Classified as: (1) oxidoreductase eg dehydrogenase, oxidase, peroxidase, reductase, monoxygenase and dioxygenase; (2) transferase (transfer a group from one substrate to another) eg C1 transferase, glycosyltransferase, aminotransferase and phosphotransferase; (3) hydrolases (bond breaking using water) eg esterases, glycosidases, peptidases, amidases; (4) Lyases/Synthases (combine 2 substrates to form 1 product, no ATP needed) eg C-C lyase, C-O lyase, C-N lyase, C-S lyase; (5) Isomerases (formation of isomers similar chemical structure but different physical structure) eg epimerase, cis trans isomerase, intramolecular transferase; (6) Ligases/Synthetases (combine 2 substrates to form 1 product, ATP needed) eg C-C ligase, C-O ligase, C-N ligase, C-S ligase