The glutathione dependence of inorganic sulfate formation from l- or d-cysteine in isolated rat hepatocytes |
| |
Authors: | James Huang Sumsullah Khan Peter J O’Brien |
| |
Institution: | James Huang, Sumsullah Khan,Peter J. O’Brien |
| |
Abstract: | The GSH dependence of the metabolic pathways involved in the conversion of cysteine to sulfate in intact cells has been investigated. It was found that hepatocyte-catalysed sulfate formation from added -cysteine did not occur if hepatocyte GSH was depleted beforehand, but was restored when GSH levels recovered. Furthermore, sulfate formation did not recover in GSH-depleted hepatocytes if GSH synthesis was prevented with buthionine sulfoximine. Thiosulfate formation was, however, markedly enhanced in GSH-depleted hepatocytes. These results suggest that thiosulfate is an intermediate in the formation of inorganic sulfate from -cysteine and that GSH was required for the conversion of thiosulfate to inorganic sulfate. Much less sulfate was formed if the cysteine was replaced with cysteinesulfinate. Furthermore, sulfate formation from -cysteine was markedly inhibited by the addition of the transaminase inhibitor -cycloserine or the γ-cystathionase inhibitor -propargylglycine. The major routes of sulfate formation from -cysteine therefore seems to involve pathways that do not involve -cysteinesulfinate. Similar amounts of sulfate were formed from -cysteine as -cysteine. Thiosulfate instead of sulfate was also formed in GSH-depleted hepatocytes. However, sulfate formation from -cysteine differed from -cysteine in that it was inhibited by the -aminoacid oxidase inhibitor sodium benzoate and was not affected by transaminase or γ-cystathionase inhibitors. These results suggest that thiosulfate is an intermediate in sulfate formation from -cysteine and involves the oxidation of -cysteine by -amino acid oxidase to form β-mercaptopyruvate. |
| |
Keywords: | cell isolation protein metabolism glutathione thiosulfate |
本文献已被 ScienceDirect 等数据库收录! |
|