carnosine amino-acid zwitterion carnosine zwitterion carnosine CHEBI:57485 (2S)-2-[(3-azaniumylpropanoyl)amino]-3-(1H-imidazol-4-yl)propanoate MetaCyc:CARNOSINE N(alpha)-(beta-alaniniumyl)-L-histidinate Zwitterionic form of carnosine. carnosinate