| Popis: |
It has generally been accepted that the production of sulfate from cysteine (or cystine) occurs through the intermediate formation of cysteinesulfinic acid (CSA) as first postulated by Pirie (1934) . The evidence for the central role of CSA has been largely based on the demonstration that various tissue preparations readily oxidize it ( Fromageot et al., 1948 ; Medes and Floyd, 1942 ; and Singer and Kearney, 1956 ). Also, CSA has been demonstrated in normal rat brain (Begeret and Chatnagner, 1954) and S35 CSA has been isolated from tissues of rats injected with S35 cysteine ( Chapeville and Fromageot, 1955 ). However, no enzyme system has been described which is capable of producing CSA from cysteine, and CSA has not been isolated in the in vitro studies of cystine oxidation to sulfate. The present study involves a system in which S35 cysteine was oxidized to S 35 O 4 = by rat liver mitochondria under conditions where added CSA remained essentially unmetabolized. Also, there was no formation of S35 CSA while S 35 O 4 = was being actively produced. The present system seems to be of quantitative importance for the matabolism of cystine in vitro . |
