Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.1.52 (PNGase F)
 1,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Because of the limited information available about the synthesis of N-linked glycoproteins in nerve cells, in regard to both processing steps and enzyme characterization, the biosynthetic processing of Thy-1 of the rat neuronal tumor cell line BN-1010-1 has been investigated using several inhibitors of biosynthesis and transport. (i) Tunicamycin completely inhibited mannose incorporation into Thy-1. Unglycosylated Thy-1 was not transported to the cell surface and was probably degraded rapidly following synthesis. (ii) Brefeldin A completely inhibited the transport of all [3H]mannose-labeled proteins releasable by phosphatidylinositol-specific phospholipase C, including Thy-1, to the surface of BN-1010-1 cells. Removal of the inhibitor led to rapid reversal of the inhibition. Pulse-chase experiments demonstrated that approximately 50% of Thy-1 was degraded after 4 h in the presence of brefeldin A. (iii) Castanospermine treatment slowed the appearance of Thy-1 on the cell surface. The surface Thy-1 contained mainly normal Man5, Man6, and Man7 oligosaccharides, suggesting that Golgi endo-alpha-D-mannosidase effected the removal of glucose. (iv) Treatment with deoxymannojirimycin resulted in the synthesis of Thy-1 that contained Man8 and Man9 oligosaccharides compared to Man5, Man6, and Man7 in the control. Neither the rate of appearance nor the level of surface expression was affected by the drug. (v) Swainsonine did not affect either the rate of appearance or the level of surface expression of Thy-1. The HPLC elution profile of neutral oligosaccharides resulting from Endo-H digestion of Thy-1 synthesized in the presence of swainsonine was indistinguishable from controls. The lack of an effect of swainsonine is explained by the unexpected absence of a complex type oligosaccharide in Thy-1 of BN-1010-1 cells, as shown in experiments with a variety of lectins as well as digestions with Endo-H or glycopeptidase F, or digestions with both enzymes in sequence. The fact that, after [3H]fucose-labeling, Endo-H digestion produced Thy-1 still labeled with fucose indicates that hybrid oligosaccharide is present in Thy-1.
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PMID:Biosynthetic and structural studies on Thy-1 in a rat neuronal tumor cell line. 809 81

Swainsonine, a known inhibitor of the alpha-mannosidase II involved in processing of asparagine-linked glycoproteins, causes accumulation of hybrid-type oligosaccharide-containing glycoproteins in mammalian cells. Swainsonine augments lymphokine-activated, killer-cell induction at suboptimal doses of interleukin-2; the amount needed to increase LAK activity is 100-1000 fold higher than required to completely inhibit mannosidase II. Human mononuclear lymphocytes, when treated with these relatively high (58 microM) concentrations of swainsonine showed a 3-4 fold increase in D-[3H]mannose incorporation into the glycan as compared to glycans of untreated cells. Analysis indicated accumulation of high-mannose type, free oligosaccharides in the soluble fractions of the cell. Chromatographic analysis of glycan obtained by D-[2-3H]mannose labeling of human mononuclear lymphocytes showed synthesis of a new oligosaccharide, at 58 microM of swainsonine, that contained 36% of the total radioactivity incorporated into the glycan (oligosaccharide pool). This oligosaccharide fraction was resistant to hydrolysis by endoglycosidase H, endoglycosidase F, O and N-glycanase, but was susceptible to cleavage by Jack bean alpha-mannosidase and was bound > 90% to concanavalin A-Sepharose. A similar chromatographic elution profile was obtained from glycans labeled with D-[2-3H]mannose from mouse B16F10 melanoma and baby hamster kidney cells subsequent to swainsonine treatment. Methylation analysis of free oligosaccharides obtained from MNL revealed the presence of a pentamannose. These results indicate the accumulation of a free high-mannose oligosaccharide rather than expected hybrid-type structure on treatment of cells with relatively high concentrations of swainsonine.
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PMID:Accumulation of pentamannose oligosaccharides in human mononuclear leukocytes by action of swainsonine, an inhibitor of glycoprotein processing. 825 42