Enzymatic N-Methylation of Histamine

Abstract

THE in vivo studies of Schayer¹ have shown ring N-methylation to be the principal pathway of histamine metabolism in a variety of mammalian species. His work demonstrates the following scheme: Kobayashi² found that incubation of histamine with whole-liver homogenates resulted in the formation of 1-methylimidazole-4-acetic acid. These observations reflect the summation of at least three enzymatic processes, one of which is concerned with the synthesis of a co-factor needed for histamine methylation. This report describes the isolation and properties of an enzyme, imidazole N-methyl transferase, which catalyses the ring-N-methylation of histamine requiring S-adenosylmethionine as the methyl donor.