S-Adenosylmethionine and its sulfur metabolites

This chapter discusses the S-adenosylmethionine and its sulfur metabolites. Biological reactions in which S-adenosylmethionine (AdoMet) is the methyl donor are key processes in many diverse cellular functions, such as transmethylation, transsulfuration, and polyamine biosynthesis. Some of the key metabolites of AdoMet are S-adenosylhomocysteine (AdoHcy), decarboxylated S-adenosylmethionine (dcAdoMet), and methylthioadenosine (MeSAdo). The use of specific inhibitors of S- adenosylhomocysteine hydrolase results in the accumulation of AdoHcy and subsequent inhibition of trans-methylation reactions, and a variety of biological and biochemical perturbations have been attributed to an increase in the ratio of AdoHcy (or S-nucleosidylhomocysteine) to AdoMet. Of particular interest are antiviral effects, modulation of cellular differentiation, and immunological effects. The chapter describes a high-performance liquid chromatographic (HPLC) procedure that quantitatively separates most of the AdoMet metabolites, including S-inosylhomocysteine (lnoHcy) and S-adenosyl-cysteine (AdoCys), and also detects the formation of novel AdoMet analogs. There are two HPLC procedures that can be used. The first (Method A) requires more time but separates more sulfur metabolites; the second (Method B) is shorter for routine use in the assay of AdoHcy and AdoMet.