The major classes of enzymes

• catalyze reactions in which one molecule is oxidized while the other is reduced, transfer of electrons (e-) and hydrogens H+ • oxidases, reductases, dehydrogenases, peroxidases

• transfer carbon, nitrogen or phosphate groups • methyltransferases, aminotransferases, kinases, phosphorylases

• enzymes that catalyze a hydrolytic cleavage reaction ( transfer of functional groups to water) • nucleases, proteases, phosphatases

• catalyze the cleavage of C-C, C-S, and C-N bonds, addition of groups to double bonds, or formation of double bonds by removal of groups. • decarboxylases, aldolases, synthases

• catalyze the rearrangement of bonds within a single molecule, transfer of groups within molecules to yield isomeric forms • mutases, racemases

• Join two molecules in an energy-dependent process • Formation of C-C, C-S, C-O, and C-N bonds by condensation actions coupled to cleavage (i.e., DNA ligase joins two DNA molecules).