Pyridoxine supply in human development

Vitamin B6 has an important role in the function of the human nervous system. Experimental data are not generally available on the role in human development, but significant conclusions may be made from studies of the effect of disorders of B6 vitamer metabolism. Vitamin B6 comprises seven compounds – pyridoxal, pyridoxine, pyridoxamine and their respective 5′ phosphates. The common active form in human tissue is the 5′-phosphate form of pyridoxal (PLP) most of which is found in muscle bound to phosphorylase. Like many vitamins, B6 can function both as a co-enzyme and as a chaperone. Pyridoxal-5′-phosphate is the metabolically active form and is involved in 100 enzymatic reactions including carbohydrate, amino acid, and fatty acid metabolism. There is evidence that in some situations B6 vitamers can function as antioxidants. The fetus is dependent on the placenta for supply of vitamin B6 and the demand correlates with amino acid metabolism. Few reports are available on the role of B6 in embryogenesis. Studies of human disorders where B6 metabolism is blocked show a major role in neurotransmitter function with secondary cerebral and cerebellar hypoplasia. Pyridoxine potentiates vitamin A teratogenicity and an excess leads to peripheral nerve cell degeneration. The key role of vitamin B6 in the developing human is in metabolism, especially of the neurotransmitters.