Catalyzes the liberation of alpha-xylose from the non-reducing terminal glucose of xyloglucan oligosaccharides in xyloglucan degradation, converting the 'X' to 'G' units. Hydrolysis of terminal, non-reducing alpha-D-xylose residues with release of alpha-D-xylose. kcat is 1.6 sec(-1) for Xyl-alpha-PNP. kcat is 0.071 sec(-1) for Glc-alpha-PNP. kcat is 32.6 sec(-1) for XXXG. kcat is 31.0 sec(-1) for XLLG. kcat is 1.78 sec(-1) for isoprimeverose. Optimum pH is 6.0-7.0. Glucan metabolism; xyloglucan degradation. Cell inner membrane localization is predicted by analogy with the archetypal sus locus. Severely reduced growth on tamarind xyloglucan and completely abolished growth on XyG oligosaccharides. Gut bacteria supply the human body with energy from dietary polysaccharides through glycosidases that are absent in the human genome. Xyloglucans are a ubiquitous family of highly branched plant cell wall polysaccharides present in the vegetables we consume. Enzymes involved in xyloglucan degradation mediate the conversion of otherwise indigestible plant polysaccharides to short-chain fatty acids (PubMed:24463512). Belongs to the glycosyl hydrolase 31 family.