ABSTRACT
S-Adenosyl-L-methionine (SAMe) is a naturally occurring molecule present in all living organisms and present in the food chain (Table 1). SAMe is synthesized from methionine and ATP by S-adenosylmethionine synthetase (ATP-L-methionine-Sadenosyltransferase, EC 2.5.1.6) (1) and takes part in several biological reactions, either as a group donor or as an enzymatic inducer. SAMe is probably second only to ATP in the variety of reactions for which it serves as a cofactor (2). The involvement of SAMe in three important biochemical pathways-transmethylation, transsulfuration, and aminopropylation (Fig. 1)—depends on its particular structure with a positive charge on the sulfur atom, which favors the cleavage of sulfur-carbon bonds. The denomination “active methyl” for SAMe indicates the important role of this metabolite in transmethylation processes (3).
