Formation and excretion of pyrrole-2-carboxylic acid. Whole animal and enzyme studies in the rat.
A corrected method for the measurement of pyrrole-2-carboxylate in rat urine was used in studies of its excretion under various experimental conditions. The findings implicated administered hydroxy-L-proline as a relatively efficient source of urinary pyrrole-2-carboxylate and tended to exclude administered L-proline as a significant direct source. Removal of aerobic gut flora had no influence on the excretion of pyrrole-2-carboxylate either endogenously or following hydroxy-L-proline administration. Related studied showed that rat kidney L-amino acid oxidase catalyzes oxidation of hydroxy-L-proline to delta1-pyrroline-4-hydroxy-2-carboxylate, which is converted to pyrrole-2-carboxylate on acidification of reaction mixtures. All findings were consistent with hydroxy-L-proline as the source of endogenous pyrrole-2-carboxylate excretion. Excretion patterns and labeling patterns were compared after administration of pyrrole-2-carboxylate or of hydroxy-proline epimers. From these data, the true excretion product of hydroxy-L-proline oxidation by L-amino acid oxidase appeared to be the unstable oxidation product, delta1-pyrroline-4-hydroxy-2-carboxylate, which is converted to pyrrole-2-carboxylate in urine. The capacity of homogenates of guinea pig kidney and human kidney to carry out oxidation of hydroxy-L-proline to pyrrole-2-carboxylate was much less than that of rat kidney, consistent with the lower levels of urinary pyrrole-2-carboxylate in these species. Experiments designed to examine the modest increase of pyrrole-2-carboxylate excretion after proline loads led to new observations on tissue levels of hydroxy-L-proline following proline administration and on the inhibition by L-proline of hydroxy-L-proline oxidase.
D000429:Alcohol Oxidoreductases / Q000378:metabolism; D000594:Amino Acid Oxidoreductases / Q000302:isolation & purification / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D002264:Carboxylic Acids / Q000378:metabolism* / Q000652:urine; D002374:Catalase; D002417:Cattle; D002852:Chromatography, Ion Exchange; D003605:D-Amino-Acid Oxidase / Q000378:metabolism; D006168:Guinea Pigs; D006801:Humans; D006909:Hydroxyproline / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D007700:Kinetics; D007930:Leucine / Q000378:metabolism; D008099:Liver / Q000201:enzymology; D011392:Proline / Q000378:metabolism; D011758:Pyrroles / Q000378:metabolism* / Q000652:urine; D051381:Rats; D013552:Swine
D000596:Amino Acids; D002264:Carboxylic Acids; D011758:Pyrroles; D011392:Proline; D000429:Alcohol Oxidoreductases; D002374:Catalase; D000594:Amino Acid Oxidoreductases; D003605:D-Amino-Acid Oxidase; D007930:Leucine; D006909:Hydroxyproline