PRODH and schizophrenia: Peripheral hyperprolinemia, which reflects CNS proline elevation,4, 5, 6, 7, 8, 9 has been associated with psychiatric disorders including schizophrenia.10, 11, 12 The proline dehydrogenase gene (PRODH) encodes proline oxidase (POX), the enzyme that catalyzes the first step in proline catabolism.