Formation of sulfate from L-cysteine in rat liver mitochondria

Formation of sulfate in rat liver mitochondria was studied. About 0.1 μmol of sulfate was formed in mitochondria from 1g of liver in 60min when 10mM L-cysteine was used as the substrate. Addition of either 10mM 2-oxoglutarate or 10mM glutathione to this system increased sulfate formation 3 to 4 times. The addition of both 2-oxoglutarate and glutathione resulted in a 20-fold increase in sulfate formation. Sulfate formation in the presence of 5mM L-cysteine was 58% of that with 10mM L-cysteine. L-Cysteine-glutathione mixed disulfide was not a good substrate, indicating that this mixed disulfide was not an intermediate of sulfate formation in the present system. Incubation of 3-mercaptopyruvate with rat liver mitochondria also resulted in sulfate formation, and the addition of glutathione accelerated it. Formation of sulfite and thiosulfate was also detected. These results indicate that sulfate is produced in mitochondria, at least in part, from L-cysteine through the transamination pathway (3-mercaptopyruvate pathway).