Activation of pyridoxamine 5'-phosphate oxidase by aliphatic primary amine

The reason for observed variable activities of yeast pyridoxaminephosphate oxidase (EC 1.4.3.5; deaminating) was studied. In the presence of an aliphatic primary amine, the pyridoxamine 5'-phosphate oxidase activity was elevated up to 5-fold, whereas pyridoxine 5'-phosphate oxidase was unchanged. Activation resulted from an enhanced Vmax with an almost constant Km. Polyamines (spermine greater than spermidine greater than putrescine) were excellent activators. On the contrary, oxidation of pyridoxine 5'-phosphate or synthetic N-(5'-phospho-4-pyridoxyl)-amino acid was not activated so much. However, a decrease in Km was observed with the increase in the putrescine concentrations.