title: Yeast, plants, worms, and flies use a methyltransferase to metabolize age-damaged (R,S)-AdoMet, but what do mammals do?
abstract: The biological methyl donor S-adenosyl-L-methionine [(S,S)-AdoMet] can spontaneously break down under physiological conditions to form the inactive diastereomer (R,S)-AdoMet, which may interfere with cell function. Although several lower organisms metabolize (R,S)-AdoMet via homocysteine methyltransferases, it is unclear how mammals deal with it. In this paper, we show that the mouse liver extracts, containing the BHMT-2 homocysteine methyltransferase candidate for a similar activity, recognizes (S,S)-AdoMet but not (R,S)-AdoMet. We find no evidence for the enzymatic breakdown of (R,S)-AdoMet in these extracts. Thus, mammals may metabolize (R,S)-AdoMet using a different strategy than other organisms.
authors.affiliation: Department of Chemistry and Biochemistry , Molecular Biology Institute, University of California , Los Angeles, Los Angeles, California 90095-1569, USA.
authors.forename: Chris R
authors.initials: CR
authors.lastname: Vinci
authors.forename: Steven G
authors.initials: SG
authors.lastname: Clarke
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D050940:Betaine-Homocysteine S-Methyltransferase / Q000378:metabolism / Q000502:physiology; D002384:Catalysis; D004175:Diptera / Q000235:genetics / Q000378:metabolism; D006376:Helminths / Q000235:genetics / Q000378:metabolism; D050904:Homocysteine S-Methyltransferase / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D008099:Liver / Q000201:enzymology / Q000378:metabolism; D008322:Mammals / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008968:Molecular Conformation; D018384:Oxidative Stress; D010944:Plants / Q000235:genetics / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000737:chemistry / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism / Q000502:physiology; D013379:Substrate Specificity; D015003:Yeasts / Q000235:genetics / Q000378:metabolism
chemical_list: C494552:Bhmt2 protein, mouse; D029701:Saccharomyces cerevisiae Proteins; D012436:S-Adenosylmethionine; D050904:Homocysteine S-Methyltransferase; C519167:MHT1 protein, S cerevisiae; C519166:SAM4 protein, S cerevisiae; D050940:Betaine-Homocysteine S-Methyltransferase