A UDP-glucose:glycoprotein glucose-1-phosphotransferase in embryonic chicken neural retina.
A subclass of cell-surface glycoproteins from embryonic chicken neural retina contains a high mannose-type oligosaccharide that terminates with glucose linked via a phosphodiester bond to penultimate mannose. This unusual oligosaccharide seems responsible for the glycoprotein attachments to the cell-surface baseplate ligatin. Using beta-32P-UDP-3H-glucose, we demonstrate in retinal homogenates the existence of a UDP-glucose:glycoprotein glucose-1-phosphotransferase (GlcPTase) that catalyzes the synthesis of such a linkage. Characterization of the doubly labeled product resulting from activity of the transferase reveals a family of endoglycosidase H-sensitive oligosaccharides displaying a cation-exchange profile similar to that of oligosaccharides derived from ligatin-associated proteins synthesized in vivo. Further analysis confirms that the incorporation of label is due to a terminal 3H-glucose joined via a 32P-phosphodiester linkage to carbon 6 of a penultimate mannose. We propose that GlcPTase may be a controlling enzyme for the targeting of certain newly synthesized proteins to the cell surface.
D000818:Animals; D002642:Chick Embryo; D007700:Kinetics; D009474:Neurons / Q000201:enzymology*; D009844:Oligosaccharides / Q000096:biosynthesis; D010761:Phosphorus Radioisotopes; D010770:Phosphotransferases / Q000378:metabolism*; D012160:Retina / Q000201:enzymology*; D013379:Substrate Specificity; D017855:Transferases (Other Substituted Phosphate Groups); D014316:Tritium; D014532:Uridine Diphosphate Glucose
D009844:Oligosaccharides; D010761:Phosphorus Radioisotopes; D014316:Tritium; D010770:Phosphotransferases; D017855:Transferases (Other Substituted Phosphate Groups); C037061:UDPglucose-glycoprotein glucose-1-phosphotransferase; D014532:Uridine Diphosphate Glucose