S-adenosylmethionine is an activated methionine derivative in which an adenosyl group is bonded to the sulfur atom. The positively charged sulfur bears a transferable methyl group; S-adenosylmethionine therefore couples cellular metabolism to transfer of methyl groups onto other molecules, including DNA and proteins.[ref]
PubChem Compound database by National Center for Biotechnology Information. S-adenosylmethionine records CID34755 and parent CID34756; structure, charge conventions and methyl-donor role
The same starting molecule can also enter a different reaction. 1-aminocyclopropane-1-carboxylate synthase converts S-adenosylmethionine into 1-aminocyclopropane-1-carboxylate and methylthioadenosine, on the route to plant Ethylene. Here the enzyme directs fragmentation and ring formation rather than simple methyl group transfer. Naming a common substrate does not by itself identify which reaction occurred.[ref]
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