Type 2 hyperprolinemia: absence of delta1-pyrroline-5-carboxylic acid dehydrogenase activity

triangle up(1)-Pyrroline-5-carboxylic acid dehydrogenase activity was measured radioisotopically in normal and type 2 hyperprolinemia fibroblasts. The type 2 cells had no detectable activity over a range of reaction conditions whereas normal cells had easily measurable activity. This enzymatic defect accounts for the biochemical abnormalities in type 2 hyperprolinemia.