J. Biol. Chem., Vol. 263, Issue 10, 4527-4531, 04, 1988

S-adenosyl-L-methionine:thioether S-methyltransferase, a new enzyme in sulfur and selenium metabolism

NM Mozier, KP McConnell and JL Hoffman
Department of Biochemistry, University of Louisville, Kentucky 40292.

The final urinary excretion product of selenium detoxification is trimethylselenonium ion. An assay has been developed for the enzyme, S- adenosylmethionine:thioether S-methyltransferase, responsible for this final methylation reaction. This assay employed high pressure liquid chromatography separation and quantitation of the trimethylselenonium ion produced by thioether methyltransferase acting on S- adenosylmethionine and dimethyl selenide. The enzyme was shown to reside primarily in the cytosol of mouse lung (30 pmol/mg protein/min) and liver (7 pmol/mg protein/min). Purification from mouse lung to a preparation that exhibited a single band on sodium dodecyl sulfate- polyacrylamide gel electrophoresis was achieved by DEAE, gel filtration, and chromatofocusing chromatographies. Thioether methyltransferase is monomeric with a molecular weight of 28,000 and has a pI of 5.3. The pH optimum was 6.3, and Km values for dimethyl selenide and S-adenosylmethionine were 0.4 and 1.0 microM, respectively. The enzyme was inhibited 50% by 25 microM sinefungin, an analog of S-adenosylmethionine, or 40 microM S-adenosylhomocysteine, the reaction product. Pure thioether methyltransferase methylated selenium in dimethyl selenide, tellurium in dimethyl telluride, and S in dimethyl sulfide and many other thioethers. These data suggest a general role for this novel enzyme in the synthesis of onium compounds with increased aqueous solubility helpful in their excretion.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				M. Ding and L. A. Toth mRNA expression in mouse hypothalamus and basal forebrain during influenza infection: a novel model for sleep regulation Physiol Genomics, February 23, 2006; 24(3): 225 - 234. [Abstract] [Full Text] [PDF]

				M. Bauer, A. C. Hamm, M. Bonaus, A. Jacob, J. Jaekel, H. Schorle, M. J. Pankratz, and J. D. Katzenberger Starvation response in mouse liver shows strong correlation with life-span-prolonging processes Physiol Genomics, April 13, 2004; 17(2): 230 - 244. [Abstract] [Full Text] [PDF]

				S. Lin, Q. Shi, F. B. Nix, M. Styblo, M. A. Beck, K. M. Herbin-Davis, L. L. Hall, J. B. Simeonsson, and D. J. Thomas A Novel S-Adenosyl-L-methionine:Arsenic(III) Methyltransferase from Rat Liver Cytosol J. Biol. Chem., March 22, 2002; 277(13): 10795 - 10803. [Abstract] [Full Text] [PDF]

				B. Neuhierl, M. Thanbichler, F. Lottspeich, and A. Bock A Family of S-Methylmethionine-dependent Thiol/Selenol Methyltransferases. ROLE IN SELENIUM TOLERANCE AND EVOLUTIONARY RELATION J. Biol. Chem., February 26, 1999; 274(9): 5407 - 5414. [Abstract] [Full Text] [PDF]