has part has part has_part has role has role is conjugate base of is conjugate acid of imidazoles metabolite polar amino acid histidine histidina Histidine CHEBI:43118 An α-amino acid that is propanoic acid bearing an amino substituent at position 2 and a 1<em>H</em>-imidazol-4-yl group at position 3. CHEBI:5733 Histidine CHEBI:24598 DL-Histidine Histidin alpha-Amino-1H-imidazole-4-propionic acid chebi_ontology CHEBI:27570 histidinate(1-) histidinium(1+) alpha-amino acid aromatic amino acid 1H-imidazol-4-ylmethyl group