pyridoxine 5′-phosphate oxidase is an enzyme that catalyzes several reactions in the vitamin b metabolism pathway. pyridoxine 5′-phosphate oxidase catalyzes the final, rate-limiting step in vitamin b metabolism, the biosynthesis of pyridoxal 5′-phosphate, the biologically active form of vitamin b which acts as an essential cofactor. pyridoxine 5′-phosphate oxidase is a member of the enzyme class oxidases, or more specifically, oxidoreductases. these enzymes catalyze a simultaneous oxidation-reduction reaction. the substrate oxidase enzymes is hydroxlyated by one oxygen atom of molecular oxygen.