The Enzymatic α-N-Methylation of Histidine

Cell-free extracts of Neurospora crassa catalyze the methylation of the α-amino nitrogen atom of histidine, α- N -methylhistidine, and α- N,N -dimethylhistidine to form hercynine (α- N,N,N -trimethylhistidine). S -Adenosylmethionine serves as the common methyl group donor. The enzyme system responsible for these methylations has been purified 500-fold by DEAE-cellulose chromatography, ammonium sulfate fractionation, gel filtration, and DEAE-Sephadex chromatography. The most highly purified preparation showed a single major component during acrylamide gel electrophoresis. Fractionation studies, kinetic studies, inhibition studies, and heat-inactivation studies all indicate that a single enzyme (histidine-α- N -methyltransferase) is responsible for the three transmethylation reactions involved in the conversion of histidine to hercynine.