Vitamins and inherited human errors of metabolism.

Vitamin therapy for inborn errors of metabolism has been used in thiamin-responsive maple syrup urine disease, homocystinuria (pyridoxine-responsive cystathionine synthetase deficiency), disorders of vitamin B12 metabolism and defective methylmalonyl-CoA mutase, biotinidase and holocarboxylase synthetase deficiency, multiple acyl-CoA dehydrogenase deficiency, defective methylene tetrahydrofolate reductase and complex III deficiency (respiratory chain). The inherited defects lead either to alterations of the apoenzymes or to deficiencies of enzymes involved in the processing or reutilization of the vitamins. The application of pharmacological doses of vitamins can be useful in these disorders in order to overcome diminished apoenzyme binding, to saturate residual activities of defective processing enzymes, to compensate for pathological losses, or for acting as electron carriers.