Enzymes are biomolecules that catalyze chemical reactions and increase their rates. They have high catalytic power, increasing reaction rates by factors of 108 to 1020. Enzymes also exhibit specificity, only catalyzing certain reactions and acting on specific substrates. Regulation of enzyme activity ensures metabolic reactions proceed at appropriate rates. Enzymes are classified based on the type of reaction they catalyze and given four-digit codes describing their functions. They have complex three-dimensional structures essential for catalytic activity and often require cofactors to function properly.
Introduction, Nomenclature of enzymes, Classification of enzymes on the basis of site of action, on the reaction of catalysis and Classification depends upon substrates on they which act, Specificity of Enzymes, Active Site of An Enzyme: 1. Lock-key model 2. Induce fit model, Factors Affecting Enzymes Reaction, Enzyme 1.Inhibition Competitive inhibition, 2. Non-Competitive inhibition, Isoenzymes, Allosteric Enzymes, Co-Factors, Turnover Number of An Enzyme, Pharmaceutical Importance Of Enzymes,
Introduction, Nomenclature of enzymes, Classification of enzymes on the basis of site of action, on the reaction of catalysis and Classification depends upon substrates on they which act, Specificity of Enzymes, Active Site of An Enzyme: 1. Lock-key model 2. Induce fit model, Factors Affecting Enzymes Reaction, Enzyme 1.Inhibition Competitive inhibition, 2. Non-Competitive inhibition, Isoenzymes, Allosteric Enzymes, Co-Factors, Turnover Number of An Enzyme, Pharmaceutical Importance Of Enzymes,
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enzyme
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enzyme
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Last Updated: Mar 4, 2024 • Article History
Top Questions
What is an enzyme?
What are enzymes composed of?
What are examples of enzymes?
What factors affect enzyme activity?
Summary
Read a brief summary of this topic
Enzyme, a substance that acts as a catalyst in living organisms, regulating the rate at which chemical reactions proceed without itself being altered in the process.
In the induced-fit theory of enzyme-substrate binding, a substrate approaches the surface of an enzyme (step 1 in box A, B, C) and causes a change in the enzyme shape that results in the correct alignment of the catalytic groups (triangles A and B; circles C and D represent substrate-binding groups on the enzyme that are essential for catalytic activity). The catalytic groups react with the substrate to form products (step 2). The products then separate from the enzyme, freeing it to repeat the sequence (step 3). Boxes D and E represent examples of molecules that are too large or too small for proper catalytic alignment. Boxes F and G demonstrate binding of an inhibitor molecule (I and I′) to an allosteric site, thereby preventing interaction of the enzyme with the substrate. Box H illustrates binding of an allosteric activator (X), a nonsubstrate molecule capable of reacting with the enzyme.
enzyme
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Category: Science & Tech
Key People: Richard Henderson Emil Fischer Maud Leonora Menten Günter Blobel Arieh Warshel
Related Topics: neuraminidase renin-angiotensin system allosteric control induction cooperativity
A brief treatment of enzymes follows. For full treatment, see protein: Enzymes.
The biological processes that occur within all living organisms are chemical reactions, and most are regulated by enzymes. Without enzymes, many of these reactions would not take place at a perceptible rate. Enzymes catalyze all aspects of cell metabolism. This includes the digestion of food, in which large nutrient molecules (such as proteins, carbohydrates, and fats) are broken down into smaller molecules; the conservation and transformation of chemical energy; and the construction of cellular macromolecules from smaller precursors. Many inherited human diseases, such as albinism and phenylketonuria, result from a deficiency of a particular enzyme.
rennet in cheese making
rennet in cheese making
Rennet, which contains the protease enzyme chymosin, being added to milk during cheese making.
Enzymes also have valuable industrial and medical applications. The fermenting of wine, leavening of bread, curdling of cheese, and brewing of beer have been practiced from earliest times, but not until the 19th century were these reactions understood to be the result of the catalytic activity of enzymes. Since then, enzymes han
Introduction
Definition
Historical aspects
Nomenclature of enzymes on the basis of
1. Substrate acted
2. Reaction catalyzed
3. substrate act upon and type of reaction catalyzed
Classification of enzymes
Oxidoreductase
Transferase
Hydrolase
Lyase
Isomerase
Ligase
Property of enzyme
Structure of enzyme
Mechanism of enzyme action
Lock and key model
Induced fit model
factors affecting enzyme activity
Control of enzyme action
Conclusion
Reference
Enzymes are biological molecules (proteins) that act as catalysts and help complex reactions occur everywhere in life. Let's say you ate a piece of meat. Proteases would go to work and help break down the peptide bonds between the amino acids.
Encyclopedia Britannica
HomeGames & QuizzesHistory & SocietyScience & TechBiographiesAnimals & NatureGeography & TravelArts & CultureMoneyVideos
enzyme
Home
Health & Medicine
Anatomy & Physiology
Science & Tech
enzyme
biochemistry
Written and fact-checked by
Last Updated: Mar 4, 2024 • Article History
Top Questions
What is an enzyme?
What are enzymes composed of?
What are examples of enzymes?
What factors affect enzyme activity?
Summary
Read a brief summary of this topic
Enzyme, a substance that acts as a catalyst in living organisms, regulating the rate at which chemical reactions proceed without itself being altered in the process.
In the induced-fit theory of enzyme-substrate binding, a substrate approaches the surface of an enzyme (step 1 in box A, B, C) and causes a change in the enzyme shape that results in the correct alignment of the catalytic groups (triangles A and B; circles C and D represent substrate-binding groups on the enzyme that are essential for catalytic activity). The catalytic groups react with the substrate to form products (step 2). The products then separate from the enzyme, freeing it to repeat the sequence (step 3). Boxes D and E represent examples of molecules that are too large or too small for proper catalytic alignment. Boxes F and G demonstrate binding of an inhibitor molecule (I and I′) to an allosteric site, thereby preventing interaction of the enzyme with the substrate. Box H illustrates binding of an allosteric activator (X), a nonsubstrate molecule capable of reacting with the enzyme.
enzyme
See all media
Category: Science & Tech
Key People: Richard Henderson Emil Fischer Maud Leonora Menten Günter Blobel Arieh Warshel
Related Topics: neuraminidase renin-angiotensin system allosteric control induction cooperativity
A brief treatment of enzymes follows. For full treatment, see protein: Enzymes.
The biological processes that occur within all living organisms are chemical reactions, and most are regulated by enzymes. Without enzymes, many of these reactions would not take place at a perceptible rate. Enzymes catalyze all aspects of cell metabolism. This includes the digestion of food, in which large nutrient molecules (such as proteins, carbohydrates, and fats) are broken down into smaller molecules; the conservation and transformation of chemical energy; and the construction of cellular macromolecules from smaller precursors. Many inherited human diseases, such as albinism and phenylketonuria, result from a deficiency of a particular enzyme.
rennet in cheese making
rennet in cheese making
Rennet, which contains the protease enzyme chymosin, being added to milk during cheese making.
Enzymes also have valuable industrial and medical applications. The fermenting of wine, leavening of bread, curdling of cheese, and brewing of beer have been practiced from earliest times, but not until the 19th century were these reactions understood to be the result of the catalytic activity of enzymes. Since then, enzymes han
Introduction
Definition
Historical aspects
Nomenclature of enzymes on the basis of
1. Substrate acted
2. Reaction catalyzed
3. substrate act upon and type of reaction catalyzed
Classification of enzymes
Oxidoreductase
Transferase
Hydrolase
Lyase
Isomerase
Ligase
Property of enzyme
Structure of enzyme
Mechanism of enzyme action
Lock and key model
Induced fit model
factors affecting enzyme activity
Control of enzyme action
Conclusion
Reference
Enzymes are biological molecules (proteins) that act as catalysts and help complex reactions occur everywhere in life. Let's say you ate a piece of meat. Proteases would go to work and help break down the peptide bonds between the amino acids.
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2. ENZYMES
Definitions--
A biomolecule either Protein or RNA, that catalyse a
specific chemical reaction, enhance the rate of a
reaction by providing a reaction path with a lower
activation energy
3. Fundamental Properties
1) Catalytic power-speeding up reactions 108 to
1020 fold.
They speed up reactions without being
used up.
2) Specificity
a) for substrate - ranges from absolute to relative
b) for reaction catalyzed
3) Regulated-- some enzymes can sense metabolic
signals.
4. Catalytic Power
Catalytic Power is defined as the Ratio of the Enzyme-Catalyzed Rate of a
Reaction to the Uncatalyzed Rate
e.g. Urease-
At 20°C, the rate constant for the enzyme-
catalyzed reaction is 3 X 104/sec
the rate constant for the uncatalyzed hydrolysis
of urea is 3 X 1010/sec
1014 is the ratio of the catalyzed rate to the
uncatalyzed rate of reaction
5. Specificity
Defined as the Selectivity of Enzymes for the Reactants Upon which They Act
In an enzyme-catalyzed reaction, none of the substrate is diverted into
nonproductive side reactions, so no wasteful by-products are produced.
6. The substances upon which an enzyme acts are
traditionally called- substrates
The selective qualities of an enzyme are collectively
recognized- specificity
The specific site on the enzyme where substrate binds and
catalysis occurs is called- active site
7. Regulation
Regulation of Enzyme Activity Ensures That the Rate of Metabolic Reactions Is
Appropriate to Cellular Requirements
essential to the integration and regulation of metabolism
Achieved by various ways
Inhibitor
Activator
Hormonal
Rate of synthesis
8. History
As early as the late 1700s and early 1800s, the digestion
of meat by stomach secretions and the conversion of
starch to sugars by plant extracts and saliva were
known. However, the mechanism by which this occurred
had not been identified
9. In the 19th century, when studying the fermentation of sugar to alcohol by
yeast, Louis Pasteur came to the conclusion that this fermentation was
catalyzed by a vital force contained within the yeast cells called
"ferments", which were thought to function only within living organisms.
He wrote that "alcoholic fermentation is an act correlated with the life
and organization of the yeast cells, not with the death or putrefaction of
the cells.
10. In 1878 German physiologist Wilhelm Kühne (1837–1900) first
used the term enzyme. The word enzyme was used later to
refer to nonliving substances such as pepsin, and the word
ferment used to refer to chemical activity produced by living
organisms
In 1897 Eduard Buchner began to study the ability of yeast
extracts that lacked any living yeast cells to ferment sugar.
In a series of experiments at the University of Berlin, he
found that the sugar was fermented even when there were
no living yeast cells in the mixture
He named the enzyme that brought about the fermentation
of sucrose "zymase". In 1907 he received the Nobel Prize in
Chemistry“ for his biochemical research and his discovery of
cell-free fermentation"
12. 2. Names bearing little resemblance to their activity
e.g. catalase - the peroxide-decomposing enzyme
Proteolytic enzymes (proteases) of the digestive tract
Trypsin- Gr. Word Tryein means to wear down
Pepsin- Pepsis means digestion
13. IUB nomemclature
1956 - to create a systematic basis for enzyme nomenclature
4 digit numbered code
first digit - major class
Second digit - sub class
third digit - sub sub class
final digit - specific enzyme
14. 2.7.1.1
ATP: glucose phosphotransferase
2- class name (transferase)
7- subclass name (phosphotransferase)
1- sub sub class (hydroxyl group as acceptor)
1- specific enzyme (D- glucose as phosphoryl group
acceptor)
15. Enzyme classification
Six classes
1. Oxidoreductase- transfer of reducing equivalents from
one redox system to another
e.g. Alcohol Dehydrogenase
Lactate dehydrogenase
cytochrome oxidase
17. 3. Hydrolase
cleave C-O, C-N, C-S or P-O etc bonds by adding water
across the bond
e.g. lipase
acid phosphatase
(important in digestive process)
18. 4. Lyases
cleave C-O, C-N, or C-S bonds but do so without addition of
water and without oxidizing or reducing the substrates
e.g. aldolase
fumarase
Carbonic anhydrase
19. 5. Isomerase
catalyze intramolecular rearrangements of functional
groups that reversibly interconvert to optical or
geometric isomers
e.g. Triose isomerase
phosphohexose isomerase
mutase
20. 6. Ligase
catalyze biosynthetic reactions that form a covalent bond
between two substrates utilizing ATP-ADP
interconversion
e.g. glutamine synthetase
DNA- ligase
21. Specificity
highly specific compared to other catalyst
catalyzes only specific reaction
3 types
1. Stereospecificity/ optical specificity
2. Reaction specificity
3. Substrate specificity
22. Optical specificity
able to recognise optical isomers of the substrate
Act only on one isomer
e.g. enzymes of amino acid metabolism (D & L Amino acid
oxidase)
Isomerase do not exhibit stereospecificity
23. Reaction Specificity
catalyze only one specific reaction over substrate
e.g. amino acid can undergo deamination, transamination,
decarboxylation and each is catalysed by separate
enzyme
24. Substrate specificity
specific towards their substrates
e.g. glucokinase and galactokinase- both transfer phophoryl
group from ATP to different molecule
3 types
a. Absolute
b. Relative substrate
c. broad
26. Relative substrate specificity
act on structurally related substrates
Further divide into
i. Group dependent- act on specific group e.g. trypsin-
break peptide bond between lysine and arginine,
Chymotripsin act on aromatic AA
ii. Bond specificity- act on specific bond e.g. proteolytic
enzyme, glycosidase
28. Chemical Nature &
Properties of Enzyme
Protein or RNA
Tertiary structure and specific conformation- essential
for catalytic power
Holoenzyme- functional unit
Apoenzyme & coenzyme
29. Prosthetic group Coenzyme/cofactor
Non protein molecule Non protein molecule
Tightly (covalently)
bound
Loosely bound
Stable incorporation Dissociable
Cannot be dissociated Seperable by dialysis
etc
30. Monomeric Enzyme- made of a single
polypeptide e.g. ribonuclease, trypsin
Oligomeric Enzyme- more than one
polypeptide e.g. LDH, aspartate
carbamoylase
Multienzyme complex- specific sites to
catalyse different reactions in sequence.
Only native conformation is active not
individual e.g. pyruvate dehydrogenase
31. Multienzyme Complexes and
Multifunctional Enzymes
In a number of metabolic pathways, several
enzymes which catalyze different stages of
the process have been found to be
associated noncovalently, giving a
multienzyme complex.
Examples: Pyruvate Dehydrogenase Complex;
Electron Respiratory Chain
In other cases, different activities may be
found on a single multifunctional polypeptide
chain. The presence of multiple activities is
on a single polypeptide chain is usually the
result of a gene fusion event
