CATABOLISM OF CYSTEINE, CYSTINE, CYSTEINESULFINATE, AND OTC BY ISOLATED-PERFUSED RAT HINDQUARTER

The metabolism of cysteine and related compounds was investigated in t he isolated perfused hindquarter of the rat. An erythrocyte-based perf usion medium was used; use of a perfluorochemical emulsion, FC-43, res ulted in apparent chemical oxidation of cysteine, whereas bovine eryth rocytes did not appear to contribute significantly to the metabolism o f cysteine. Rat skeletal muscle perfused with L-[S-35]cysteine, L-[S-3 5]cystine, L-[S-35]cysteinesulfinate, or L-2-oxo-[S-35]thiazolidine-4- carboxylate (OTC) for 2 h produced [S-35]sulfate and [S-35]taurine. In all cases, the partitioning of cysteine or cysteinesulfinate between metabolism to taurine and sulfate was similar, suggesting that cystein e metabolism in hindquarter may occur via formation and catabolism of cysteinesulfinate by either cysteinesulfinate decarboxylase or asparta te (cysteine-sulfinate) aminotransferase. However, the activity of cys teine dioxygenase was extremely low, suggesting that the conversion of cysteine to cysteinesulfinate may have been non-enzymatic.