title: The effect of pyrroline-5-carboxylic acid on nucleotide metabolism in erythrocytes from normal and glucose-6-phosphate dehydrogenase-deficient subjects.
abstract: Pyrroline-5-carboxylate, the intermediate in the interconversion of proline, ornithine, and glutamate, increases 5-phosphoribosyl 1-pyrophosphate (PP-ribose-P) and purine nucleotide formation in intact human erythrocytes. We proposed that: 1) pyrroline-5-carboxylate is converted to proline by pyrroline-5-carboxylate reductase with concomitant oxidation of NADPH, 2) NADP+ augments glucose-6-phosphate dehydrogenase activity, and 3) production of ribose-5-phosphate via the pentose shunt is increased. Since glucose-6-phosphate dehydrogenase plays a central role in this proposed mechanism, we examined the responsiveness of glucose-6-phosphate dehydrogenase-deficient erythrocytes to pyrroline-5-carboxylate. We compared erythrocytes from four Sardinian glucose-6-phosphate dehydrogenase-deficient subjects and four Sardinian normal controls. Without pyrroline-5-carboxylate treatment, the levels of pentose shunt activity, PP-ribose-P, and inosine monophosphate were comparable in the two populations. However, the response to pyrroline-5-carboxylate in erythrocytes from normal and glucose-6-phosphate dehydrogenase-deficient subjects was markedly different. In normal erythrocytes, pyrroline-5-carboxylate treatment increased pentose shunt activity 600%, PP-ribose-P formation 250%, and the incorporation of hypoxanthine into inosine monophosphate 260%. In contrast, pyrroline-5-carboxylate had no effect on glucose-6-phosphate dehydrogenase-deficient erythrocytes. These findings strongly support our proposed mechanism for the pyrroline-5-carboxylate effect on nucleotides. Furthermore, the markedly different capacities for nucleotide synthesis in the two populations with pyrroline-5-carboxylate treatment suggest a role for pyrroline-5-carboxylate-mediated modulation of nucleotide metabolism in normal cells.
mesh_terms: D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D005955:Glucosephosphate Dehydrogenase Deficiency / Q000097:blood*; D006801:Humans; D007291:Inosine Monophosphate / Q000097:blood; D007700:Kinetics; D009249:NADP / Q000097:blood*; D010084:Oxidation-Reduction; D010754:Phosphoribosyl Pyrophosphate / Q000097:blood; D011685:Purine Nucleotides / Q000097:blood*; D011760:Pyrrolidinones / Q000494:pharmacology*; D011761:Pyrrolidonecarboxylic Acid / Q000494:pharmacology*; D012016:Reference Values
chemical_list: D011685:Purine Nucleotides; D011760:Pyrrolidinones; D007291:Inosine Monophosphate; D009249:NADP; D010754:Phosphoribosyl Pyrophosphate; D011761:Pyrrolidonecarboxylic Acid