Inhibition of 3-mercaptopyruvate sulfurtransferase by three alpha-keto acids

Technical Report · Thu May 13 00:00:00 EDT 1993

OSTI ID:7043628

Porter, D W; Maduh, E U; Nealley, E W; Baskin, S I

3-mercaptopyruvate sulfurtransferase (3-MPST: E.C. 2.8.1.2) is an enzyme located in the cytosol and mitochondria of cells and is believed be involved in the endogenous detoxification of cyanide (CN) because it is capable of transferring sulfur from 3-mercaptopyruvate (3-MP) to CN, forming thiocyanate (SCN). In addition, 3-MPST activity is present in the erythrocyte and cyanide appears to be converted to SCN primarily in the blood, providing further evidence that 3-MPST may make a significant contribution to the endogenous detoxification of cyanide. In vitro studies of 3-MPST were designed to determine the enzymatic rate of SCN production by purified 3-MPST. 3-MPST activity was measured in 220 mM 2-amino-2-methyl-1,3-propanediol buffer (pH 9.5) with 20 mM potassium cyanide and initial 3-MP concentrations ranging from 3.3-39.5 mM (0.10-20.0 mM when corrected for cyanohydrin formation). SCN production was determined by a colorimetric assay at 460 nm. The enzyme kinetic constants were determined to be k sub (m) = 0.29 + or - 0.04 mM 3-MP and V sub (max)= 2.12 + or - 0.05 micromoles SCN/mg protein/min for 3-MPST (N=4).

• Research Organization: Army Medical Research Inst. of Chemical Defense, Aberdeen Proving Ground, MD (United States)
• OSTI ID: 7043628
• Report Number(s): AD-P-008840/1/XAB
• Country of Publication: United States
• Language: English

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