Abstract The proteins encoded in the yicI and yihQ gene of Escherichia coli have similarities in the amino acid sequences to glycoside hydrolase family 31 enzymes, but they have not been detected as the active enzymes. The functions of the two proteins have been first clarified in this study. Recombinant YicI and YihQ produced in E. coli were purified and characterized. YicI has the activity of α-xylosidase. YicI existing as a hexamer shows optimal pH at 7.0 and is stable in the pH range of 4.7–10.1 with incubation for 24 h at 4 °C and also is stable up to 47 °C with incubation for 15 min. The enzyme shows higher activity against α-xylosyl fluoride, isoprimeverose (6- O-α-xylopyranosyl-glucopyranose), and α-xyloside in xyloglucan oligosaccharides. The α-xylosidase catalyzes the transfer of α-xylosyl residue from α-xyloside to xylose, glucose, mannose, fructose, maltose, isomaltose, nigerose, kojibiose, sucrose, and trehalose. YihQ exhibits the hydrolysis activity against α-glucosyl fluoride, and so is an α-glucosidase, although the natural substrates, such as α-glucobioses, are scarcely hydrolyzed. α-Glucosidase has been found for the first time in E. coli.