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S-adenosylmethionine synthetase () (also known as methionine adenosyltransferase (MAT)) is an enzyme that creates S-adenosylmethionine (AdoMet) by reacting methionine (a non-polar amino acid) and ATP (the basic currency of energy). == Function == AdoMet is a methyl donor for transmethylation. It gives away its methyl group and is also the propylamino donor in polyamine biosynthesis. S-adenosylmethionine synthetase can be considered the rate-limiting step of the methionine cycle. S-adenosylmethionine (SAM) is a methyl donor and allows DNA methylation. Once DNA is methylated, it switches the genes off and therefore, S-adenosylmethionine can be considered to control gene expression. SAM is also involved in gene transcription, cell proliferation, and production of secondary metabolites. Hence SAM synthetase is fast becoming a drug target, in particular for the following diseases: depression, dementia, vacuolar myelopathy, liver injury, migraine, osteoarthritis, and as a potential cancer chemopreventive agent. This article discusses the protein domains that make up the SAM synthetase enzyme and how these domains contribute to its function. More specifically, this article explores the shared pseudo-3-fold symmetry that makes the domains well-adapted to their functions. This enzyme catalyses the following chemical reaction : ATP + L-methionine + H2O phosphate + diphosphate + S-adenosyl-L-methionine 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「S-adenosylmethionine synthetase enzyme」の詳細全文を読む スポンサード リンク
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