Protein O-glucosyltransferase. Catalyzes the reaction that attaches glucose through an O-glycosidic linkage to a conserved serine residue found in the consensus sequence C-X-S-X-[PA]-C in epidermal growth factor-like repeats (PubMed:27428513). Regulates Notch signaling by glucosylating Notch in the ER, glucosylation is required for the correct folding and cleavage of Notch. Protein modification; protein glycosylation. Expressed both maternally and zygotically. Flies exhibit a temperature-dependent loss of Notch signaling, resulting in bristle loss (PubMed:18243100). Defects in muscle development (PubMed:27807076). Belongs to the glycosyltransferase 90 family.