title: Cations in component reactions of 'malic' enzyme catalysis.
abstract: The ;malic' enzyme (EC 1.1.1.40) has been purified (300-fold) from wheat germ and its abilities to catalyse the decarboxylation and the hydrogenation of oxaloacetic acid and oxaloacetate esters was studied. The free 1-carboxyl group is essential for the interaction of oxaloacetates and substituted oxaloacetates with the enzyme via cations. The free 4-carboxyl group is required for the decarboxylation but is not indispensable for the hydrogenation. At high concentrations, cations inhibit the enzymic hydrogenation of oxaloacetic acid but not that of 4-ethyl oxaloacetate. A plausible inhibitory mechanism is proposed.
mesh_terms: D002384:Catalysis; D002625:Chemistry, Organic; D003653:Decarboxylation; D006865:Hydrogenation; D008291:Malate Dehydrogenase; D008345:Manganese; D009249:NADP; D055601:Organic Chemistry Phenomena; D010071:Oxaloacetates
chemical_list: D010071:Oxaloacetates; D008345:Manganese; D009249:NADP; D008291:Malate Dehydrogenase