Inhibition by nojirimycin and 1-deoxynojirimycin of microsomal glucosidases from calf liver acting on the glycoprotein oligosaccharides Glc1-3Man9GlcNAc2.
Particulate membrane fractions from calf liver catalyze the release of glucose from GlcNAc2-Man9-Glc1-3-oligosaccharides. Maximal oligosaccharide-glucosidase activity was obtained at pH 6.2 and a detergent concentration of 0.5% Triton X-100. This activity could be distinguished from non-specific alpha-glucosidase activity on the basis of different pH-dependence and lack of activation by detergent. The relative rates for the hydrolysis of the Glc3-, Glc2-, and Glc1-oligosaccharide, estimated from the initial velocity, was 1:12:3. There is no significant difference in the enzyme activity towards free, peptide-bound, or lipid-linked oligosaccharide. Nojirimycin and 1-deoxynojirimycin were strong inhibitors of microsomal oligosaccharide-glucosidases. Hydrolysis of Glc3-oligosaccharide was inhibited by 50% at concentrations of 0.16 mM and 2 microM, respectively. Hydrolysis of the Glc2- and Glc1-oligosaccharide was inhibited to a somewhat lower extent, suggesting the presence of at least two glucosidases, one acting on Glc3- and one acting on Glc1- and Glc2-oligosaccharide.
D017485:1-Deoxynojirimycin / Q000031:analogs & derivatives; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002417:Cattle; D005944:Glucosamine / Q000031:analogs & derivatives / Q000494:pharmacology; D005959:Glucosidases / Q000378:metabolism*; D006023:Glycoproteins; D007700:Kinetics; D008862:Microsomes, Liver / Q000201:enzymology*; D009844:Oligosaccharides; D013379:Substrate Specificity
D000900:Anti-Bacterial Agents; D006023:Glycoproteins; D009844:Oligosaccharides; D017485:1-Deoxynojirimycin; D005959:Glucosidases; D005944:Glucosamine; C013626:nojirimycin