Evidence for multiple enzymes in the dolichol utilizing pathway of glycoprotein biosynthesis.
A comparison has been made of the enzymes catalyzing the transfer of mannose, glucose and N-acetylglucosamine from, respectively, GDPmannose, UDP-glucose and UDP-N-acetylglucosamine to endogenous dolichol phosphate (Dol-P) in liver Golgi membranes. Evidence is presented with suggests that all three reactions utilize the same pool of Dol-P. The transfer of mannose from GDP-Man to Dol-P is not inhibited by 0.1 mM UDP or UMP; 0.1 mM GDP did block the accumulation of mannose in Dol-P-Man. The net transfer of glucose and N-acetylglucosamine to Dol-P is prevented by 0.1 mM UDP but not 0.1 mM GDP. UDPglucose inhibits the reverse of the glucose transfer reaction but not the reverse of the N-acetylglucosamine or mannose trasfer reaction. On the basis of this, and other data, it is concluded that the three sugar transfer reactions utilize separate enzymes.
D000818:Animals; D002417:Cattle; D004224:Diterpenes / Q000378:metabolism*; D004286:Dolichols / Q000378:metabolism*; D005964:Glucosyltransferases / Q000378:metabolism; D006023:Glycoproteins / Q000096:biosynthesis*; D006602:Hexosyltransferases / Q000378:metabolism; D066298:In Vitro Techniques; D008099:Liver / Q000201:enzymology*; D008364:Mannosyltransferases / Q000378:metabolism; D008566:Membranes / Q000201:enzymology
D004224:Diterpenes; D004286:Dolichols; D006023:Glycoproteins; D005964:Glucosyltransferases; D006602:Hexosyltransferases; D008364:Mannosyltransferases