Inborn errors affecting vitamin B 6 metabolism

Abstract

Vitamin B6is an important vitamin for normal brain function. The metabolism of dietary vitamin B6to its active cofactor pyridoxal 5´-phosphate is described. The mechanism of action of pyridoxal 5´-phosphate is described, as are some important functions in the brain. The clinical features and biochemistry of three inborn errors of metabolism affecting brain pyridoxal 5´-phosphate concentrations are described, each of which cause early-onset epilepsy of variable severity. These are pyridoxine phosphate oxidase deficiency, hyperprolinemia Type 2 and pyridoxine-dependent epilepsy caused by antiquitin deficiency. Hypophosphatasia is also discussed briefly, as the epilepsy that can complicate this disorder appears to be due to pyridoxal phosphate deficiency. Lastly, the antiepileptic properties of pyridoxine and pyridoxal phosphate are discussed.