3 Disorders of GABA, Glycine, Serine, and Proline

Only for three of the knowndefects in themetabolismof the amino acidsGABA, glycine, serine, and proline has a more-or-less efficient treatment been reported: the GABA catabolic defect, succinic semialdehyde dehydrogenase deficiency (vigabatrin, causing substrate depletion by inhibition of GABA transaminase); the glycine catabolic defect, nonketotic hyperglycinemia (diet combined with benzoate and an N-methyl-d-aspartate, NMDA, receptor blocker); and 3phosphoglycerate dehydrogenase deficiency (serine supplementation, in some patients to be associated with glycine supplementation). Notreatmenthasasyetbeenattempted in∆1-pyrroline-5-carboxylate (P5CS) synthase deficiency; and the remaining six known defects probably have no clinical significance except for prolidase deficiency.