Reverse Methionine Biosynthesis fromS-Adenosylmethionine in Eukaryotic Cells

The intracellular ratio between methionine and its activated form S-adenosylmethionine (AdoMet) is of crucial importance for the one-carbon metabolism. AdoMet recycling into methionine was believed to be largely achieved through the methyl and the thiomethyladenosine cycles. We show here that in yea...

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Bibliographic Details
Published inThe Journal of biological chemistry Vol. 275; no. 52; pp. 40718 - 40724
Main Authors Thomas, Dominique, Becker, Aline, Surdin-Kerjan, Yolande
Format Journal Article
LanguageEnglish
Published Elsevier Inc 29.12.2000
American Society for Biochemistry and Molecular Biology
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Summary:The intracellular ratio between methionine and its activated form S-adenosylmethionine (AdoMet) is of crucial importance for the one-carbon metabolism. AdoMet recycling into methionine was believed to be largely achieved through the methyl and the thiomethyladenosine cycles. We show here that in yeast, AdoMet recycling actually occurs mainly through the direct AdoMet-dependent remethylation of homocysteine. Compelling evidences supporting this result were obtained owing to the identification and functional characterization of two new genes,SAM4 and MHT1, that encode the yeast AdoMet-homocysteine methyltransferase andS-methylmethionine-homocysteine methyltransferase, respectively. Homologs of the Sam4 and Mht1 proteins exist in other eucaryotes, indicating that such enzymes would be universal and not restricted to the bacterial or fungal kingdoms. New pathways for AdoMet or S-methylmethionine-dependent methionine synthesis are presented.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.M005967200