ENZYME NOMENCLATURE

• Derived from substrate or chemical reaction the enzyme catalyzes
• Most enzyme names have suffix “–ase”

Isozymes (isoenzymes)

• Enzymes that catalyze same reaction but have different amino acid sequences (different proteins)

ENZYMES REQUIRING COFACTORS

Apoenzyme

• Enzyme without the cofactor.

Holoenzyme

• Enzyme and cofactor together

6 CLASSES OF ENZYMES

Oxidoreductases

• Catalyze electron transfer reactions (oxidation/reduction reactions)
• A- + B → A + B-

Transferases

• Catalyze transfer of functional groups to a molecule
• A-B + PO4 → A-B-PO4

Hydrolases

• Catalyze breakage of bonds by hydrolysis (addition of water)
• A-B-C + H2O → A-B + C

Lyases

• Catalyze bond cleavage reactions that are not oxidation or hydrolysis reactions
• A-B-C → A-B + C

Isomerases

• Catalyze rearrangement reactions
• A-B-C → A-C-B

Ligases

• Catalyze reactions in which covalent bonds join two molecules
• A-D + B-C→ A-D-B-C