Journal of Biological Chemistry
Volume 275, Issue 52, 29 December 2000, Pages 40718-40724
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METABOLISM AND BIOENERGETICS
Reverse Methionine Biosynthesis fromS-Adenosylmethionine in Eukaryotic Cells*

https://doi.org/10.1074/jbc.M005967200Get rights and content
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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.

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Published, JBC Papers in Press, September 29, 2000, DOI 10.1074/jbc.M005967200

*

This work was supported by the CNRS and the Association de la Recherche sur le Cancer.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.