Dual specificity glycosyltransferase that catalyzes the transfer of glucose and xylose from UDP-glucose and UDP-xylose, respectively, to a serine residue found in the consensus sequence of C-X-S-X-P-C (PubMed:21081508, PubMed:21490058, PubMed:21949356, PubMed:27807076, PubMed:28775322). Specifically targets extracellular EGF repeats of protein such as CRB2, F7, F9 and NOTCH2 (PubMed:21081508, PubMed:21490058, PubMed:21949356, PubMed:27807076, PubMed:28775322). Acts as a positive regulator of Notch signaling by mediating O-glucosylation of Notch, leading to regulate muscle development (PubMed:27807076). Notch glucosylation does not affect Notch ligand binding (PubMed:21490058). Required during early development to promote gastrulation: acts by mediating O-glucosylation of CRB2, which is required for CRB2 localization to the cell membrane (By similarity). L-seryl-[EGF-like domain protein] + UDP-alpha-D-xylose = 3-O-(beta-D-xylosyl)-L-seryl-[EGF-like domain protein] + H(+) + UDP L-seryl-[EGF-like domain protein] + UDP-alpha-D-glucose = 3-O-(beta-D-glucosyl)-L-seryl-[EGF-like domain protein] + H(+) + UDP Protein modification; protein glycosylation. Expressed in most adult tissues at different intensities. Abundantly expressed in liver. Expressed also in brain, heart, skeletal muscle, spleen, kidney, placenta, lung and peripheral blood leukocyte. Not detectable in colon, thymus and small intestine. Expressed in the epidermis, especially in the upper parts, stratum spinosum and stratum granulosum (at protein level). The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Belongs to the glycosyltransferase 90 family.