Abstract
We have studied the transamination pathway (3-mercaptopyruvate pathway) of l-cysteine metabolism in rats. Characterization of cysteine aminotransferase (EC 2.6.1.3) from liver indicated that the transamination, the first reaction of this pathway, was catalyzed by aspartate aminotransferase (EC 2.6.1.1). 3-Mercaptopyruvate, the product of the transamination, may be metabolized through two routes. The initial reactions of these routes are reduction and transsulfuration, and the final metabolites are 3-mercaptolactate-cysteine mixed disulfide [S-(2-hydroxy-2-carboxyethylthio)cysteine, HCETC] and inorganic sulfate, respectively. The study using anti-lactate dehydrogenase antiserum proved that the enzyme catalyzing the reduction of 3-mercaptopyruvate was lactate dehydrogenase (EC 1.1.1.27). Formation of HCETC was shown to depend on low 3-mercaptopyruvate sulfurtransferase (EC 2.8.1.2) activity. Results were discussed in relation to HCETC excretion in normal human subjects and patients with 3-mercaptolactate-cysteine disulfiduria. Incubation of liver mitochondria with l-cysteine, 2-oxoglutarate and glutathione resulted in the formation of sulfate and thiosulfate, indicating that thiosulfate was formed by transsulfuration of 3-mercaptopyruvate and finally metabolized to sulfate.
Original language | English |
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Pages (from-to) | 243-252 |
Number of pages | 10 |
Journal | Amino Acids |
Volume | 3 |
Issue number | 3 |
DOIs | |
Publication status | Published - Oct 1 1992 |
Keywords
- 3-Mercaptolactate-cysteine mixed disulfide
- 3-Mercaptopyruvate pathway
- Amino acids
- Cysteine metabolism
- Cysteine transamination
- Sulfate formation
ASJC Scopus subject areas
- Biochemistry
- Clinical Biochemistry
- Organic Chemistry