The enzymes are classified into 6 groups on the basis of type of reaction they catalyze.
Reaction Catalyzed: Transfer of H and O atoms or electrons from one substance to another.
Examples: Dehydrogenase, Oxidase
Reaction Catalyzed: Transfer of a specific group from one substance to another.
Examples: Kinase, Transaminase
Reaction Catalyzed: Hydrolysis of a substance.
Examples: Lipase, Amylase, Peptidase, Esterase, Phosphatase, Protease, Carbohydrase
Reaction Catalyzed: non hydrolytic removal or addition of group substrates. C-C, C-N, C-O or C-S bonds may be spilt.
Examples: Fumarase, Aldolase, Decarboxylase
Reaction Catalyzed: Change of a substrate into a related form by intramolecular rearrangement
Reaction Catalyzed: Joining of two molecules by synthesis of new C-O, C-S, C-N or C-C bonds with simultaneous breakdown of ATP.
Examples: Pyruvate carboxylase, Acetyl CoA synthases