has role 1-methylhistidine zwitterion An alpha-amino acid zwitterion obtained by transfer of a proton from the carboxy to the amino group of 1-methylhistidine; major species at pH 7.3. 2-azaniumyl-3-(1-methyl-1H-imidazol-4-yl)propanoate CHEBI:133608 1-methylhistidine alpha-amino-acid zwitterion human urinary metabolite