0-Mercaptopyruvate

Duo S, Lea TC, Stipanuk MH. 1983. Developmental pattern, tissue distribution, and subcellular distribution of cysteine -ketoglutarate aminotransferase and 3-mercaptopyruvate sulfurtransferase activities in the rat. Biol Neonat 43 23-32. 

Wing DA, Patel HC, Baskin SI. 1992. The effect of picrylsulphonic acid on in vitro conversion of cyanide to thiocyanate by 3-mercaptopyruvate sulphurtransferase and rhodanese. Toxicol In Vitro 6(6) 597-603. 

This zinc-dependent enzyme [EC 2.8.1.2] catalyzes the reaction of 3-mercaptopyruvate with cyanide to produce pyruvate and thiocyanate. Other substrates include sulfite, sulfinates, mercaptoethanol, and mercaptopyruvate. 

Mercaptopyruvate, Thiosulfate, and Assembly of Iron-Sulfur Centers... 

An important property of 3-mercaptopyruvate arises from electron withdrawal by the carbonyl group. This makes the SH group electrophilic and able to be transferred as SH+, S°, to a variety of nucleophiles (Eq. 24-44). Thus sulfite yields thiosulfate (S2032 + H+, Eq. 24-45, step a), cyanide yields thiocyanate (Eq. 24-45, step b), and cysteine sulfinate yields alanine thiosulfonate.448 461 The reactions are catalyzed by mercaptopyruvate sulfurtransferase, an enzyme very similar to thiosulfate sulfurtransferase. The latter is a liver enzyme often called by the traditional... 

Hydrogen cyanide is metabolized through several pathways. In the major metabolic pathway (60-80% of absorbed cyanide), cyanide is converted to thiocyanate in a reaction that is catalyzed by rhodanase or 3-mercaptopyruvate sulfur transferase (Baumann et al. 1934 Himwich and Saunders 1948 Wood and Cooley 1956 Singh et al. 1989). Minor pathways include the oxidation of hydrogen cyanide or thiocyanate to carbon dioxide, reaction with cystine to form 2-aminothiazoline-4-carboxylic acid and 2-imnothizolidine-4-carboxylic acid, reaction with hydroxocobalamine to form cyanocobalamin, and conversion of hydrogen cyanide to formic acid, which enters one-carbon metabolism in the body (Wood and Cooley 1956 Boxer and Rickards 1952 Ansell and Lewis 1970 Baumeister et al. 1975). 

Okoh and Pitt, 1982 Silver et al., 1982). Thus, rat LD50 values for NaCN by the peroral (po) and intraperitoneal (ip) routes are respectively 5.7 and 4.72 mg kg-1, and the corresponding values for NaSCN are 764 and 540 mg kg-1 thus, the conversion of NaCN to NaSCN results in a decrease in acute lethal toxicity by a factor of about 120-fold in the rat (Ballantyne, 1984). SCN is renally excreted with a half-life of 2.7 days in healthy subjects (Schulz et al., 1983). Two enzyme systems are responsible for the transulphuration process (Ballantyne, 1987b Lang, 1933 Sorbo, 1975) thiosulphate-cyanide transulphurase (EC 2.8.1.1 rhodanese) and (3-mercaptopyruvate-cyanide transulphurase (EC 2.8.1.2). Thiosulphate-cyanide transulphurase is a mitochondrial enzyme that catalyzes the transfer of a sulphane sulphur atom from sulphur donors to sulphur acceptors ... 

Another catabolic pathway is transamination (Fig. 24-25, rection h) to 3-mercaptopyravate. The latter compound can be reductively cleaved to pyruvate and sulfide. Cysfeine can also be oxidized by NAD and lacfafe dehydrogenase to 3-mercaptopyruvate. An interesting PLP-dependent p-replacement reaction of cysfeine leads to P-cyanoalanine, the lathyritic factor (Box 8-E) present in some plants. This reaction also detoxifies the HCN produced during the biosynthesis of ethylene from ACC. 

Jarabak R, Westley J. Steady-state kinetics of 3-mercaptopyruvate sulfurtransferase from bovine kidney. Arch Biochem Biophys. 1978 185 458-465. 

Porter DW, Baskin SI. The effect of three a-keto acids on 3-mercaptopyruvate sulfurtransferase activity. J Biochem Toxicol. 1996 11 45-50. 

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