfer of one-carbon units. Certain amino acids cannot be synthesized de novo by the human body and must be obtained through the diet.
This PPT is on Amino acid metabolism. And the topics covered under this ppt are Transamination, deamination
Book referred: https://www.amazon.in/Biochemistry-2019-Satyanarayana-Satyanarayana-Author/dp/B07WGHCTKZ/ref=sr_1_1?dchild=1&qid=1591608419&refinements=p_27%3AU+Satyanarayana&s=books&sr=1-1
1) Amino acids from dietary proteins and cellular protein turnover enter an amino acid pool in the body. Glutamate and glutamine make up about 50% of this pool.
2) Amino acids are used to generate energy, synthesize proteins, and produce other nitrogenous compounds. They undergo transamination and deamination, with the amino groups being converted to ammonia.
3) Ammonia is disposed of through the urea cycle in mammals, where it is combined with carbon dioxide to form urea, which is excreted in urine. Disorders of the urea cycle can cause hyperammonemia and neurological issues.
Amino acids can be used for energy production or as building blocks for proteins. Excess amino acids are broken down and their nitrogen is converted to urea via transamination, deamination, and the urea cycle to be excreted. Their carbon skeletons can be used for energy, gluconeogenesis, or triglyceride synthesis. Ten non-essential amino acids can be synthesized from intermediates in glycolysis and the citric acid cycle through various pathways.
This document discusses protein metabolism, including oxidative deamination, transamination, decarboxylation, and transmethylation. It also discusses the pentose phosphate pathway (PPP), also known as the hexose monophosphate (HMP) shunt, Warburg-Dickens pathway, and other names. The PPP provides an alternative pathway to glycolysis for carbohydrate breakdown and generates NADPH for biosynthetic processes. It is important for producing pentose sugars, aromatic compounds, nucleotides, and reducing power for biosynthesis.
The document discusses the urea cycle, which is the process by which excess nitrogen from amino acid catabolism is converted to urea for excretion. It describes the six amino acids and five enzymes involved in the cyclic urea formation reactions, which take place in the liver. Defects in the urea cycle enzymes can cause hyperammonemia due to the buildup of toxic ammonia, often presenting in newborns but sometimes not until later in life. Laboratory tests of blood ammonia levels, amino acid levels, and genetic testing can help diagnose specific urea cycle disorders.
All tissues have some capability for synthesis of the non-essential amino acids, amino acid remodeling, and conversion of non-amino acid carbon skeletons into amino acids and other derivatives that contain nitrogen. However, the liver is the major site of nitrogen metabolism in the body.
Amino acid metabolism and uea cycle convertedGAnchal
Proteins are broken down into amino acids which then undergo various metabolic fates including transamination, deamination, and decarboxylation. Transamination involves the transfer of amino groups between amino acids and keto acids using pyridoxal phosphate as a cofactor. Deamination can be either oxidative, releasing ammonia with oxidation, or non-oxidative, releasing ammonia without oxidation. Decarboxylation removes a carboxyl group from an amino acid to form an amine. To detoxify ammonia produced from amino acid catabolism, the urea cycle operates in the liver to convert ammonia into urea for excretion in urine.
Protein metabolism involves the breakdown of proteins into amino acids and their use and degradation throughout the body. Amino acids from food sources are broken down through digestion and absorbed. They are used for protein synthesis, forming hormones and other compounds, and undergo constant breakdown and renewal to replenish amino acid reserves. Excess amino acids have their nitrogen removed through transamination or oxidative deamination, producing ammonia. The liver plays a key role in nitrogen excretion by converting toxic ammonia into less toxic urea via the urea cycle, which is then excreted in urine.
The document discusses nitrogen metabolism and the digestion and absorption of proteins. It notes that amino acids from dietary proteins and broken down body proteins enter an amino acid pool. They can then be used to synthesize new body proteins or undergo catabolism where the nitrogen is removed and converted to urea or ammonia for excretion. The document describes the multi-step process of protein digestion by enzymes in the stomach, pancreas and intestines breaking proteins down into amino acids that are then absorbed into the bloodstream.
The document discusses amino acid metabolism. It begins by outlining the major pathways of amino acid metabolism, including transamination, deamination, and decarboxylation. These pathways allow amino acids to be used for protein synthesis, energy production, and the formation of other nitrogenous compounds. The urea cycle is also summarized, which involves several steps to produce urea from ammonia in the liver. Finally, some specific amino acids like glycine are discussed in more detail regarding their catabolism. In general, the carbon skeletons of amino acids enter central metabolic pathways while the amino groups are removed as ammonia and ultimately excreted as urea.
Biochemistry ii protein (metabolism of amino acids) (new edition)abdulhussien aljebory
This document discusses the metabolism of amino acids. It begins with an introduction and overview of amino acid classification, definitions of terms like nitrogen balance and biological value, and the digestion and absorption of proteins. It then covers the metabolic fates of amino acids, including removal of ammonia via deamination, transamination, and transdeamination. The carbon skeletons of amino acids can be used for biosynthesis, the synthesis of non-protein nitrogen compounds, or energy production. Ammonia is further metabolized. Overall, the document provides a comprehensive overview of the key processes in amino acid metabolism.
Amino acids are degraded through transamination and oxidation reactions. During degradation, amino acids lose their amino group to form alpha-keto acids. The carbon skeletons are then further oxidized, producing metabolites like pyruvic acid, acetoacetic acid, succinyl-CoA, oxaloacetic acid, or alpha-ketoglutaric acid. These intermediates can be converted to glucose, ketone bodies, or fed into the citric acid cycle. In ureotelic organisms, ammonia produced from amino acid degradation is incorporated into the urea cycle in the liver and converted to urea for excretion. Key enzymes and cofactors involved include transaminases, glutamate dehydrogenase
The document discusses amino acid metabolism and the urea cycle. It provides details on:
1. Amino acids undergo oxidative degradation to generate energy in animals. Excess amino acids from dietary protein are broken down and the nitrogen is removed as ammonia in the liver.
2. The liver converts ammonia into less toxic urea through the urea cycle. This involves transferring amino groups to glutamate and transporting them to the liver via glutamine or alanine.
3. The urea cycle consists of converting ammonia into carbamoyl phosphate then citrulline, argininosuccinate, arginine, and finally urea which is excreted. This removes nitrogen from amino acid
1) Nitrogen enters the body through dietary protein and is metabolized through amino acids. Amino acids are broken down and the nitrogen is removed as ammonia, which is converted to urea to be excreted.
2) The amino acid pool and protein turnover are key concepts in nitrogen metabolism. Amino acids from protein breakdown replenish the amino acid pool, which is also used for protein synthesis and other processes.
3) Dietary proteins are digested by enzymes in the stomach and pancreas into dipeptides and tripeptides, then fully into amino acids by intestinal enzymes for absorption.
The urea cycle is the metabolic pathway that transforms nitrogen to urea for excretion from the body. Liver cells play a critical role in disposing of nitrogenous waste by forming urea hrough the action of the urea cycle.
Nitrogenous excretory products are then removed from the body through in the urine.
The urea excreted each day by a healthy adult (about 30 g) accounts for about 90% of the nitrogenous excretory products.
The cycle occurs mainly in the liver.
The urea cycle is a metabolic pathway that occurs in the liver to convert excess nitrogen from amino acid catabolism into urea for excretion. It involves five enzymes and five steps to synthesize urea from ammonia and carbon dioxide. Defects in the urea cycle can cause hyperammonemia, where high ammonia levels impair the citric acid cycle and ATP production in the brain.
The document discusses amino acid catabolism and the relationships between organs in metabolizing and transporting amino acids and nitrogen. The intestine absorbs amino acids from food and releases byproducts like ammonium and alanine. The liver synthesizes proteins, breaks down amino acids, and performs gluconeogenesis and urea synthesis. Skeletal muscle breaks down branched chain amino acids and transports amino groups as alanine and glutamine to other organs. One clinical case describes a infant with high blood ammonium levels due to a genetic deficiency in ornithine transcarbamoylase, an enzyme in the urea cycle. Treatment with essential amino acids and sodium benzoate helped reduce ammonium levels.
1) Proteins are digested in the stomach by pepsin and in the small intestine by trypsin, chymotrypsin, and other pancreatic enzymes into dipeptides and tripeptides.
2) Amino acids are absorbed in the small intestine through carrier-mediated transport systems and used to build new proteins or for energy production.
3) Excess amino acids are broken down through transamination and the urea cycle to form urea, which is excreted in urine to remove waste nitrogen from the body. Disorders of the urea cycle can cause toxic buildup of ammonia in the blood.
Amino acids act as building blocks for proteins and other biomolecules. During catabolism, the amino group is removed from amino acids and transferred to α-ketoglutarate to form glutamate, leaving behind carbon skeletons that can enter the TCA cycle. Amino acids are synthesized through a variety of pathways that involve transamination reactions and the transfer of one-carbon units. Certain amino acids cannot be synthesized de novo by the human body and must be obtained through the diet.
This PPT is on Amino acid metabolism. And the topics covered under this ppt are Transamination, deamination
Book referred: https://www.amazon.in/Biochemistry-2019-Satyanarayana-Satyanarayana-Author/dp/B07WGHCTKZ/ref=sr_1_1?dchild=1&qid=1591608419&refinements=p_27%3AU+Satyanarayana&s=books&sr=1-1
1) Amino acids from dietary proteins and cellular protein turnover enter an amino acid pool in the body. Glutamate and glutamine make up about 50% of this pool.
2) Amino acids are used to generate energy, synthesize proteins, and produce other nitrogenous compounds. They undergo transamination and deamination, with the amino groups being converted to ammonia.
3) Ammonia is disposed of through the urea cycle in mammals, where it is combined with carbon dioxide to form urea, which is excreted in urine. Disorders of the urea cycle can cause hyperammonemia and neurological issues.
Amino acids can be used for energy production or as building blocks for proteins. Excess amino acids are broken down and their nitrogen is converted to urea via transamination, deamination, and the urea cycle to be excreted. Their carbon skeletons can be used for energy, gluconeogenesis, or triglyceride synthesis. Ten non-essential amino acids can be synthesized from intermediates in glycolysis and the citric acid cycle through various pathways.
This document discusses protein metabolism, including oxidative deamination, transamination, decarboxylation, and transmethylation. It also discusses the pentose phosphate pathway (PPP), also known as the hexose monophosphate (HMP) shunt, Warburg-Dickens pathway, and other names. The PPP provides an alternative pathway to glycolysis for carbohydrate breakdown and generates NADPH for biosynthetic processes. It is important for producing pentose sugars, aromatic compounds, nucleotides, and reducing power for biosynthesis.
The document discusses the urea cycle, which is the process by which excess nitrogen from amino acid catabolism is converted to urea for excretion. It describes the six amino acids and five enzymes involved in the cyclic urea formation reactions, which take place in the liver. Defects in the urea cycle enzymes can cause hyperammonemia due to the buildup of toxic ammonia, often presenting in newborns but sometimes not until later in life. Laboratory tests of blood ammonia levels, amino acid levels, and genetic testing can help diagnose specific urea cycle disorders.
All tissues have some capability for synthesis of the non-essential amino acids, amino acid remodeling, and conversion of non-amino acid carbon skeletons into amino acids and other derivatives that contain nitrogen. However, the liver is the major site of nitrogen metabolism in the body.
Amino acid metabolism and uea cycle convertedGAnchal
Proteins are broken down into amino acids which then undergo various metabolic fates including transamination, deamination, and decarboxylation. Transamination involves the transfer of amino groups between amino acids and keto acids using pyridoxal phosphate as a cofactor. Deamination can be either oxidative, releasing ammonia with oxidation, or non-oxidative, releasing ammonia without oxidation. Decarboxylation removes a carboxyl group from an amino acid to form an amine. To detoxify ammonia produced from amino acid catabolism, the urea cycle operates in the liver to convert ammonia into urea for excretion in urine.
Protein metabolism involves the breakdown of proteins into amino acids and their use and degradation throughout the body. Amino acids from food sources are broken down through digestion and absorbed. They are used for protein synthesis, forming hormones and other compounds, and undergo constant breakdown and renewal to replenish amino acid reserves. Excess amino acids have their nitrogen removed through transamination or oxidative deamination, producing ammonia. The liver plays a key role in nitrogen excretion by converting toxic ammonia into less toxic urea via the urea cycle, which is then excreted in urine.
The document discusses nitrogen metabolism and the digestion and absorption of proteins. It notes that amino acids from dietary proteins and broken down body proteins enter an amino acid pool. They can then be used to synthesize new body proteins or undergo catabolism where the nitrogen is removed and converted to urea or ammonia for excretion. The document describes the multi-step process of protein digestion by enzymes in the stomach, pancreas and intestines breaking proteins down into amino acids that are then absorbed into the bloodstream.
The document discusses amino acid metabolism. It begins by outlining the major pathways of amino acid metabolism, including transamination, deamination, and decarboxylation. These pathways allow amino acids to be used for protein synthesis, energy production, and the formation of other nitrogenous compounds. The urea cycle is also summarized, which involves several steps to produce urea from ammonia in the liver. Finally, some specific amino acids like glycine are discussed in more detail regarding their catabolism. In general, the carbon skeletons of amino acids enter central metabolic pathways while the amino groups are removed as ammonia and ultimately excreted as urea.
Biochemistry ii protein (metabolism of amino acids) (new edition)abdulhussien aljebory
This document discusses the metabolism of amino acids. It begins with an introduction and overview of amino acid classification, definitions of terms like nitrogen balance and biological value, and the digestion and absorption of proteins. It then covers the metabolic fates of amino acids, including removal of ammonia via deamination, transamination, and transdeamination. The carbon skeletons of amino acids can be used for biosynthesis, the synthesis of non-protein nitrogen compounds, or energy production. Ammonia is further metabolized. Overall, the document provides a comprehensive overview of the key processes in amino acid metabolism.
Amino acids are degraded through transamination and oxidation reactions. During degradation, amino acids lose their amino group to form alpha-keto acids. The carbon skeletons are then further oxidized, producing metabolites like pyruvic acid, acetoacetic acid, succinyl-CoA, oxaloacetic acid, or alpha-ketoglutaric acid. These intermediates can be converted to glucose, ketone bodies, or fed into the citric acid cycle. In ureotelic organisms, ammonia produced from amino acid degradation is incorporated into the urea cycle in the liver and converted to urea for excretion. Key enzymes and cofactors involved include transaminases, glutamate dehydrogenase
The document discusses amino acid metabolism and the urea cycle. It provides details on:
1. Amino acids undergo oxidative degradation to generate energy in animals. Excess amino acids from dietary protein are broken down and the nitrogen is removed as ammonia in the liver.
2. The liver converts ammonia into less toxic urea through the urea cycle. This involves transferring amino groups to glutamate and transporting them to the liver via glutamine or alanine.
3. The urea cycle consists of converting ammonia into carbamoyl phosphate then citrulline, argininosuccinate, arginine, and finally urea which is excreted. This removes nitrogen from amino acid
1) Nitrogen enters the body through dietary protein and is metabolized through amino acids. Amino acids are broken down and the nitrogen is removed as ammonia, which is converted to urea to be excreted.
2) The amino acid pool and protein turnover are key concepts in nitrogen metabolism. Amino acids from protein breakdown replenish the amino acid pool, which is also used for protein synthesis and other processes.
3) Dietary proteins are digested by enzymes in the stomach and pancreas into dipeptides and tripeptides, then fully into amino acids by intestinal enzymes for absorption.
Amino acids from dietary proteins and endogenous protein turnover can be used as an energy source in animals. Carnivores can obtain about 90% of their energy needs from amino acid oxidation after eating. Amino acids are broken down into common intermediate metabolites through transamination and deamination reactions. Excess amino groups are removed as ammonia, which is converted to less toxic urea primarily in the liver and excreted by the kidneys.
Amino acid catabolism and urea cycle.pptxHashimBashir1
Citric acid is a versatile organic acid found in many fruits, especially citrus fruits like lemons, oranges, limes, and grapefruits. Its chemical formula is C6H8O7, and it's classified as a weak acid. Citric acid has a wide range of applications, from food and beverage production to household cleaning and skincare. In this comprehensive description, I'll delve into its properties, uses, production methods, health effects, and environmental impact.
*1. Properties of Citric Acid:*
Citric acid appears as a white crystalline powder or granules. It's odorless and has a tart, sour taste. It's highly soluble in water, making it easy to incorporate into various products. Citric acid is stable at room temperature but decomposes at higher temperatures, losing its acidic properties. It's a chelating agent, meaning it can bind to metal ions, making it useful in certain industrial processes and household cleaners.
*2. Sources of Citric Acid:*
While citric acid occurs naturally in citrus fruits, it's also produced commercially through microbial fermentation, primarily using strains of the fungus Aspergillus niger. This method allows for large-scale production of citric acid to meet the demand in various industries. Additionally, it can be synthesized chemically, although this method is less common due to higher production costs and environmental concerns.
*3. Uses of Citric Acid:*
*- Food and Beverage Industry:* Citric acid is widely used as a flavoring agent, acidity regulator, and preservative in the food and beverage industry. It enhances the flavor of many products and provides a tart taste in sodas, candies, jams, and preserves. It also acts as a preservative, extending the shelf life of packaged foods and preventing discoloration in fruits and vegetables.
*- Pharmaceutical Industry:* Citric acid is used in pharmaceuticals as a pH regulator, excipient in tablets and capsules, and as a flavoring agent in syrups and liquid medications.
*- Cleaning Products:* Due to its chelating properties, citric acid is used in household cleaning products such as descalers, bathroom cleaners, and dishwashing detergents. It effectively removes mineral deposits and stains without the need for harsh chemicals.
*- Cosmetics and Personal Care:* Citric acid is found in skincare products like exfoliating scrubs, facial peels, and anti-aging creams. It helps to promote skin renewal by gently removing dead skin cells and promoting collagen production.
*- Industrial Applications:* Citric acid is used in various industrial processes, including water softening, metal cleaning, and the production of detergents and surfactants.
*4. Production Methods:*
*- Microbial Fermentation:* This is the most common method for commercial production of citric acid. It involves fermenting glucose or sucrose-containing substrates with strains of Aspergillus niger in large-scale bioreactors. The fungus produces citric acid as a byproduct of its metabolism, which is then extracted and purified.
*- C
1) Proteins in the diet are broken down into smaller peptides and individual amino acids through digestion by proteolytic enzymes in the stomach, pancreas, and intestines.
2) In the liver, amino acids are broken down through transamination and transdeamination reactions to produce ammonia, which is highly toxic.
3) Ammonia is detoxified in the liver through the urea cycle into urea, which is excreted in the urine. Deficiencies in urea cycle enzymes can cause a toxic buildup of ammonia in the blood.
This document summarizes protein digestion and metabolism. It describes how proteins are broken down into peptides and amino acids via proteolytic enzymes in the stomach, pancreas, and intestines. The amino acids are then absorbed. Amino groups from amino acid catabolism form ammonia, which is detoxified to urea in the urea cycle in the liver to prevent toxicity. Disorders of this cycle can cause hyperammonemia. Blood urea levels indicate renal function, while urea is the main organic component excreted in urine.
This document discusses protein metabolism, including essential and non-essential amino acids. Essential amino acids cannot be synthesized by the human body and must be obtained through diet. Non-essential amino acids can be synthesized from other amino acids or compounds. The document also outlines the processes of protein digestion, amino acid catabolism through transamination and the urea cycle, and analytical techniques for purifying and characterizing proteins like polyacrylamide gel electrophoresis and Edman degradation.
This document summarizes key aspects of protein metabolism from several sections of Chapter 26. It discusses protein digestion and absorption in the stomach and small intestine. Amino acids enter the amino acid pool and are used for protein synthesis, synthesis of other nitrogen-containing compounds, and energy production. The removal of amino groups via transamination and oxidative deamination is described. The urea cycle, which converts toxic ammonia into urea for excretion, is summarized. The document outlines the different fates of the carbon skeletons of amino acids and their roles in gluconeogenesis and ketogenesis. Hemoglobin catabolism and the production of bile pigments is briefly explained. Finally, the interrelationships between carbohydrate, lipid, and protein
Formation and fate of Ammonia
Transdeamination, oxidative and non oxidative deamination, Ammonia transport, Ammonia intoxication, Ammonia detoxification
ABSALON_BioChem_Protein and Amino Acid Metabolism.pptxZeref77
Proteins are complex biological molecules composed of amino acids. The body breaks down ingested proteins into individual amino acids, which can then be used to synthesize new proteins or metabolized for energy. Amino acid metabolism involves pathways that classify amino acids as either glucogenic, producing glucose, or ketogenic, producing ketone bodies. Enzymes play an important role in catalyzing the synthesis and breakdown of amino acids, and disorders can occur if these enzymatic pathways are disrupted.
This document discusses amino acid metabolism and the urea cycle. It begins with an introduction to amino acids, their roles in the body, and how they are broken down into individual amino acids. It then describes the processes of transamination and deamination, by which amino groups are transferred between amino acids and their carbon skeletons are converted to keto acids. One key reaction is glutamate serving as a collection point for amino groups. The urea cycle is then introduced as the process by which ammonia produced from amino acid breakdown is detoxified into urea for excretion. The urea cycle involves 5 enzymes and 4 ATP and occurs primarily in the liver.
Metabolism of amino acids (general metabolism)Ashok Katta
Metabolism of amino acids (general metabolism).
Part - I of amino acid metabolism.
This presentation covers Transamination, deamination, formation and Transport of Ammoniaand etc.
This document summarizes nitrogen metabolism and amino acid catabolism. It discusses how nitrogen is essential for organisms and how most nitrogen conversions are catalyzed by bacterial and archaeal enzymes. It describes the different types of amino acids and their importance as building blocks of proteins and for synthesizing other nitrogenous molecules. The document outlines the metabolic fates of amino acids including protein synthesis, degradation through deamination or transamination, and the pathways of ketogenic and glucogenic amino acids. It also summarizes amino acid digestion, absorption, transport, and degradation through the urea cycle which occurs in the liver to excrete nitrogen waste from amino acid catabolism.
1. Fatty acids from dietary triglycerides and adipose tissue are broken down through beta-oxidation in the mitochondria to produce acetyl-CoA, which feeds into the Krebs cycle.
2. Triglycerides must be emulsified to be digested and transported via chylomicrons in the bloodstream for use or storage.
3. Amino acids are broken down through transamination and the urea cycle to remove nitrogenous waste, while their carbon skeletons can be used for energy or biosynthesis as either glucogenic or ketogenic intermediates.
The document discusses amino acid metabolism. It begins by defining amino acids as derivatives of carboxylic acids with an amino group substitution. Amino acids are essential for building proteins and participate in many metabolic reactions. They are classified by the properties of their side chains. Protein digestion involves proteases in the stomach, pancreas, and small intestine that hydrolyze proteins into amino acids. Amino acids are absorbed into the blood and transported to tissues. Within cells, amino groups are transferred between amino acids and ketoacids in transamination reactions or removed as ammonia by deamination. The liver converts ammonia into less toxic urea via the urea cycle to prevent intoxication. Defects in the urea cycle can
Amino acids function as monomers of polypeptides.
Energy metabolites.
Precursors for nitrogen-containing compounds (heme, glutathione, nucleotides, coenzymes)
Amino acids are classified into 2 groups: essential and nonessential
Mammals can synthesize nonessential amino acids from metabolic precursors.
Essential amino acids must be taken in from diet.
Excess dietary amino acids are converted to common metabolic intermediates: pyruvate, OAA, acetyl-CoA, and -ketoglutarate.
Protein digestion begins in the stomach where dietary protein stimulates the release of gastrin. Gastrin promotes the secretion of pepsinogen and hydrochloric acid (HCl) from the stomach. HCl performs several functions including killing bacteria, denaturing proteins, and activating pepsinogen. Pepsinogen is converted to the active enzyme pepsin, which hydrolyzes around 10% of dietary peptide bonds in the stomach. Further digestion occurs in the small intestine where pancreatic enzymes complete the breakdown of proteins into amino acids. The liberated amino acids are then absorbed into the bloodstream.
1) Amino acids are used primarily for protein synthesis rather than as an energy source. They can be used for energy only when carbohydrate and lipid availability is low.
2) Amino acids enter the body through digestion of proteins and are used for protein synthesis, specialized non-protein product synthesis, and as an energy source.
3) Excess amino acids are deaminated, producing ammonia which is converted to urea to prevent toxicity. Urea is synthesized in the liver through the urea cycle and excreted by the kidneys.
Similar to Amino acid meatbolism and urea cycle(1) (20)
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BIOLOGY NATIONAL EXAMINATION COUNCIL (NECO) 2024 PRACTICAL MANUAL.pptx
Amino acid meatbolism and urea cycle(1)
1. Amino acid Metabolism and Urea cycle
Asad Ullah Khan
Student of BS_Anesthesia
REHMAN MEDICAL INSTITUTE PESHAWAR
Wednesday, July 26, 2017 1
2. Amino acid metabolism
• Amino acids are the final class of biomolecules that, through their
oxidative degradation, make a significant contribution to the generation of
metabolic energy.
• The fraction of metabolic energy obtained from amino acids, whether they
are derived from dietary protein or from tissue protein, varies greatly with
the type of organism and with metabolic conditions.
• Carnivores can obtain (immediately following a meal) up to 90% of their
energy requirements from amino acid oxidation, whereas herbivores may
fill only a small fraction of their energy needs by this route.
Wednesday, July 26, 2017 2
3. Amino acid metabolism
• Most microorganisms can scavenge amino acids from their
environment and use them as fuel when required by metabolic
conditions.
• Plants, however, rarely if ever oxidize amino acids to provide energy;
the carbohydrate produced from CO2 and H2O in photosynthesis is
generally their sole energy source.
Wednesday, July 26, 2017 3
4. Amino acid metabolism
• In animals, amino acids undergo oxidative degradation in three
different metabolic circumstances:
1. During the normal synthesis and degradation of cellular proteins
some amino acids that are released from protein breakdown and
are not needed for new protein synthesis undergo oxidative
degradation.
2. During intake of protein rich diet and the ingested amino acids
exceed the body’s needs for protein synthesis, the surplus is
catabolized; amino acids cannot be stored.
3. During starvation or in uncontrolled diabetes mellitus, when
carbohydrates are either unavailable or not properly utilized,
cellular proteins are used as fuel.
Wednesday, July 26, 2017 4
5. Overview of amino acid metabolism
• Proteins constantly undergo
turnover.
• Amino acids are also used to
synthesize some non-protein
metabolites.
• No protein stores, so essential
amino acids must come from
diet.
Wednesday, July 26, 2017 5
6. Amino acid metabolism
• Pathways leading to amino acid degradation are quite alike in most
organisms.
• As is the case for sugar and fatty acid catabolic pathways, the
processes of amino acid degradation converge on the central
catabolic pathways for carbon metabolism.
• However, one major factor distinguishes amino acid degradation from
the catabolic processes described till now, i.e., every amino acid
contains an amino group.
• As such every degradative pathway passes through a key step in
which α-amino group is separated from the carbon skeleton and
shunted into the specialized pathways for amino group metabolism
Wednesday, July 26, 2017 6
7. Amino acid metabolism
• The α-amino group of the amino acids is removed and the resulting carbon
skeleton is converted into a major metabolic intermediate.
• Most of the amino groups of surplus amino acids are converted into urea
whereas their carbon skeletons are transferred to acetyl-CoA, acetoacetyl-
CoA, pyruvate, or one of the intermediates of the citric acid cycle.
• It follows that amino acids can form glucose, fatty acids and ketone bodies.
• The major site of amino acid degradation in mammals is the liver.
Wednesday, July 26, 2017 7
8. Overview of amino acid catabolism in mammals
Two choices
1.Reuse
2.Urea cycle
Fumarate
Oxaloacetate
Wednesday, July 26, 2017 8
9. Metabolic fates of amino groups
• Transfer of Amino Groups to Glutamate:
• The α-amino groups of the 20 L-amino acids, commonly found in
proteins, are removed during the oxidative degradation of the amino
acids.
• If not reused for the synthesis of new amino acids, these amino
groups are channeled into a single excretory product.
• Many aquatic organisms simply release ammonia as NH4+ into the
surrounding medium.
• Most terrestrial vertebrates first convert ammonia into either urea
(e.g., humans, other mammals and adult amphibians) or uric acid
(e.g., reptiles, birds).
Wednesday, July 26, 2017 9
10. Metabolic fates of amino groups
• The first step in the catabolism of most of the L-amino acids is the removal
of the α-amino group (i.e., transamination) by a group of enzymes called
aminotransferases (= transaminases).
• In these reactions, the α-amino group is transferred to the α-carbon atom
of α-ketoglutarate, leaving behind the corresponding α-keto acid analogue
of the amino acid.
• The effect of transamination reactions is to collect the amino groups from
many different amino acids in the form of only one, namely L-glutamate.
• Cells contain several different aminotransferases, many of which are
specific for α ketoglutarate as the amino group acceptor.
• The amino-transferases differ in their specificity for the other substrate
(i.e., the L-amino acid that donates the amino group) and are named for
the amino group donor.
Wednesday, July 26, 2017 10
12. Metabolic Fates of Amino Groups
• Nitrogen, N2, is abundant in the atmosphere but is too inert for use
in most biochemical processes.
• Because only a few microorganisms can convert N2 to biologically
useful forms such as NH3, amino groups are carefully conserved in
biological systems.
Wednesday, July 26, 2017 12
13. Nitrogen balance
Tissue proteins
Dietary
proteins
Amino acid
pool
Excretion
as urea and
NH4
+
Purines, heme, etc.
Energy
The amount of nitrogen ingested is balanced by the excretion of an
equivalent amount of nitrogen. About 80% of excreted nitrogen is in the
form of urea.
Wednesday, July 26, 2017 13
14. Metabolic Fates of Amino Groups
• Amino acids derived from dietary protein are the source of most amino
groups.
• Most amino acids are metabolized in the liver.
• Some of the ammonia generated in this process is recycled and used in a
variety of biosynthetic pathways; the excess is either excreted directly or
converted to urea or uric acid for excretion, depending on the organism.
• Excess ammonia generated in other (extrahepatic) tissues travels to the
liver for conversion to the excretory form.
Wednesday, July 26, 2017 14
15. Excretory forms of nitrogen
a) Excess NH4
+ is excreted as ammonia (microbes, aquatic
vertebrates or larvae of amphibia),
b) Urea (many terrestrial vertebrates)
c) or uric acid (birds and terrestrial reptiles)
Wednesday, July 26, 2017 15
16. Metabolic Fates of Amino Groups
• Four amino acids play central roles in nitrogen metabolism.
• glutamate, glutamine, alanine, and aspartate.
• The special place of these four amino acids is due to that these
particular amino acids are the ones most easily converted into citric
acid cycle intermediates: glutamate and glutamine to -ketoglutarate,
alanine to pyruvate, and aspartate to oxaloacetate.
• Glutamate and glutamine are especially important, acting as a kind
of general collection point for amino groups.
• In the cytosol of hepatocytes, amino groups from most amino acids
are transferred to -ketoglutarate to form glutamate, which enters
mitochondria and gives up its amino group to form NH+4.
Wednesday, July 26, 2017 16
17. Metabolic Fates of Amino Groups
• Excess ammonia generated in most other tissues is converted to the
amide nitrogen of glutamine, which passes to the liver, then into liver
mitochondria.
• Glutamine or glutamate or both are present in higher concentrations
than other amino acids in most tissues.
• In skeletal muscle, excess amino groups are generally transferred to
pyruvate to form alanine, another important molecule in the
transport of amino groups to the liver.
Wednesday, July 26, 2017 17
18. Ammonia has to be eliminated
• Ammonia is toxic, especially for the CNS, because it reacts with -
keto glutarate to from glutamate, thus making it limiting for the TCA
cycle decrease in the ATP level.
• Liver damage or metabolic disorders associated with elevated
ammonia can lead to tremor, slurred speech, blurred vision, coma,
and death
• Normal conc. of ammonia in blood: 19- 87 ug /dl
Wednesday, July 26, 2017 18
19. Nitrogen removal from amino acids
Transamination
Oxidative
deamination
Urea cycle
Aminotransferase
PLP
Wednesday, July 26, 2017 19
20. Nitrogen removal from amino acids
Step 1: Remove amino group
Step 2: Take amino group to liver for nitrogen excretion
Step 3: Entry into mitochondria
Step 4: Prepare nitrogen to enter urea cycle
Step 5: Urea cycle
Wednesday, July 26, 2017 20
21. Nitrogen carriers
1. Glutamate
• Transfers one amino group WITHIN cells:
• Aminotransferase → makes glutamate from -ketoglutarate
• Aminotransferase (PLP) → -ketoglutarate → glutamate
• Glutamate ddehydrogenase → opposite
• Glutamate dehydrogenase (no PLP) → glutamate → -ketoglutarate (in liver)
2. Glutamine
Transfers two amino group BETWEEN cells → releases its amino group in
the liver
• Glutamine synthase → glutamate → glutamine
• Glutaminase → glutamine → glutamate (in liver)
3. Alanine
Transfers amino group from tissue (muscle) into the liver
Wednesday, July 26, 2017 21
22. Step 1: Removal of amino group
• Amino groups can be removed by
transamination
• In liver cytosol, amino groups are
passed to α-KG, forming
glutamate.
• Transaminases (aka
aminotransferases) require
pyridoxal phosphate cofactor.
Wednesday, July 26, 2017 22
23. Step 2: Take amino group to liver for nitrogen excretion(oxidative
deamination)
• Glutamate in the liver cytosol enters the
mitochondrial matrix, where its amino
group is removed by glutamate
dehydrogenase.
• The amino groups from many of the a-
amino acids are collected in the liver in
the form of the amino group of L-
glutamate molecules.
• The GDH of mammalian liver has the
unusual capacity to use either NAD+ or
NADP+ as cofactor
Glutamate
dehydrogenase
Wednesday, July 26, 2017 23
24. Transport of amino groups as glutamine
• Peripheral tissues may send their
amino groups as glutamine
through the bloodstream to the
liver for processing.
To liver via bloodWednesday, July 26, 2017 24
25. Transport of amino groups as alanine (glucose-alanine cycle)
• In concert with the Cori cycle,
skeletal muscle may send
pyruvate through bloodstream
as alanine (the glucose-alanine
cycle).
• Operates when muscle proteins
are undergoing catabolism.
Wednesday, July 26, 2017 25
26. Urea formation
• Urea cycle - a cyclic pathway
of urea synthesis first
postulated by H.Krebs
• The sources of nitrogen atoms
in urea molecule:
- aspartate;
- NH4
+.
• Carbon atom comes from CO2.
Wednesday, July 26, 2017 26
27. 27
Why Urea?
• Non toxic
• Water soluble
• Combines two waste products into one molecule:
• CO2
• NH3
Wednesday, July 26, 2017
28. Production of Urea from Ammonia: The Urea Cycle
• A moderately active man consuming about 300 g of carbohydrate, 100 g of fat
and 100 g of protein daily must excrete about 16.5 g of nitrogen daily.
• 95% is eliminated by the kidneys and the remaining 5% in the faeces.
• The major pathway of N2 excretion in humans is as urea which is synthesized in
the liver, released into the blood, and cleared by the kidney.
• In humans eating an occidental diet, urea constitutes 80-90% of the nitrogen
excreted.
• The urea cycle spans two cellular compartments (It begins inside the
mitochondria of liver cells (= hepatocytes), but 3 of the steps occur in the cytosol.
• Whatever its source, the NH4+ generated in liver mitochondria is immediately
used, together with HCO–3 produced by mitochondrial respiration, to form
carbamoyl phosphate in the matrix.
• This ATP-dependent reaction is catalysed by carbamoyl phosphate synthetase I, a
regulatory enzyme present in liver mitochondria of all ureotelic organisms
including man.
• In bacteria, glutamine rather than ammonia serves as a substrate for carbamoyl
phosphate synthesis.
Wednesday, July 26, 2017 28
29. The Urea Cycle
• The carbamoyl phosphate now enters the urea cycle, which itself consists
of 4 enzymatic steps. These are:
• Step 1: Synthesis of Citrulline: Carbamoyl phosphate has a high transfer
potential because of its anhydride bond. It, therefore, donates its
carbamoyl group to ornithine to form citrulline and releases inorganic
phosphate. The reaction is catalyzed by L-ornithine transcarbamoylase of
liver mitochondria. The citrulline is released from the mitochondrion into
the cytosol.
• Step 2: Synthesis of argininosuccinate:The second amino group is
introduced from aspartate (produced in the mitochondria by
transamination and transported to the cytosol) by a condensation reaction
between the amino group of aspartate and the ureido (= carbonyl) group of
citrulline to form argininosuccinate.
• The reaction is catalyzed by argininosuccinate synthetase of the cytosol. It
requires ATP which cleaves into AMP and pyrophosphate and proceeds
through a citrullyl-AMP intermediate.
Wednesday, July 26, 2017 29
30. The Urea Cycle
• Step 3: Cleavage of argininosuccinate to arginine and fumarate:
Argininosuccinate is then reversibly cleaved by argininosuccinate lyase (=
argininosuccinase), a cold-labile enzyme of mammalian liver and kidney
tissues, to form free arginine and fumarate, which enters the pool of citric
acid cycle intermediates.
• These two reactions, which transfer the amino group of aspartate to form
arginine, preserve the carbon skeleton of aspartate in the form of
fumarate.
• Step 4: Cleavage of arginine to ornithine and urea: The arginine so
produced is cleaved by the cytosolic enzyme arginase, present in the livers
of all ureotelic organisms, to yield urea and ornithine.
• Smaller quantities of arginase also occur in renal tissue, brain, mammary
gland, testes and skin. Ornithine is, thus, regenerated and can be
transported into the mitochondrion to initiate another round of the urea
cycle.
Wednesday, July 26, 2017 30
31. Urea cycle –(Sequence of reactions)
• Carbamoyl phosphate formation in mitochondria is a prerequisite for the urea
cycle
• (Carbamoyl phosphate synthetase)
• Citrulline formation from carbamoyl phosphate and ornithine
• (Ornithine transcarbamoylase)
• Aspartate provides the additional nitrogen to form argininosuccinate in cytosol
• (Argininosuccinate synthase)
• Arginine and fumarate formation
• (Argininosuccinate lyase)
• Hydrolysis of arginine to urea and ornithine
• (Arginase)
Wednesday, July 26, 2017 31
32. The Urea Cycle
• In the urea cycle, mitochondrial and cytosolic enzymes appear to be
clustered and not randomly distributed within cellular compartments.
• The citrulline transported out of the mitochondria is not diluted into the
general pool of metabolites in the cytosol.
• Instead, each mole of citrulline is passed directly into the active site of a
molecule of argininosuccinate synthetase.
• This channeling continues for argininosuccinate, arginine and ornithine.
• Only the urea is released into the general pool within the cytosol. Thus, the
compartmentation of the urea cycle and its associated reactions is
noteworthy.
• The formation of NH4+ by glutamate dehydrogenase, its incorporation into
carbamoyl phosphate, and the subsequent synthesis of citrulline occur in
the mitochondrial matrix
• In contrast, the next 3 reactions of the urea cycle, which lead to the
formation of urea, takes place in the cytosol.
Wednesday, July 26, 2017 32
33. The Urea Cycle
• A review of the urea cycle reveals that of the 6 amino acids involved
in urea synthesis, one, N-acetylglutamate functions as an enzyme
activator rather than as an intermediate.
• The remaining 5 amino acids — aspartate, arginine, ornithine,
citrulline and argininosuccinate — all function as carriers of atoms
which ultimately become urea.
• Two (aspartate and arginine) occur in proteins, while the remaining
three (ornithine, citrulline and argininosuccinate) do not.
• The major metabolic roles of these latter 3 amino acids in mammals is
urea synthesis
• Note that urea formation is, in part, a cyclical process. The ornithine
used in Step 1 is regenerated in Step 4.
Wednesday, July 26, 2017 33
34. Step 3: entry of nitrogen to mitochondria
Wednesday, July 26, 2017 34
35. Step 4: prepare nitrogen to enter urea cycle
Regulation
Wednesday, July 26, 2017 35
37. OOA
The citric acid cycle and the urea cycle are linked(Krebs’ bicycle)
Wednesday, July 26, 2017 37
38. The overall chemical balance of the biosynthesis of urea
NH3 + CO2 + 2ATP → carbamoyl phosphate + 2ADP + Pi
Carbamoyl phosphate + ornithine → citrulline + Pi
Citrulline + ATP + aspartate → argininosuccinate + AMP + PPi
Argininosuccinate → arginine + fumarate
Arginine → urea + ornithine
Wednesday, July 26, 2017 38
39. Regulation of urea cycle
The activity of urea cycle is regulated at two levels:
• Dietary intake of proteins much urea (amino acids are used for fuel)
• Prolonged starvation break down of muscle proteins much urea also
• The rate of synthesis of four urea cycle enzymes and carbamoyl phosphate
synthetase I (CPS-I) in the liver is regulated by changes in demand for urea cycle
activity.
• Enzymes are synthesized at higher rates in animals during:
• starvation
• in very high protein diet
• Enzymes are synthesized at lower rates in
• well-fed animals with carbohydrate and fat diet
• animals with protein-free diets
Wednesday, July 26, 2017 39
40. Ammonia toxicity
• Ammonia encephalopathy : Increased concentration of ammonia
in the blood and other biological fluids → ammonia diffuses into cells,
across blood/brain barrier → increased synthesis of glutamate from
a-ketoglutarate, increased synthesis of glutamine
• a-ketoglutarate is depleted from CNS → inhibition of TCA cycle and
production of ATP
• Neurotransmitters – glutamate (excitatory neurotr.) and GABA
(inhibitory neurotr.), may contribute to the CNS effects ?
Wednesday, July 26, 2017 40
41. Deficiencies of urea cycle enzymes
• The synthesis of urea in the liver is the major pathway of the removal of NH4+.
• A blockage of carbamoyl phosphate synthesis or any of the 4 steps of the urea
cycle has serious consequences because there is no alternative pathway for the
synthesis of urea.
• They all lead to an elevated level of NH4+ in the blood (hyperammonemia) and
encephalopathy.
• Some of these genetic defects become evident a day or two after birth, when the
afflicted infant becomes lethargic and vomits periodically.
• Coma and irreversible brain damage may ensue.
Wednesday, July 26, 2017 41
43. Fates of carbon skeleton
• Based on their catabolic products, amino acids are classified as glucogenic or
ketogenic.
• Those amino acids that generate precursors of glucose, e.g., pyruvate or citric
acid cycle intermediate (i.e., α-ketoglutarate, succinyl-CoA, fumarate or
oxaloacetate), are referred to as glucogenic. Ala, Arg, Asn, Asp, Cys, Gln, Glu, Gly,
His, Met, Pro, Ser, Thr and Val belong to this category.
• Those amino acids that are degraded to acetyl-CoA or acetoacetyl-CoA are
termed as ketogenic because they give rise to ketone bodies.
• Their ability to form ketones is particularly evident in untreated diabetes mellitus,
in which large amounts of ketones are produced by the liver, not only from fatty
acids but from the ketogenic amino acids.
• Leucine (Leu) exclusively belongs to this category.
• The remaining 5 amino acids (Ile, Lys, Phe, Trp and Tyr) are both glucogenic and
ketogenic.
• Some of their carbon atoms emerge in acetyl-CoA or acetoacetyl-CoA, whereas
others appear in potential precursors of glucose.
Wednesday, July 26, 2017 43