title: Dolichyl phosphate-mannosyltransferase and dolichyl phosphate-N-acetylglucosaminyltransferase activities in liver preparations from normal controls and patients with cystic fibrosis and diabetes mellitus.
abstract: Optimal assay conditions have been determined in human liver preparations for the catalytic transfer of mannose and N-acetylglucosamine from GDP-mannose and UDP-N-acetylglucosamine, respectively, to dolichyl phosphate. Both enzymatic reactions have an absolute requirement for divalent cation (5 mmol/l Mn2+ optimal), detergent (Triton X-100 or Nonidet P-40) and dolichyl phosphate (as acceptor substrate) and both reactions have optimal activity at a pH value of 7.8. Preliminary characterization of the glycolipid products for both enzymatic reactions indicates that phosphorylated dolichol is the major acceptor substrate for radiolabeled mannose and N-acetylglucosamine. The activity levels and specific activities of dolichyl phosphate-mannosyltransferase are comparable in liver homogenates from normal controls and patients with cystic fibrosis and diabetes mellitus. The activity levels and specific activities of dolichyl phosphate-N-acetylglucosaminyltransferase are comparable in liver homogenates from normal controls and patients with cystic fibrosis and diabetes mellitus but considerably lower than the activity levels of dolichyl phosphate-mannosyltransferase. It appears that two of the initial steps of the lipid-mediated glycosylation pathway are normal in livers from patients with cystic fibrosis and diabetes mellitus.
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D003550:Cystic Fibrosis / Q000201:enzymology*; D003920:Diabetes Mellitus / Q000201:enzymology*; D005964:Glucosyltransferases / Q000032:analysis*; D006602:Hexosyltransferases / Q000032:analysis*; D006801:Humans; D007223:Infant; D008099:Liver / Q000201:enzymology*; D008364:Mannosyltransferases / Q000032:analysis*; D008875:Middle Aged; D017351:N-Acetylglucosaminyltransferases
chemical_list: D005964:Glucosyltransferases; D006602:Hexosyltransferases; D008364:Mannosyltransferases; D017351:N-Acetylglucosaminyltransferases; C035783:UDP-N-acetylglucosamine-dolichyldiphosphate N-acetylglucosamine, N-acetylglucosamine transferase; C022755:dolichyl-phosphate beta-D-mannosyltransferase