has part has part has role isoleucine Hile A 2-amino-3-methylpentanoic acid having either (2R,3R)- or (2S,3S)-configuration. rel-(2R,3R)-2-amino-3-methylpentanoic acid isoleucine CHEBI:24898 isoleucinate isoleucinium 2-amino-3-methylpentanoic acid sec-butyl group Daphnia magna metabolite