Prepared by
Dr. Shraddha Shrivastava
Assistant Professor
Division of Veterinary Biochemistry
Deptt of Veterinary Physiology & Biochemistry
Co.V.Sc. & A.H., Jabalpur
Index
1. Definition
2. History
3. Importance
4. Properties
5. Classification
6. Different classes of enzymes
7. Nomenclature
8. Individual class of enzymes
The study of enzymes is called enzymology
Definition
Biological catalysts
Accelerates the rate of chemical reactions
Capable of performing multiple reactions (recycled)
Final distribution of reactants and products governed
by equilibrium properties
Enzymes are biological catalysts –
Proteins, (a few RNA exceptions)
Orders of magnitude faster than chemical catalysts -
Act under mild conditions (temperature and pressure)
Highly Specific
Tightly Regulated
History
Berzelius in 1836 coined the term catalysis (Gk: to
dissolve).
In 1878, Kuhne used the word enzyme (Gk: in yeast) to
indicate the catalysis taking place in the biological
systems.
lsolation of enzyme system from cell-free extract of
yeast was achieved in 1883 by Buchner. He named the
active principle as zymase (later found to contain a
mixture of enzymes), which could convert sugar to
alcohol.
ln 1926, James sumner first achieved the isolation and
crystallization of enzyme urease from jack bean.
Importance of enzymes
Enzymes are critical for every aspect of
cellular life Enzyme
Cell shape and motility
Surface receptor
Cell cycle
Metabolism
Transcription
Hormone release
Muscle contraction
Protein synthesis
Properties
Vital for chemical reactions to occur in the cell
(the breaking, forming and rearranging of bonds
on a substrate (reactant) )
Modified substrate (now a product) often
performs a different task
Consequence: ™Transformation of energy and
matter in the cell ™Cell-cell and intracellular
communication ™Allows for cellular homeostasis
to persist
Classification of Enzymes
Enzymes can be classified using a numbering
system defined by the Enzyme Commission.
This system consists of a four digit number which
classifies based on the type of reaction the
enzyme catalyzes
Different classes of enzymes
EC 1. Oxidoreductases – Transfer electrons (Redox
reactions)
EC 2. Transferases – Transfer functional groups
between molecules
EC 3. Hydrolases – Break bonds by adding H2O
EC 4. Lyases – Elimination reactions to form
double bonds
EC 5. Isomerases – Intramolecular rearangements
EC 6. Ligases – Join molecules with new bonds
Enzyme Nomenclature
EC 3.2.1.1
Type of general reaction Indicates specific
(eg. Hydrolase) enzyme
(eg. Alpha
Subclass of enzyme reaction Amylase)
(eg. glycosidase)
Sub-Subclass of enzyme reaction
(eg. hydrolyze O glycosyl groups)
EC 1. Oxidoreductases
➢Catalyze oxidation/reduction reactions
Oxidation is the loss of electronsor an increase in
the oxidation state of an atom, an ion, or of certain
atoms in a molecule.
Reduction is the gain of electrons or a decrease in
the oxidation state of an atom, an ion, or of certain
atoms in a molecule.
• Eg. Alcohol dehydrogenase EC 1.1.1.1.
• Cytochrome oxidase
• Amino acid oxidases
EC 2. Transferases
Involved in transfer of functional groups between
molecules
Eg. :-
➢ Hexokinase EC 2.7.1.1.
➢ Transaminases
➢ Phosphorylase
EC 3. Hydrolases
Break bonds by adding H2O
Eg:-
Lipase (triacylglycerol acyl hydrolase E.C. 3.1.1.3)
Choline esterase
Acid and alkaline phosphatase
Pepsin
Urease
EC 4. Lyases
Elimination reactions to form double bonds
Eg.-
Aldolase (E.C. 4.1.2.7)
Fumarase
Histidase
EC 5. Isomerases
Intramolecular rearangements
Eg:-
Triose phosphale isomerase EC 5.3.1.1.
Phosphohexose isomerase
EC 6. Ligases
Join molecules with new bonds
Eg:-
Glutamine synthetase EC 6.3.1.2.
Succinate thiokinase
Acetyl CoA carboxylase
