YihQ is a bacterial alpha-glucosidase with a conserved glycosyl hydrolase family 31 (GH31) domain that catalyzes the release of an alpha-glucosyl residue from the non-reducing end of alpha-glucoside substrates such as alpha-glucosyl fluoride. Orthologs of YihQ that have not yet been functionally characterized are present in plants and fungi. YihQ has sequence similarity to other GH31 enzymes such as CtsZ, a 6-alpha-glucosyltransferase from Bacillus globisporus, and YicI, an alpha-xylosidase from Echerichia coli. These latter two belong to different GH31 subfamilies than YihQ. In bacteria, YihQ (along with YihO) is important for bacterial O-antigen capsule assembly and translocation.
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