Disorders of Proline and Serine Metabolism

Four disorders of proline metabolism are known: two in its catabolism (hyperprolinaemia type I, which is due to proline oxidase deficiency, and hyperprolinaemia type II, which is due to ∆-pyrroline 5-carboxylate dehydrogenase deficiency) and two in its synthesis (∆1-pyrroline 5-carboxylate synthase deficiency and ∆-pyrroline 5-carboxylate reductase deficiency). Hyperprolinaemia type I is generally considered a nondisease, while hyperprolinaemia type II appears to be associated with a disposition to recurrent seizures. The deficiency of the proline-synthesising enzyme, ∆-pyrroline 5-carboxylate synthase, which is also involved in ornithine synthesis, is described in ► Chapter 22.