Pyridoxine-5’-phosphate oxidase(PNPO) is the rate-limiting enzyme in vitamin B6 synthesis. Vitamin B6(Pyridoxal 5-prime-phosphate or PLP) is vital for normal cellular function, and some cancer cells have notable differences in vitamin B6 metabolism compared to their normal counterparts.Vitamin B6 is an essential co-factor for enzymes involved in both homocysteine metabolism and synthesis of neurotransmitters such as catecholamine. Mutations in the PNPO gene result in PNPO deficiency, a form of neonatal epileptic encephalopathy.