Glycoprotein biosynthesis. Rat liver microsomal glucosidases which process oligosaccharides

Asparagine-linked oligosaccharides of glycoproteins undergo extensive modification or "processing" following their attachment to protein. A key step in post-glycosylation processing is the sequential removal of glucose residues from the protein-linked oligosaccharide. We have studied rat l...

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Bibliographic Details
Published in:The Journal of biological chemistry 1979-09, Vol.254 (18), p.8814-8818
Main Authors: Grinna, L S, Robbins, P W
Format: Article
Language:English
Subjects:
Animals
Asparagine
Enzyme Activation
Glucosidases - metabolism
Glycoproteins - biosynthesis
Intracellular Membranes - drug effects
Intracellular Membranes - enzymology
Kinetics
Liver - enzymology
Male
Microsomes, Liver - drug effects
Microsomes, Liver - enzymology
Oligosaccharides - biosynthesis
Polyethylene Glycols - pharmacology
Rats
Subcellular Fractions - enzymology
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Summary:Asparagine-linked oligosaccharides of glycoproteins undergo extensive modification or "processing" following their attachment to protein. A key step in post-glycosylation processing is the sequential removal of glucose residues from the protein-linked oligosaccharide. We have studied rat liver preparations which catalyze removal of glucose from Glc3Man9GlcNAc, Glc2Man9GlcNAc, and Glc1Man9GlcNAc. Detergent solubilization studies, inhibitor studies, and temperature-activity profiles indicate that at least two distinct glucosidases are present in the membranes. One of these glucosidases removes the distal glucose from Glc3Man9GlcNAc, and the other glucosidase sequentially removes glucose from Glc2Man9GlcNAc and Glc1Man9GlcNAc. The latter glucosidase has been solubilized from the microsomal memrbranes and purified 12-fold. The glucosidases, which are integral membrane proteins, are localized in the rough and smooth microsomes and appear to be located on the cisternal surface of the microsomal vesicles. These glucosidases are suggested to be of biological importance in catalyzing the initial events in the post-glycosylation processing of cellular glycoprotein.
ISSN:0021-9258
1083-351X
DOI:10.1016/s0021-9258(19)86771-6