has role is tautomer of homocysteine amino acid zwitterion homocysteine zwitterion 0 135.035 135.18500 2-ammonio-4-sulfanylbutanoate 2-azaniumyl-4-sulfanylbutanoate An amino acid zwitterion of homocysteine arising from transfer of a proton from the carboxy to the amino group; major species at pH 7.3. C4H9NO2S CHEBI:58065 FFFHZYDWPBMWHY-UHFFFAOYSA-N InChI=1S/C4H9NO2S/c5-3(1-2-8)4(6)7/h3,8H,1-2,5H2,(H,6,7) [NH3+]C(CCS)C([O-])=O chebi_ontology Saccharomyces cerevisiae metabolite Escherichia coli metabolite human metabolite