Enzymatic Synthesis of Anserine in Skeletal Muscle by N-Methylation of Carnosines

Anserine biosynthesis may occur in skeletal muscle by two and possibly three pathways: (a) condensation of l-methylhistidine with p-alanine (1, Z), (6) direct N-methylation of carnosine (3, 4), and, possibly, (c) P-alanyl transfer from carnosine to 1-methylhistidine (5). The relative importance of these various routes is unevaluated, although some studies in viva suggest that species differences are significant, e.g. methionine but not l-methylhistidine is utilized for the synthesis in viva of anserine in the rat, in contrast to the chick which can utilize either compound (7, 8). Winnick and Winnick (3) have shown that S-adenosyl-nmethionine may function as a methyl donor for the synthesis in vitro of anserine and to a lesser degree for synthesis of lmethylhistidine. The present paper describes a further investigation of the properties and specificity of the enzyme obtained from chick muscle, carnosine-N-methyl transferase, which catalyses the synthesis of ‘anserine by transfer of the methyl group of S-adenosylmethionine to carnosine. A preliminary report of this work has appeared (4).