Abstract
Pyridoxine phosphate oxidase is probably present in aqueous extracts of E. coli. It is compared with pyridoxamine phosphate oxidase. Isoniazid and iproniazid combine with pyridoxal phosphate, but isoniazid did not combine with either pyridoxamine phosphate or pyridoxine phosphate. Both oxidase activities were partially inhibited by benzylamine and putrescine, but not by phenethylamine or cadaverine. The significance of pyridoxine phosphate oxidase in cell metabolism is discussed.