Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.4.99.6 (sialyltransferase)
 1,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

alpha 1-Antitrypsin phenotypes Pi M and Z, purified by the thiol-disulfide exchange procedure, were desialylated by treatment with neuraminidase covalently coupled to Sepharose and used as acceptors of sialic acid in an assay system for serum sialic acid transferase (CMP-N-acetylneuraminate:D-galactosyl-glycoprotein N-acetylneuraminyltransferase, EC 2.4.99.1) activity. Both asialoantitrypsins were equally effective as acceptors in contrast to native Pi Z antitrypsin which did not accept any sialic acid. Serum sialyltransferase activity was determined in 38 adult alpha 1-antitrypsin deficient individuals (Pi Z, MZ, FZ, SZ) with normal liver function and was found to be of the same magnitude as the activity in normal individuals (Pi M). Equal activities were also found in 5 Pi Z patients with cirrhosis of the liver. The results strongly argue against the concept that sialyltransferase deficiency provides the molecular basis for alpha 1-antitrypsin deficiency.
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PMID:The serum sialyltransferase activity in alpha 1-antitrypsin deficiency. 108 69

We are interested in determining whether carbohydrates are important regulatory determinants in the intracellular transport and secretion of glycoproteins. In the present study, we have used swainsonine, an indolizidine alkaloid, to modify the structure of N-glycosidically linked complex oligosaccharides. By inhibiting Golgi mannosidase II, swainsonine prevents the trimming of GlcNAc(Man)5(GlcNAc)2 to GlcNAc-(Man)3(GlcNAc)2, resulting in the formation of hybrid-type oligosaccharides. We find, from pulse-chase experiments using [35S]methionine and immunoprecipitation of individual proteins from culture media, that swainsonine treatment (1 microgram/ml) accelerated the secretion of glycoproteins (transferrin, ceruloplasmin, alpha 2-macroglobulin, and alpha 1-antitrypsin) by decreasing the lag period by 10-15 min relative to untreated cultures. The enhanced secretion was specific for glycoproteins since the secretion of albumin, a nonglycoprotein, was unaffected. When alpha 1-antitrypsin was immunoprecipitated from the cell lysates, sodium dodecyl sulfate-polyacrylamide gel electrophoresis fluorographic analysis demonstrated that the conversion of the high-mannose precursor to the hybrid form in swainsonine-treated cells occurred more rapidly (by about 10 min) than the conversion to the complex form in control cells. Since both the hybrid and complex forms of alpha 1-antitrypsin are terminally sialylated by sialyltransferase in the trans-Golgi, these results suggest that swainsonine-modified glycoproteins traverse the Golgi more rapidly than their normal counterparts. Therefore, accelerated transport within this organelle may account for the decreased lag period of glycoprotein secretion in the swainsonine-treated cultures.
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PMID:Swainsonine treatment accelerates intracellular transport and secretion of glycoproteins in human hepatoma cells. 257 69