GCA_000015705.1 P9303_09181 definition 2-isopropylmalate synthase GCA_000015705.1 P9303_17341 definition 3-isopropylmalate dehydrogenase GCA_000015705.1 P9303_24681 definition 3-isopropylmalate dehydratase small subunit GCA_000015705.1 P9303_24691 definition isopropylmalate isomerase large subunit