BIOCHEMICAL MECHANISMS IN METHYL GROUP TRANSFER

Abstract

This chapter presents an overview of biochemical mechanisms in methyl group transfer. The transfer of the methyl group may be regarded as a special case of a group transfer reaction. The group transferred—the methyl moiety—is among the simplest of organic structures. The presence of methylated compounds in natural sources has been known for more than a century. Since Dessaignes demonstrated the presence of a methyl group in creatine, the list of naturally occurring compounds containing a methyl group attached to nitrogen, sulfur, oxygen, or other atoms has increased extensively to include a very large number of substances. The presence of such methylated compounds in natural sources has been established for long. In recent years, the technique of mass spectrometry has been utilized to establish further instances of biological transfer of the intact methyl group. In the chapter, the biochemistry of methyl group transfer is reviewed with emphasis on chemical and enzymic mechanisms. The chapter also discusses methylation of homocysteine and methionine biosynthesis and describes energetics of transmethylation .