In 1961, the International Union of Biochemistry (IUB) appointed an Enzyme Commission which classified enzymes into six different groups/classes. Each class represents the general reaction brought about by the enzymes of that class.
Enzymes are classified into six classes:
|
Enzyme Class
|
Reaction catalyzed
|
Equation
|
Examples
|
|
Oxidoreductases
|
Oxidation-Reduction
|
XH2 + Y ―→
X + YH2
|
Alcohol dehydrogenase, Cytochrome oxidase
|
|
Transferase
|
Group Transfer
|
C—X + D―→
C + D —X
|
Transaminase, Transpeptidase, Hexokinase
|
|
Hydrolase
|
Hydrolysis
|
X—Y + H2O―→
XH + YOH
|
Protease, Lipase, Amylase, Esterase, Pepsin
|
|
Lyases
|
Addition-Elimination
|
A—B + X—Y―→
AX + BY
|
Aminase, Aldolase, Fumarase, Carboxylase
|
|
Isomerase
|
Inter-conversion of isomers
|
B―→B’
|
Racemase, Phosphohexose isomerase
|
|
Ligases
|
Condensation (usually ATP dependent)
|
X + Y―→
X—Y
(ATP ―→ ADP + iP)
|
Succinate thiokinase, Tryptophan synthetase
|
