Pyrroline-5-carboxylate reductase in human erythrocytes.

Abstract

Pyrroline-5-carboxylate reductase, which converts pyrroline-5-carboxylate to proline, has been identified in human erythrocytes. The level of pyrroline-5-carboxylate reductase activity in these cells is comparable to the activity levels ofmajor erythrocyte enzymes. The physiologic function of the enzyme in erythrocytes cannot be related to its function in other tissues, i.e., producing proline for protein synthesis. We examined the kinetic properties of erythrocyte pyrroline-5-carboxylate reductase and compared them to the properties of the enzyme from proliferating cul- tured human fibroblasts. We found that the kinetic properties and regulation ofthe erythrocyte enzyme are distinctly different from those for human fibroblast pyr- roline-5-carboxylate reductase. These characteristics are consistent with the interpretation that the function of the enzyme in human erythrocytes may be to gen- erate oxidizing potential in the form of NADP+.