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)

Rat intestinal surface-membrane glycoproteins were labelled by intraperitoneal injection of [1-(14)C]glucosamine 4h before the animals were killed. At this time, density-gradient centrifugation of disrupted brush borders indicated that glycoprotein radioactivity was distributed identically with sucrase, a plasma-membrane marker. Labelled brush borders were digested by papain for brief time-intervals known to release surface-enzyme particles without disruption of the unit membrane. Digestion for 5min released 90% of the surface sucrase, and almost one-half of the brush-border glycoprotein and label. On Sepharose 4B column chromatography most of the glycoprotein and label emerged as a single peak. This peak contained the most actively labelled glycoprotein in the brush border and was closely associated with maltase, sucrase, beta-naphthylamidase and alkaline phosphatase. The peak was partially resolved on polyacrylamide-gel electrophoresis into three bands. Each band contained a distinctive enzyme or enzyme pair, and was labelled by [1-(14)C]glucosamine. No periodic acid-Schiff-negative protein was observed in the peak material. Glycoproteins susceptible to brief digestion with papain are therefore closely linked to released surface-enzyme particles. Intestinal surface glycoproteins are heterogeneous with respect to molecular weight, electrophoretic mobility and function.
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PMID:Release of intestinal surface-membrane glycoproteins associated with enzyme activity by brief digestion with papain. 511 92

1-Deoxynojirimycin was found to inhibit oligosaccharide processing of rat alpha 1-proteinase inhibitor. In normal hepatocytes alpha 1-proteinase inhibitor was present in the cells as a 49,000 Mr high mannose type glycoprotein with oligosaccharide side chains having the composition Man9GlcNAc and Man8GlcNAc with the former in a higher proportion. Hepatocytes treated with 5 mM 1-deoxynojirimycin accumulated alpha 1-proteinase inhibitor as a 51,000 Mr glycoprotein with carbohydrate side chains of the high mannose type, containing glucose as measured by their sensitivity against alpha-glucosidase, the largest species being Glc3Man9GlcNAc. Conversion to complex oligosaccharides was inhibited by the drug. In addition, increasing concentrations of 1-deoxynojirimycin inhibited glycosylation resulting in the formation of some alpha 1-proteinase inhibitor with two instead of three oligosaccharide side chains. 5 mM 1-deoxynojirimycin inhibited the secretion of alpha 1-proteinase inhibitor by about 50%, whereas secretion of albumin was unaffected. The oligosaccharides of alpha 1-proteinase inhibitor secreted from 1-deoxynojirimycin-treated cells were characterized by their susceptibility to endoglucosaminidase H, incorporation of [3H]galactose, and [3H]fucose and concanavalin A-Sepharose chromatography. It was found that 1-deoxynojirimycin did not completely block oligosaccharide processing, resulting in the formation of alpha 1-proteinase inhibitor molecules carrying one or two complex type oligosaccharides. Only these alpha 1-proteinase inhibitor molecules processed to the complex type in one or two of their oligosaccharide chains were nearly exclusively secreted. This finding demonstrates the importance of oligosaccharide processing for the secretion of alpha 1-proteinase inhibitor.
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PMID:1-deoxynojirimycin impairs oligosaccharide processing of alpha 1-proteinase inhibitor and inhibits its secretion in primary cultures of rat hepatocytes. 622 56

Over 24-h culture with hydrocortisone (400 nM), activity of brush-border alkaline phosphatase, alpha-glucosidase, and leucyl-2-naphthylamidase and cytoplasmic-mitochondrial malate dehydrogenase increased (P less than 0.05) by 80-133% compared with controls. Uptake of 3-O-methyl-D-[14C]glucose after 24-h culture was increased (P less than 0.05) by 30% compared with cultures without hydrocortisone. Labeling of protein with L-[14C]tyrosine and glycoprotein with D-[3H]glucosamine increased (P less than 0.05) by 40 and 88%, respectively, with hydrocortisone. The effects of hydrocortisone were dose dependent at normal serum concentrations (100-600 nM) and not further stimulated by larger concentrations. Cytoplasmic lactate dehydrogenase and lysosomal hexosaminidase activity, specific radioactivity of soluble precursor pools for protein and glycoprotein labeling, incorporation of [3H]thymidine into DNA, and morphology were unaffected by hydrocortisone. Inhibitors of glucocorticoid receptor binding (progesterone), mRNA transcription (alpha-amanitin), and protein synthesis (cycloheximide) prevented the effects of hydrocortisone. We suggest that hydrocortisone maintains the digestive, absorptive, and cellular function of cultured human jejunum. These protective effects were associated with increased protein synthesis and glycosylation and dependent on a classical steroid-hormone mechanism.
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PMID:Protection of epithelial function in human jejunum cultured with hydrocortisone. 634 19

In human kidney cortex neutral alpha-glucosidases 1 and 2 are represented by two forms, soluble (cytosolic) and membrane-bound (brush border) ones. It has been shown that the soluble enzyme preexists in human kidney but does not derive from the membrane-bound form. Similar to the membrane-bound enzyme the soluble form is a glycoprotein. Both enzyme forms possess identical electrophoretic mobility, pH-optimum, heat sensibility and Km values for maltose (0.7 mM) and 4-methylumbelliferyl-alpha-D-glucopyranoside (0.57 mM), but differ by molecular weights as determined by gel filtration chromatography. The molecular weights of the soluble neutral alpha-glucosidases 1 and 2 are lower than those of the comparable brush border enzymes (470 000, 360 000, 520 000 and 440 000, correspondingly). Neutral membrane-bound alpha-glucosidase 1 is a sialylated enzyme with a pI of 4.10 +/- 0.02. The soluble enzyme contains no or only traces of neuraminic acid and has a pI 4.40 +/- 0.03. The soluble and membrane-bound neutral alpha-glucosidases are apparently independent forms of the enzyme, differing by the degree of sialylation and by the presence of an "anchor" in the membrane-bound enzyme. The synthesis of both forms is presumably coded by the same structural gene.
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PMID:[Soluble and membrane-bound neutral alpha-glucosidase from the human kidney]. 636 28

The weanling process is characterized by the transition from a liquid diet poor in iron (rat milk) to a solid diet high in iron (chow pellets). To examine the effects of iron content of the weanling diet on terminal maturation of rat small intestine, suckling pups, nursed by iron-sufficient mothers, were weaned by day 16 onto a solid basal diet that was either deficient [low-iron diet (LID): 0.5 mg iron/100 g solid] or high [high-iron diet (HID) controls: 30 mg iron/100 g solid] in iron. The animals were studied during or at the end of the 4th postnatal wk. By day 17 rats weaned onto the LID exhibited an initial rise in jejunal sucrase activity as did their controls, but the activity plateau of the enzyme was reduced to a level 60% of the controls. On day 28 iron-deprived rats were anemic and showed significant decreases (P less than 0.01 compared with HID rats) in the activity of jejunal sucrase (-57%), neutral lactase (-83%), and maltase (-46%), whereas villus height, crypt depth, mucosal mass parameters, ileal acid beta-galactosidase activity, mucosal protein, and DNA synthesis rates were equivalent in LID and HID groups. The concentration of the secretory component, a glycoprotein synthesized by the intestinal crypt cell, was markedly depressed (P less than 0.01 vs. controls) in the jejunum (-54%) and ileum (-79%) of iron-deprived rats. When D-[1-14C]glucosamine was injected intraperitoneally, incorporation of the label into jejunal and ileal brush-border proteins was two to three times lower for iron-deficient rats than for controls.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Role of dietary iron in maturation of rat small intestine at weaning. 674 22

A horse kidney neutral alpha-D-glucosidase (alpha-D-glucoside glucohydrolase, EC 3.2.1.20) was purified about 580-fold with a yield of 33% by an affinity chromatography technique using the p-aminophenyl-beta-D-maltoside, a substrate derivative, as ligand. The purified enzyme, homogeneous in polyacrylamide gel electrophoresis, was a glycoprotein with a molecular weight of 280 000 as calculated by gel filtration and its isoelectric focusing points was found to be pH 4.1. The purified enzyme was able to hydrolyze various substrates having (alpha-1,2), (alpha-1,3), (alpha-1,4), and (alpha-1,6) glucosidic linkages. The V/Km ratio shows that the (alpha-1,4) linkages are the best substrates. The pKm of the purified enzyme determined at different pH values indicated that two ionizable groups with pK values 5.2 and 6.9 could be essential in the active site. Enzyme modification with cardodiimide abolished the maltase activity. The turanose, a substrate analogue, protected the enzyme against this inactivation.
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PMID:Purification by affinity chromatography and characterization of a neutral alpha-glucosidase from horse kidney. 676

Autolysis of a homogenate from the human gastric mucosa results in the release of the reducing substances into the supernatant. The activities of the six glycosidases from the human gastric mucosa, N-acetyl-beta-glucosaminidase, N-acetyl-Beta-galactosaminidase, alpha-fucosidase, beta-galactosidase, alpha-mannosidase and alpha-glucosidase were determined. Certain properties of the enzymes are described. The significance of these enzymes in glycoprotein catabolism in the human gastric mucosa is discussed.
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PMID:The degradation of glycoconjugates in the human gastric mucous membrane. 679 8

The synthesis of 3-nitro-4-(6-aminohexylamido)phenylboronic acid is described. The properties of two novel forms of immobilized phenylboronate agarose adsorbents [m-aminophenylboronic acid-Matrex Gel and 3-nitro-4-(6-aminohexylamido)phenylboronic acid-Sepharose CL-6B] were investigated. Both gels bind and selectively retard the glycoprotein alpha-glucosidase from yeast. The retardation is affected by following parameters: (i) pH, (ii) presence of sugar, (iii) concentration of sugar and (iv) buffer species (especially triethanolamine). Five sugars were studied, namely sorbitol, fructose, ribose, glucose and maltose. The concentration of sugar required to produce significant retardation increased in the above order, whereas the ability of sugar to form a complex with boron decreases in the same order. These effects were observed with crude as well as pure enzyme. Since alpha-glucosidase is a glycoprotein, it is proposed that this protein is mainly bound to these immobilized phenylboronates via sugar (glyco) residues. Displacement of the enzyme from the column is effected by the sugar in the buffer (or in a preincubation mixture). However, the marked pH-dependence (this retardation effect could only be observed at pH 7.4) suggests that these results are not due solely to hydrophobic or ionic mechanisms and are more complex than simple sugar-phenylboronic acid interactions.
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PMID:Affinity chromatography of yeast alpha-glucosidase using ligand-mediated chromatography on immobilized phenylboronic acids. 703 22

A biochemical study was performed in a Lapland dog suspected of glycogen storage disease type II (acid alpha-glucosidase deficiency, Pompe's disease). Glycogen content was substantially elevated in heart and skeletal muscle but not in the liver. Severely reduced activities of acid alpha-glucosidase (EC 3.2.1.20) were found in heart, skeletal muscle, liver and cultured tongue fibroblasts. The deficiency was located in the glycoprotein fraction, which supported its lysosomal origin. The electrophorogram showed after acid incubation that the affected dog was missing the activity band, while after neutral incubation the pattern was similar to control. The obtained biochemical data are compared with the known data of the human pathology.
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PMID:Canine glycogen storage disease type II. A biochemical study of an acid alpha-glucosidase-deficient Lapland dog. 704 88

Hereditary diabetic mice (NSY) were inbred from original streptozotocin diabetic ICR mice for 8-9 generations using hyperglycemia as an index. The normoglycemic ICR mice were used as controls for the NSY line. The nonfasting blood sugar level of the NSY mice was 305 +/- 14 mg/100ml, while their immunoreactive insulin level was 30 +/- 4 microU/ml (the values of the controls were 165 +/- 12 mg/100 ml and 79 +/- 14 microU/ml, respectively). beta-N-Acetylglucosaminidase [EC 3.2.1.29], beta-galactosidase [EC 3.2.1.23], alpha-glucosidase [EC 3.2.1.21], and alpha-mannosidase [EC 3.2.1.24] activities were determined in the 1,000 X g supernatant of the liver and the kidney of control and streptozotocin diabetic ICR mice and their NSY line. In the kidneys of the insulinopenic NSY mice, the beta-galactosidase and alpha-mannosidase activities were significantly decreased. No significant changes were found in liver enzyme activities. Insulin treatment increased the kidney beta-galactosidase activity signficantly. The insulinopenic state, which caused a decrease in the glycosidase activities in the kidney, could induce retarded breakdown of glycoprotein.
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PMID:Glycosidase activities in the liver and kidney of hereditary diabetic mice. 739 Sep 71


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