Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.20 (alpha-glucosidase)
4,237 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ligand specificity of the human monocyte receptor that mediates phagocytosis of particulate activators of the human alternative complement pathway was defined by inhibiting the phagocytic response with glycans known to be present in zymosan. When monocytes in monolayers were preincubated with 100 micrograms/ml of beta-glucan and then incubated with 1.25 to 2.5 X 10(6) zymosan particles, the percentage of cells that exhibited phagocytosis was inhibited in a time-dependent manner; maximal inhibition occurred within 20 min of preincubation. beta-Glucan inhibited monocyte phagocytosis of zymosan and rabbit erythrocytes (Er) in a similar dose-dependent fashion and at 100 micrograms/ml reduced monocyte ingestion of 5 X 10(6)/ml zymosan and 2 X 10(8)/ml Er by 63 +/- 8% and 68 +/- 16% (mean +/- SD, n = 3), respectively. The other glycan constituent of zymosan, mannan, was less than 1% as active, and 10 mg/ml of mannan reduced the number of monocytes ingesting zymosan and Er by 56 +/- 12% and 26 +/- 11%, respectively. At concentrations as high as 500 micrograms/ml, beta-glucan had no effect on monocyte Fc, C3b, or fibronectin receptor-mediated functions. Enzymatic hydrolysis of beta-glucan and alpha-mannan with beta-glucosidase or beta-glucanase before their incubation with monocytes abrogated their inhibitory capacity, whereas hydrolysis with alpha-mannosidase or alpha-glucosidase did not. Neither of the two alpha-glucans tested (dextran T-70 and nigeran) affected monocyte ingestion of zymosan particles or sheep erythrocytes (Es) sensitized with rabbit 7S anti-Es (EsIgG) at concentrations as high as 2 mg/ml. In contrast, a number of beta-glucans were active against zymosan but not EsIgG ingestion with a 75% reduction in the number of monocytes ingesting zymosan occurring with 100 micrograms/ml laminarin, 500 micrograms/ml soluble pachyman, and 900 micrograms/ml of soluble pustulan. The galactan, agarose, either in suspensions at 2 mg/ml or in a soluble portion at 600 micrograms/ml failed to affect monocyte ingestion of zymosan particles or Er. Thus, the monocyte receptor for particulate activators that is specifically inhibited by beta-glucan at a rate compatible with a phagocytic process and that recognizes beta-glucans but not alpha-glucans, mannan, or galactan is a beta-glucan receptor.
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PMID:A beta-glucan inhibitable receptor on human monocytes: its identity with the phagocytic receptor for particulate activators of the alternative complement pathway. 257 46

Adler and Martin (1983, Curr. Eye Res. 2, 359-66) found cathepsin D to be present in crude preparations of bovine interphotoreceptor matrix (IPM). The purpose of the present study was to determine, by investigating several acid hydrolases in purer IPM samples, whether hydrolytic enzymes abundant in RPE lysosomes were present also as normal components of the IPM. IPM was prepared from bovine eyes by the introduction of a small bleb of buffer between the neural retina and the RPE. These IPM samples were free from significant contamination by surrounding tissues; they contained IRBP as their only major protein, and had negligible amounts of lactate dehydrogenase and ROS-specific proteins. Most acid hydrolases were assayed fluorometrically by measuring the 4-methylumbelliferone released upon hydrolysis of appropriate derivatives; the substrate for cathepsin was hemoglobin. The amounts of the enzymes found in the IPM were far from uniform and could not be correlated with enzyme activities in either RPE or retina homogenates. The hydrolases in the IPM varied in amount from beta-galactosidase (28% of the RPE level), through N-acetyl-beta-glucosaminidase (20%), alpha-fucosidase (15%), beta-glucuronidase (12%), alpha-glucosidase (8%), cathepsin D (7%), alpha-mannosidase (7%), down to beta-glucosidase, acid phosphatase, and acid lipase (trace amounts, less than 1%). These results agree with the relative amounts of enzymes found by Wilcox (1987) to be secreted into the medium by cultured human RPE cells. Furthermore, the rank order of hydrolases in the IPM is the same as that for hydrolases secreted (but not recaptured) by human fibroblasts in I-cell disease. The conclusion from these correlations is that lysosomal enzymes are probably secreted, as a normal process, by the RPE into the IPM, where they may have a role in digesting shed outer segments and in catabolizing IPM components.
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PMID:Selective presence of acid hydrolases in the interphotoreceptor matrix. 261 85

The first steps of the biosynthetic pathway of high molecular weight polylactosamine-type glycopeptides from rat Zajdela hepatoma cells were studied by pulse-chase experiments, biochemical analysis and by inhibition of N-glycosylation. It is clear that this process involves firstly the transfer of a lipid-linked high-mannose oligosaccharide precursor to a protein moiety in a similar way to that of N-linked glycopeptides of a more common size range according to the classical 'cycle of dolichol'. In the presence of enzymes which are inhibitors of the processing of high-mannose oligosaccharide chains, this class of oligosaccharides was considerably increased, whereas polylactosamine chains and lower complex N-linked glycopeptides were concomitantly decreased in the same kinetics and the same ratio. As expected in the presence of N-methyldeoxynojirimycin, which is an alpha-glucosidase inhibitor, high-mannose oligosaccharides remained glycosylated and are mostly of the Glc1-3Man9GlcNAc type. In the presence of swainsonine, which is an alpha-mannosidase (EC 3.2.1.24) inhibitor, these chains were devoid of glucose residues. In addition, some chains displayed hybrid structures. It appears, therefore, that the first steps of the biosynthesis of polylactosamine-type and N-linked oligosaccharides of a more common size range proceed similarly and that differences between their biosynthetic pathways occur during the elongation phase, which leads to their final respective structures. Glycopeptides prepared from the cell surface by mild trypsin treatment as well as from entire cells, previously treated or not by processing inhibitors, display the same gel filtration patterns indicating that modifications in protein glycosylation do not prevent glycoprotein insertion into the cell membrane.
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PMID:Biosynthesis of high molecular weight polylactosamine-type glycopeptides in rat Zajdela hepatoma ascites cells. 271 99

Normal arterial foci which take up Evans blue dye (EBD) in vivo are believed to represent atherosclerosis-prone, hemodynamically stressed foci compared to areas which exclude dye. We have used the rabbit EBD model to examine focal aortic hydrolases of blue areas versus white areas, and we report herein significant focal variations of hydrolase activities. Enzymes measured included neutral alpha-glucosidase, N-acetyl-beta-glucosaminidase, alpha-mannosidase, acid alpha-glucosidase, beta-galactosidase, beta-glucuronidase, cathepsin C, and acid cholesteryl esterase (ACE); specific activities were expressed on the basis of tissue DNA. In correlative areas of EBD uptake in normal rabbit aortic arch, ACE activity averaged 17% higher and cathepsin C activity averaged 37% lower than activities of areas free of EBD in the descending thoracic aorta (P less than 0.02). None of the glycosidases studied differed significantly between blue and white aortic areas. These findings indicate that discrete, intrinsic differences of hydrolytic enzyme activities exist in the normal rabbit aorta in areas delineated by in vivo EBD uptake, areas recognized as lesion-prone vs lesion-resistant.
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PMID:Intrinsic focal variations of rabbit aortic hydrolase activities. 276 19

Flavonoids (103 species) were tested for inhibitory activity against mouse liver sialidase using sodium p-nitrophenyl-N-acetyl-alpha-D-neuraminate (PNP-NeuAc) as substrate. Isoscutellarein-8-O-glucuronide from the leaf of Scutellaria baicalensis showed most potent activity (IC50, 40 microM), and this flavone appeared to be a non-competitive inhibitor of the enzyme. This flavone inhibited the lysosomal solubilized sialidase against PNP-NeuAc and sialyllactose effectively, but not microsomal enzyme against gangliosides and colominic acid, whereas, negligible or weak inhibitory activities were observed for influenza virus sialidase, beta-galactosidase, alpha-mannosidase, and alpha-glucosidase tested. These results indicate that this flavone may be useful to elucidate the function of the lysosomal solubilized sialidase.
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PMID:Inhibition of mouse liver sialidase by plant flavonoids. 277 64

Post-mortem brain samples from patients with either Huntington's disease, Alzheimer-type dementia or appropriate controls were assayed for endoplasmic reticulum enzymes, NADPH-cytochrome c reductase, neutral alpha-glucosidase, inosine diphosphatase, alpha-mannosidase and glucose-6-phosphatase and for Golgi enzymes, fucosyl- and galactosyl-transferases. In Alzheimer-type dementia there was a selective decrease in alpha-glucosidase activity in the temporal cortex. In Huntington's disease there was a selective decrease of putamen alpha-glucosidase and fucosyl-transferase activities. It is suggested that these changes reflect highly specific alterations in glycoprotein synthesis and processing and may contribute to the underlying pathology of these disorders.
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PMID:Loss of endoplasmic reticulum-associated enzymes in affected brain regions in Huntington's disease and Alzheimer-type dementia. 293 94

A number of lysosomal enzymes are secreted from Tetrahymena pyriformis during growth and during starvation. The secretion is energy-dependent and kinetically different among hydrolases. On the basis of the secretion kinetics under starvation conditions, Tetrahymena hydrolases can be separated into three classes. The first group containing acid phosphatase, beta-glucosidase and alpha-galactosidase, are secreted slowly. Within this group about 4% of the initial cellular activity is released per hour. The second group of enzymes, including alpha-glucosidase, alpha-mannosidase and beta-galactosidase, exhibit moderate secretion (11-15% of the initial cellular activity per hour). The third group, N-acetyl-beta-hexosaminidase, has the highest rate of secretion (22% of the initial cellular activity per hour). N-Acetyl-beta-hexosaminidase shows a continuous increase in overall activity during starvation, which is completely blocked by adding cycloheximide; its secretion is also suppressed. Such involvement of enzyme biosynthesis was not seen in the first and second groups. Furthermore, treatment with weak bases caused inhibited secretion of differing degree among acid phosphatase (group I), alpha-glucosidase (group II) and N-acetyl-beta-hexosaminidase (group III).
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PMID:Secretion heterogeneity of lysosomal enzymes in Tetrahymena pyriformis. 295 37

The epidermal growth factor receptor in cells of the UMR 106-06 clonal osteoblast line has been shown to be structurally similar to that previously characterized in other cell lines. A specific receptor component of approximately 165,000-185,000 Mr has been identified by polyacrylamide gel electrophoresis using the chemical crosslinker disuccinimidyl suberate to crosslink 125I-EGF to its receptor. Tunicamycin treatment of cells resulted in a dose-dependent loss of binding suggesting involvement of glycosyl moieties in EGF binding to its receptor. Competitive binding studies carried out using wheat germ lectin (WGL), concanavalin A (CON.A.), soybean lectin (SBL), and lentil lectin (ILL) to compete for binding of 125I-EGF revealed that CON A, WGL, and to a lesser extent LL could inhibit EGF binding; SBL was without effect. Treatment of the cells with neuraminidase which cleaves terminal sialic acid residues resulted in total loss of binding while alpha-glucosidase, beta-N-acetylglucosaminidase and alpha-mannosidase were without effect. These data indicate a specific interaction of EGF with terminal sialic acid residues of the EGF receptor. However, it would seem that the mannose residues which appeared to modify EGF binding were not available for the action of the above enzymes due to the presence of sialic acid.
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PMID:Molecular characterization of the EGF receptor and involvement of glycosyl moieties in the binding of EGF to its receptor on a clonal osteosarcoma cell line, UMR 106-06. 300 87

Activities of 10 lysosomal hydrolase enzymes (beta-hexosaminidase, beta-galactosidase, alpha-galactosidase, alpha-mannosidase, beta-mannosidase, alpha-L-fucosidase, beta-glucuronidase, alpha-glucosidase, alpha-N-acetylgalactosaminidase, and acid phosphatase) were determined in eight organs (brain, liver, kidney, spleen, heart, skeletal muscle, lung, and testis) in males and females of six inbred mouse strains (C57BL/6J, C3H/HeJ, DBA/2J, BALB/cJ, P/J, and 129/J). Examples of enzyme-specific variation, organ-specific variation, and enzyme- and organ-specific variation were found. New enzyme-specific variants with the features of systemic regulators for alpha-L-fucosidase and beta-mannosidase were found. Known variants were detected. Organ-specific variants had some of the properties expected for a new class of genes affecting multiple enzymes: organ-specific regulators.
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PMID:Variation in ten lysosomal hydrolase enzyme activities in inbred mouse strains. 302 5

We examined specific activities (based on DNA) of six glycosidases and cathepsin C in aorta, kidney, and liver from male rats of 2, 6, 10, and 14 months of age. The premise was that assessing cellular catabolism of arterial and nonvascular tissues over age might more fully clarify the impact of age (and growth) alone upon vascular wall metabolism. All aortic glycosidases increased significantly (P less than 0.05) over the holding period as follows: neutral alpha-glucosidase, up 93%; beta-galactosidase, up 102%; N-acetyl-beta-glucosaminidase, up 119%; alpha-mannosidase, up 77%; beta-glucuronidase, up 65%; acid alpha-glucosidase, up 95%. Cathepsin C specific activity was unchanged as was aortic DNA content; total protein content increased 136%. In the kidney, all glycosidase specific activities declined over age with decreases ranging 39-55%; cathepsin C was unchanged. In the liver, neutral alpha-glucosidase increased 12%, acid alpha-glucosidase was unchanged, and the four remaining glycosidases decreased an average of 5-35% by 14 months of age. Liver cathepsin C decreased 44% over this period. Thus, enhancement of hydrolase baseline activities prevails during growth and aging in rat aortic tissue whereas hydrolases of kidney and liver tissues generally decline.
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PMID:Hydrolase activities increase in the rat aorta with growth and aging but not in liver and kidney. 309 18


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