The document discusses amino acid metabolism. It covers:
1) Transamination is the transfer of an amino group between amino acids and keto acids using pyridoxal phosphate as a cofactor. This reaction converts non-essential amino acids and diverts excess amino acids to energy production.
2) Glutamate undergoes oxidative deamination to liberate ammonia for urea synthesis. Urea synthesis involves carbamoyl phosphate synthase I catalyzing the first step.
3) Methionine is activated to form S-adenosylmethionine, which donates methyl groups in transmethylation reactions like cysteine synthesis from homocysteine and serine.
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
Fate of Glucogenic and Ketogenic amino acid
Amino acid are the currency of of nitrogen and protein economy of the host, hence they are used in many pathways beyond protein synthesis, including energy production and neurotransmitter synthesis.
All amino acid are comprised of an amino group and a carbon skeleton. During metabolism these two parts are separated as they have different ‘fates’
Of the liberated amino acid approximately 75% are utilized while remainder serve as precursors for important biological compound and those not utilized are degraded to amphibolic intermediates
The pathway of amino acid catabolism is quite similar in most organism
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
Fate of Glucogenic and Ketogenic amino acid
Amino acid are the currency of of nitrogen and protein economy of the host, hence they are used in many pathways beyond protein synthesis, including energy production and neurotransmitter synthesis.
All amino acid are comprised of an amino group and a carbon skeleton. During metabolism these two parts are separated as they have different ‘fates’
Of the liberated amino acid approximately 75% are utilized while remainder serve as precursors for important biological compound and those not utilized are degraded to amphibolic intermediates
The pathway of amino acid catabolism is quite similar in most organism
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.
Biosynthesis of different types of amino acids.pptxlaija s. nair
Amino acids are the building blocks of proteins, playing a crucial role in various biological processes. They are categorized into essential and non-essential amino acids based on the body's ability to synthesize them. While essential amino acids must be obtained through the diet, non-essential amino acids can be synthesized by the body.
General Pathway of Amino Acid Biosynthesis:
Amino acid biosynthesis involves complex metabolic pathways that differ for each amino acid. However, a general overview can be provided:
Carbon Skeleton Formation:
Amino acids are composed of a central carbon atom (alpha carbon) bonded to a hydrogen atom, an amino group (NH2), a carboxyl group (COOH), and a side chain (R group) specific to each amino acid.
The carbon skeletons of amino acids are derived from intermediates of glycolysis, citric acid cycle, and pentose phosphate pathway.
Transamination:
A crucial step in amino acid biosynthesis is the transamination reaction, where an amino group is transferred from an amino acid donor to an alpha-keto acid acceptor.
This reaction is catalyzed by aminotransferases or transaminases, and pyridoxal phosphate (PLP) acts as a cofactor.
Specific Pathways for Essential Amino Acids:
Essential amino acids, which cannot be synthesized de novo by the body, have specific biosynthetic pathways.
For example, lysine and methionine biosynthesis involve the aspartate family pathway, while valine, leucine, and isoleucine biosynthesis occur through the branched-chain amino acid (BCAA) pathway.
Non-Essential Amino Acid Biosynthesis:
Non-essential amino acids can be synthesized by the body through various pathways.
For instance, glutamate serves as a precursor for the synthesis of several amino acids, including proline, arginine, and ornithine.
Specific Amino Acid Biosynthesis Pathways:
Serine and Glycine Biosynthesis:
Serine is derived from 3-phosphoglycerate and can be converted to glycine.
The enzyme serine hydroxymethyltransferase plays a key role in interconverting serine and glycine.
Histidine Biosynthesis:
Histidine biosynthesis involves a unique pathway that starts with phosphoribosyl pyrophosphate (PRPP) and includes several enzymatic steps.
Tyrosine and Phenylalanine Biosynthesis:
The shikimate pathway is essential for the biosynthesis of aromatic amino acids, including tyrosine and phenylalanine.
Chorismate is a key intermediate in this pathway.
Arginine Biosynthesis:
Arginine biosynthesis involves the urea cycle and the ornithine biosynthetic pathway.
Citrulline serves as a key intermediate in these processes.
Proline Biosynthesis:
Proline is derived from glutamate through a two-step reduction process involving pyrroline-5-carboxylate (P5C).
Regulation of Amino Acid Biosynthesis:
Amino acid biosynthesis is tightly regulated to maintain a balance between the body's requirements and energy conservation.
Feedback inhibition and genetic regulation play key roles in controlling the activity of enzymes involved in these p
Protein metabolism is more appropriately learnt as metabolism of Amino acid. The proteins on degradation(proteolysis) release individual amino acids. The amount of free amino acids distributed throught the body is called Amino acid pool. The amino acids undergo certain common reactions like transamination followed by deamination for the liberation of ammonia. The amino group of amino acids utilized for the formation of urea, which is the end product of protein metabolism
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.
Overview of amino acid anabolism and catabolism and fate of ammonia in amino acid metabolism. This is targeted for MBBS, MD, BDS and general Biochemistry students
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.
Formation and fate of Ammonia
Transdeamination, oxidative and non oxidative deamination, Ammonia transport, Ammonia intoxication, Ammonia detoxification
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.
Biosynthesis of different types of amino acids.pptxlaija s. nair
Amino acids are the building blocks of proteins, playing a crucial role in various biological processes. They are categorized into essential and non-essential amino acids based on the body's ability to synthesize them. While essential amino acids must be obtained through the diet, non-essential amino acids can be synthesized by the body.
General Pathway of Amino Acid Biosynthesis:
Amino acid biosynthesis involves complex metabolic pathways that differ for each amino acid. However, a general overview can be provided:
Carbon Skeleton Formation:
Amino acids are composed of a central carbon atom (alpha carbon) bonded to a hydrogen atom, an amino group (NH2), a carboxyl group (COOH), and a side chain (R group) specific to each amino acid.
The carbon skeletons of amino acids are derived from intermediates of glycolysis, citric acid cycle, and pentose phosphate pathway.
Transamination:
A crucial step in amino acid biosynthesis is the transamination reaction, where an amino group is transferred from an amino acid donor to an alpha-keto acid acceptor.
This reaction is catalyzed by aminotransferases or transaminases, and pyridoxal phosphate (PLP) acts as a cofactor.
Specific Pathways for Essential Amino Acids:
Essential amino acids, which cannot be synthesized de novo by the body, have specific biosynthetic pathways.
For example, lysine and methionine biosynthesis involve the aspartate family pathway, while valine, leucine, and isoleucine biosynthesis occur through the branched-chain amino acid (BCAA) pathway.
Non-Essential Amino Acid Biosynthesis:
Non-essential amino acids can be synthesized by the body through various pathways.
For instance, glutamate serves as a precursor for the synthesis of several amino acids, including proline, arginine, and ornithine.
Specific Amino Acid Biosynthesis Pathways:
Serine and Glycine Biosynthesis:
Serine is derived from 3-phosphoglycerate and can be converted to glycine.
The enzyme serine hydroxymethyltransferase plays a key role in interconverting serine and glycine.
Histidine Biosynthesis:
Histidine biosynthesis involves a unique pathway that starts with phosphoribosyl pyrophosphate (PRPP) and includes several enzymatic steps.
Tyrosine and Phenylalanine Biosynthesis:
The shikimate pathway is essential for the biosynthesis of aromatic amino acids, including tyrosine and phenylalanine.
Chorismate is a key intermediate in this pathway.
Arginine Biosynthesis:
Arginine biosynthesis involves the urea cycle and the ornithine biosynthetic pathway.
Citrulline serves as a key intermediate in these processes.
Proline Biosynthesis:
Proline is derived from glutamate through a two-step reduction process involving pyrroline-5-carboxylate (P5C).
Regulation of Amino Acid Biosynthesis:
Amino acid biosynthesis is tightly regulated to maintain a balance between the body's requirements and energy conservation.
Feedback inhibition and genetic regulation play key roles in controlling the activity of enzymes involved in these p
Protein metabolism is more appropriately learnt as metabolism of Amino acid. The proteins on degradation(proteolysis) release individual amino acids. The amount of free amino acids distributed throught the body is called Amino acid pool. The amino acids undergo certain common reactions like transamination followed by deamination for the liberation of ammonia. The amino group of amino acids utilized for the formation of urea, which is the end product of protein metabolism
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.
Overview of amino acid anabolism and catabolism and fate of ammonia in amino acid metabolism. This is targeted for MBBS, MD, BDS and general Biochemistry students
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.
Formation and fate of Ammonia
Transdeamination, oxidative and non oxidative deamination, Ammonia transport, Ammonia intoxication, Ammonia detoxification
Similar to CC 8 SEM 4 AMINO ACID METABOLISM.pdf Shilpa Dutta (20)
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
2. INTRODUCTION
• Proteins are the most abundant organic compounds and constitute a
major part of the body (10-12 kg in adults).
• About half of the body protein (collegen) is present in the supportive
tissue (skeleton and connective) while the other half is intercellular.
• Proteins are nitrogen containing macromolecule consisting L- alpha-
amino acids . of the 20 amino acids found in proteins, half can be
synthesized by the body (non-essential) while the rest have to
provided in diet (essential amino acids).
• The protein on degradation (proteolysis) release amino acids.
3. AMINO ACID POOL
An adult has about 100 g of free
amino acids which represent the
amino acid pool of the body.
• Glutamate and glutamine
together constitute about 50% ,
and essential amino acids about
10 % of the body pool.
4. 1.Sources of amino acid [AA] pool
-protein turnover (daily 300-400g of protein degraded to
Amino acid)
-dietary protein
-synthesis of non-essential Amino acids.
2.Utilization of AA from body pool
-Amino acids are converted into carbohydrates and fats.
-generally, about 10-15% of body energy requirements are
gained from the Amino acids.
-many important nitrogenous compounds (porphyrins,
purins, pyrimidins) are produced from Amino acids
-most of body proteins (300-400 g/daily) are synthesized
from Amino acid pool.
5. General Aspects of Amino Acids Metabolism.
There is a primitive pathways of AA fate
degradation:
1.fate of α-amino group is convertation into
ammonium ion (by oxidative deamination
Glutamate)
2.fate of carbon atoms which mostly turn into
energy:
-the C3 family of AA (Alanine, Serine, and
Cysteine) are converted into Pyruvate;
-the C4 family of AA (Aspartate and Asparagine)
are converted into Oxaloacetate;
-the C5 family of AA (Glutamine, Proline,
Arginine, Histidine) into α-ketoglutarate
throught Glutamate;
6. The amino acids are classified into two groups based on the
nature of metabolic end products of carbon skeleton
7. the Amino acid undergo certain common reactions
transamination followed by
deamination for the liberation of
ammonia.
The amino group of the amino
acids is utilized for the formation
of urea which is an excretory end
product of protein metamolism.
8. Transamination
Transamination is a transfer of an amino (-NH2 ) group
from an amino acid to a keto acid by transaminase
(recently, aminotransferases).
• All transaminases require pyridoxal phosphate (PLP)
• Specific transaminases exist for each pair of amino and
keto acids. aspartate and alanine transaminase make
significant contribution for transamination.
• There is no free NH3.
• Reversible.
• Production of non-essential amino group.
• Diverts excess amino acids towards energy generation.
• The amino acid undergo transamination to finally
concentrate nitrogen in glutamate.
Glutamate is the only amino acid that undergoes oxidative
deamination to liberate free NH3 for urea synthesis.
9. MECHANISM OF TRANSAMINATION
PING PONG mechanism:
Transamination occurs in two stages:
A) Transfer of amino group to the
coenzyme pyridoxal phosphate
(bound to the coenzyme) to form
pyridoxamine phosphate.
B) The amino group of
pyridoxamine phosphate is then
transfer to a keto acid to produce
a new amino acid and the
enzyme with PLP is regenerated.
11. OXIDATIVE DEAMINATION
1. Oxidative deamination- it is the liberation of free ammonia from the
amino group of amino acids coupled with oxidation.
-it takes place mostly in liver and kidney.
-to provide ammonium for urea cycle.
-to provide alpha keto acid for energy generation.
12. Non-oxidative deamination
1. Non-oxidative deamination- some of the
amino acids can be deaminated to
liberate NH3 without undergo oxidation.
a. amino acids dehydrases (serine, threonine and
homoserine – are hydroxy AA deamination of
which is catalysed by pyridoxal phosphate [PLP])
b. sulfur amino acids (cystein, homocystein) undergo
deamination coupled with desulfhydrases
c. dehydratation of histidine is catalised by histidase
14. BIOSYNTHESIS OF NITRIC OXIDE (NO)
• NO is synthesized from Arginine.
• The enzyme nitric oxide synthase cleaves the nitrogen from the arginine to form NO.
• This reaction require NADPH, FMN, FAD, heme and tetrahydrobiopterin.
15. TRANSMETHYLATION
The transfer of methyl group from active methionine to an acceptor is
known as transmethylation.
Methionine has to be activated to S-adenosylmethionine(SAM) or active
methionine to donate the methyl group.
Formation of active-methionine:-
1. the synthesis of S-adenosylmethionine occurs by the transfer of an
adenosyl group from ATP to sulfer atom of methionine. This reaction
is catalysed by methionine S-adenosylmethionine transferase.
2. The activation of methionine is unique as the sulfer becomes a
sulfonium atom (SAM is a sulfonium compound) by the addition of a
third carbon.
3. This reaction is also unusual since all the three phosphates of ATP
are elimined as pyrophosphate (PPi) and inorganic phosphate (Pi) .
4. Three high energy phosphate (3 ATP) are consumed in the formation
of SAM.
16. Amino acid metabolism
1. What is general amino acid pool? (1/2015)(1/2013)
2. What is transmethylation? Give one example. (2/2015)(2/2013)
3. Discuss the biosynthesis of nitric oxide. Mention its physiological significance.(2/2015)(4/2013) (3+2/2022)
4. Mention two important amino acids decarboxylation reactions. (2/2015)
5. Discuss the role of PLP in transamination reaction. (3/2014)(3/2012)
6. How is ‘active-methionine’ formed? (2/2021)
7. What are glucogenic aminoacids? Give example. (1+1/2014)
8. Why in deamination reaction the enzymes are termed as deaminase? (2/2011)
9. Describe the reaction catalyzed by L-glutamate dehydrogenase and mention its significance. (4/2021)
10. Transamination process of amino acid. (5/2022)
11. Name two amino acids which are both glucogenic and ketogenic in nature. (1/2022)
17. Q.Discuss the role of PLP in transamination reaction. (3/2014)(3/2012)
• All the transaminases require pyridoxal phosphate (PLP), a derivative of vitamin B6.
• the aldehyde group of PLP is linked with ε- amino acid of lysine residue, at the active site of the enzyme
forming a Schiff base (imine linkage).
• When an amino acid comes in contact with the enzyme, it displaces lysine and a new Schiff base
linkage is formed.
• The amino-acid-PLP-shiff base tightly binds with the enzyme by non-covalent forces.
Q. Why in deamination reaction the enzymes are termed as deaminase?
• deaminases help to remove α amino group from amino acid.
• Amino group is converted into ammonia while the amino acid itself converts into its corresponding keto acid.
This Enzymes catalyse this reaction that’s why they are called deaminases.
18. reaction catalyzed by L-glutamate dehydrogenase
significance
• GDH catalysed reaction is important as it
reversibly links up glutamate metabolism with
TCA cycle through alpha-ketoglutarate.
• GDH is involved in boyh catabolic and anabolic
reactions.
Q. Describe the reaction catalyzed by L-glutamate dehydrogenase and mention its significance. (4/2021)
19. METABOLISM OF GLYCINE:
Q. Discuss the synthesis glycine from choline.
• Betaine, formed by two successive oxidation of choline.
• It may transfer one of its labile methyl groups to
homocysteine to change itself to dimethylglycine.
• The latter is then oxidized through sarcosine to glycine.
Q. Discuss the role of folate in glycine metabolism.
• Glycine is synthesized from serine by the enzyme serine
hydroxymethyl transferase which is depend on
tetrahydrofolate (THF).
• Glycine synthase can convert a one carbon unit (N^5,N^10-
methylene THF), co2 and NH3 to glycine.
20. METABOLISM OF TRYPTOPHAN
Q. Discuss how L-tryptophan is converted to pyruvate. (5/2015)
• Tryptophan 2,3- dioxygenase, oxidizes tryptophan to N-formylkunurine
• N-formylkunurine is deformylated by kynurine formylase to kynurenine.
• Kynurenine is hydroxylated by kynurenine hydroxylase to 3-hydroxykynurenine.
• 3-hydroxykynurenine is cleaved by PLP-dependent kynureninase into 3-hydroxyanthranilate and alanine.
• Alanine transaminated to pyruvate.
21. Q. Discuss the catabolism of phenylalanine leading to the formation of fumerate and acetoacetate.
(5/2013)
22. METABOLISM OF S-CONTAINING AMINO ACID:
Q. Discuss the synthesis and significance of cysteine. (4/2013)
Synthesis of cysteine:-
• Mammals synthesize cysteine from two amino acids: methionine
furnishes the sulfur atom, and serine furnishes the carbon
skeleton.
• Methionine is first converted to Sadenosylmethionine, which can
lose its methyl group to any of a number of acceptors to form S-
adenosylhomocysteine (adoHcy).
• This demethylated product is hydrolyzed to free homocysteine,
which undergoes a reaction with serine, catalyzed by
cystathionine β-synthase, to yield cystathionine.
• Finally, cystathionine γ-lyase, a PLP-requiring enzyme, catalyzes
removal of ammonia and cleavage of cystathionine to yield free
cysteine.
significance of cysteine:-
• Cysteine is a non-essential amino acid important for making protein, and for other metabolic
functions.
• It's found in beta-keratin.
• This is the main protein in nails, skin, and hair.
• Cysteine is important for making collagen.
24. UREA SYNTHESIS:
Q. Discuss the role of carbamoyl synthase- I in
relation to urea formation.
• carbamoyl phosphate synthase I (CPS I) of
mitochondria catalyses the condensation of
NH4+ ions with C02 to form carbamoyl
phosphate.
• This step consumes two ATP and is irreversible
and rate limiting.
• CPS I requires N- acetylglutamate for its activity.
25. GLUTATHIONE SYNTHESIS:
Q. Discuss the synthesis and significance of
glutathione. (4/2012)(5/2011)
Glutathione is a tripeptide consist with ( γ-glutamyl-
cysteinyl-glycine) and require three amino acids for
its formation.