PMID:3818665

Citation	Lubas, WA and Spiro, RG (1987) Golgi endo-alpha-D-mannosidase from rat liver, a novel N-linked carbohydrate unit processing enzyme. J. Biol. Chem. 262:3775-81
Abstract	An enzyme has been found in Triton-treated rat liver Golgi membranes which trims Glc1Man9GlcNAc to Man8GlcNAc with the release of Glc alpha 1-3Man. By removing a glucosylmannose disaccharide and yielding only one Man8GlcNAc isomer, this endo-alpha-D-mannosidase provides a processing route alternative to the sequential actions of alpha-glucosidase II and alpha-mannosidase I. The endomannosidase was fully active in the presence of 1-deoxynojirimycin and EDTA which inhibited exoglycosidase release of glucose and mannose, respectively, and these agents were, therefore, included in the standard assay. The specific activity of the endomannosidase was found to be 69-fold greater in Golgi than in rough endoplasmic reticulum (RER) membranes, and Golgi-RER mixing experiments excluded the possibility that the low activity in the RER was the result of some inhibitor present in this fraction. The neutral pH optimum (approximately 7.0) of the enzyme was consistent with a role in N-linked oligosaccharide processing. The existence of an endo-alpha-D-mannosidase pathway for glucose removal could provide an explanation for the incomplete block in oligosaccharide processing which is observed in cells with inhibited or deficient alpha-glucosidase.
Links	PubMed
Keywords	Animals; Golgi Apparatus/enzymology; Intracellular Membranes/enzymology; Kinetics; Liver/enzymology; Male; Mannosidases/metabolism; Oligosaccharides/metabolism; Protein Processing, Post-Translational; Rats
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
RAT:MANEA		GO:0000139: Golgi membrane	ECO:0000314:		C		FIG. 8. Comparison of endomannosidase activity in Golgi, RER, and total microsomal (Micro) fractions from rat liver.	complete

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