MOD_OGLYCOS

O-Glucose is an unusual form of post-translational modification consisting of glucose directly attached to protein through O-linkage to a serine residue. Several serum proteins contain this unique modification on their epidermal growth factor (EGF)-like repeats. The enzymatic activity capable of adding glucose to EGF repeats is UDP-glucose:protein O-glucosyltransferase. The glucose is added in O-linkage to the EGF repeat. The two cysteines of the motif are the first and second of the six conserved cysteines of the EGF repeat. The enzyme recognizes not only the consensus sequence but also the 3D structure of the EGF repeat. O-glucosyltransferase activity has been detected in extracts of cell lines from insects to humans and a variety of rat tissues. Numerous secreted and cell surface proteins are predicted to bear O-glucose.