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)

During meiosis in Saccharomyces cerevisiae, the polysaccharide glycogen is first synthesized and then degraded during the period of spore maturation. We have detected, in sporulating yeast strains, an enzyme activity which is responsible for the glycogen catabolism. The activity was absent in vegetative cells, appeared coincidently with the beginning of glycogenolysis and the appearance of mature ascospores, and increased progressively until spourlation was complete. The specific activity of glycogenolytic enzymes in the intact ascus was about threefold higher than in isolated spores. The glycogenolysis was not due to combinations of phosphorylase plus phosphatase or amylase plus maltase. Nonsporulating cells exhibited litle or no glycogen catabolism and contained only traces of glycogenolytic enzyme, suggesting that the activity is sporulation specific. The partially purified enzyme preparation degraded amylose and glycogen, releasing glucose as the only low-molecular-weight product. Maltotriose was rapidly hydrolyzed; maltose was less susceptible. Alpha-methyl-D-glucoside, isomaltose, and linear alpha-1,6-linked dextran were not attacked. However, the enzyme hydrolyzed alpha-1,6-glucosyl-Schardinger dextrin and increased the beta-amylolysis of beta-amylase-limit dextrin. Thus, the preparation contains alpha-1,4- and alpha-1,6-glucosidase activities. Sephadex G-150 chromatography partially resolved the enzyme into two activities, one of which may be a glucamylase and the other a debranching enzyme.
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PMID:Glycogenolytic enzymes in sporulating yeast. 35 Aug 52

alpha-Glucosidase (EC 3.2.1.20) was purified to homogeneity from logarithmically growing cells of Saccharomyces carlsbergensis. The purification involved the following steps: (a) ammonium sulfate fractionation; (b) Sephadex G-100 chromatography; (c) DEAE-cellulose chromatography; and (d) hydroxylapatite chromatography. This procedure gave a preparation judged to be greater than 98% pure by Na-DodSO4-polyacrylamide gel electrophoresis. The enzyme was shown to be a monomer of 63 000 daltons by gel filtration on Sephacryl S-200 under native conditions and by polyacrylamide gel electrophoresis under denaturing conditions. The Km values of the enzyme for the substrates maltose and p-nitrophenyl alpha-D-glucoside were found to be 1.66 X 10(-2) and 3.1 X 10(-4) M, respectively. The corresponding Vmax value for maltose was 44.8 X 10(-6) mol min(-1) mg(-1) and that for p-nitrophenyl alpha-D-glucoside was 134 X 10(-6) mol min-1 mg-1. The pH optimum for the purified enzyme was found to be between pH 6.7 and 6.8. The enzyme has an absolute anomeric specificity for alpha-glycosidic linkages and appears to recognize a glucosyl residue in alpha linkage on the nonreducing end of its substrate. For the strain used in this study, which carries the MAL 6 locus, only a single form of the enzyme was detected.
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PMID:Purification and characterization of an alpha-glucosidase from Saccharomyces carlsbergensis. 36 20

Brush border membrane vesicles were isolated from rat kidney cortex by differential centrifugation in the presence of 10 mM calcium. Their properties were compared to brush border vesicles isolated by free-flow electrophoresis. By the calcium precipitation method membrane vesicles were obtained in a shorter time with a similar enrichment of brush border marker enzymes (11- to 12-fold for alkaline phosphatase and maltase), with a similarly reduced activity of the marker enzyme for basal-lateral plasma membranes and an almost identical protein composition as revealed by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The transport properties of the two membrane preparations for D-glucose, L-phenylalanine, and phosphate are essentially the same; there is some indication for a lower sodium permeability of the vesicles prepared by the calcium precipitation method. The latter vesicles were also shown to exhibit sodium gradient stimulated uptake of L-glutamate.
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PMID:Properties of brush border vesicles isolated from rat kidney cortex by calcium precipitation. 75 88

Calf pancreas microsomes incorporated radioactively labeled D-glucose from UDP-D-glucose into products extracted with chloroform/methanol (2:1, v/v), chloroform/methanol/water (10:102.5, v/v), and into the residual precipitate, with a pH optimum in Tris/maleate buffer of about 5.3. The chloroform/methanol extract contained a single 14C-labeled acidic product, which was identified as dolichyl beta-D-glucosyl phosphate. It was stable to mild alkali, yielded D-[14C]glucose upon mild acid hydrolysis, and a 14C-labeled compound with the chromatographic mobility of 1,6-anhydro-beta-D-glucopyranosyl upon hot alkali treatment. The [14C]glucolipid had the same chromatographic mobility as dolichyl beta-D-[14C]mannosyl phosphate, and its formation was stimulated by exogenous dolichyl phosphate. The chloroform/methanol/water extract contained radioactive lipid-bound oligosaccharides which were retained on DEAE-cellulose more strongly than dolichyl D-[14C]glucosyl phosphate. They were stable to mild alkali, but labile to acid and hot alkali. Acid treatment yielded a D-glucose-labeled oligosaccharide fraction which was shown by gel filtration to be slightly larger than most of the D-mannose-labeled oligosaccharides. About 80% of the radioactive D-glucose residues could be removed with alpha-glucosidase, but not with beta-glucosidase. Pancreatic dolichyl beta-D-[14C]glucosyl phosphate incubated with calf pancreas microsomes served as direct donor of D-glucosyl residues to lipid-bound oligosaccharides and to the precipitate. These oligosaccharides had the same size as those labeled from UDP-D-[14C]glucose, and the D-[14C]glucose residues could also be removed with alpha-glucosidase.
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PMID:Glucosyltransferase activity in calf pancreas microsomes. Formation of dolichyl D[14C]glucosyl phosphate and 14C-labeled lipid-linked oligosaccharides from UDP-D-[14C]glucose. 84 29

A unique demonstration is presented of the capacity of glycosidases to create anomeric configuration de novo. Purifed Candida tropicalis alpha-glucosidase and sweet almond beta-glucosidase have been found to attack the same substrate, D-glucal, and to convert this unusual glycosyl substrate (which lacks alpha or beta anomeric configuration) to 2-deoxy-alpha-(or beta-) D-glucose, respectively. The stereospecificity of the hydration reaction catalyzed by each enzyme in D2O was revealed by the use of high-resolution (270 MHz) 1H magnetic resonance spectroscopy. The alpha-glucosidase caused a specific axial protonation (deuteration) of D-glucal at C-2, and formation of 2-deoxy-alpha-D-[2(a)-2H]glucose. The beta-glucosidase catalyzed an oppositely directed axial protonation at C-2 and formation of 2-deoxy-beta-D-[2(e)-2H]glucose. These results are not accounted for by the generally accepted mechanisms of carbohydrase action derived from studies with glycosidically linked substrates alone. D-Glucal apparently binds to the enzymes with essentially the same overall orientation as the D-glucosyl moiety of glycosidically linked substrates (with the double bond of D-glucal lying essentially in the plane of the similarly bound D-glucosyl group). Thus, the alpha-glucosidase evidently protonates D-glucal from above the double bond and alpha-D-glucosidic substrates from below the glycosidic oxygen; beta-glucosidase apparently protonates D-glucal from below the double bond and beta-D-glucosides from above the glycosidic oxygen. A detailed mechanism is proposed for the hydration of D-glucal by each enzyme, involving an incipient glycosyl carbonium ion and assuming the presence at the active site of two carboxyl groups arranged to account for catalysis of glycosylations from glycosidically linked substrates. That D-glucal serves as a glycosyl substrate for these enzymes strongly supports the concept that glycosidases and glycosyltransferases are catalysts of glycosylation (i.e., glycosylases), since this concept does not make the usual assumption that carbohydrases are restricted to acting on substrates having a glycosidic bond and either alph- or beta-anomeric configuration.
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PMID:Scope and mechanism of carbohydrase action: stereospecific hydration of D-glucal catalyzed by alpha- and beta-glucosidase. 87 25

At an average of 32 days after a modified Roux-en-y repositioning of rat small intestine, the mucosal mass, mucosal composition, in vivo absorption of galactose and the activity of maltase, sucrase and alkaline phosphatase were measured. In the gut segment with digestive secretions but without food (A) the only change was a decrease of sucrase activity which occurred most probably at the cellular level. In the gut segment with food and gastric juice and a reflux of digestive secretions (B) complex changes took place. An increase in mucosal mass was not accompanied by an increase in galactose absorption. There was a high increase of sucrase activity, a moderate increase of maltase activity and a tendency of the alkaline phosphatase activity to decrease. The changes (increase in mucosal mass and total enzyme activity, but no changes in activity at the cellular level) in the segment exposed to both digestive secretions and food (C) were compatible with a more proximal promotion of a distal gut segment.
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PMID:An experimental model for studies on the effects of food and digestive secretions on the digestive-absorptive capacity of rat small intestine. 89 9

Studies of substrate and cosubstrate specificities of mould alpha-glucosidases suggest that the binding site of the active center of mould alpha-glucosidase consits of two subsites--glucone and aglucone ones. The glucone site is capable to bind glucose and mannose, whereas the aglucone one- some compounds whose affinity for the enzyme may be expressed as follows: glucose greater than galactose greater than paranitrophenol greater than or equal to glycerol greater than ethanol approximately equal to methanol. Upon interaction of enzyme with alpha-D-glucoside the formation of a productive enzyme-substrate complex occurs when the glucosyl residue located at the non-reducible end of the substrate molecule occupies the glucone subsite and aglucone of the substrate occupies the aglucone subsite of the enzyme. After removal of the first product from the aglucone subsite the substrate is bound at this subsite. It is assumed that under cosubstrate excess it is capable to bind at the aglucone subsite prior to the removal of the first product and the formation of the substituted form enzyme--glycosyl. Under these conditions the cosubstrate removes the substrate from the aglucone subsite resulting in a formation of a non-productive tertiary complex enzyme--substrate--cosubstrate. The anomeric configuration of glucose produced under the action of alpha-glucosidase on maltose and starch was determined using a kinetic method.
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PMID:[Specificity of fungal alpha-glucosidases]. 91 42

Endogeneous hyperglucagonemia is observed in experimental diabetes mellitus and semistarvation, conditions associated with an increased intestinal absorptive function. To examine whether glucagon might exert a similar adaptive response on intestinal digestive-absorptive function like experimental diabetes mellitus the effect of chronic glucagon administration on intestinal transport of 3-0-methyl-D-glucose, water, sodium, potassium, and D-glucose induced transmural potential difference (PD) was examined by an in vivo perfusion technique in rat small intestine. Chronic administration of glucagon (100 mug twice daily) for 5 days resulted in increased absorption of 3-0-methyl-D-glucose, water, sodium and potassium as well as in an increase of D-glucose induced PD. A similar, but more pronounced augmentation of D-glucose induced PD was observed in the jejunum of streptozotocin-diabetic rats. Disaccharidase (maltase, sucrase, trehalase, lactase) and alkaline phosphatase activities were not affected in intestinal mucosa of glucagon-treated rats compared to controls. It cannot be decided from these results whether hyperglucagonemia is responsible for the adaptive intestinal changes observed in experimental diabetes mellitus.
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PMID:Effect of chronic glucagon-administration on the digestive and absorptive function of rat small intestine in vivo. 98 1

The latency of the alpha-glucosidase activity of intact rat liver lysosomes was studied by using four substrates (glycogen, maltose, p-nitrophenyl, alpha-glucoside, alpha-fluoroglucoside) at a range of substrate concentrations. The results indicate that the entire lysosome population is impermeable to glycogen and maltose, but a proportion of lysosomes are permeable to alpha-fluoroglucoside and a still higher proportion permeable to p-nitrophenyl alpha-glucoside. Incubation at 37 degrees C in an osmotically protected buffer of of pH 5.0 caused lysosomes to become permeable to previously impermeant substrates and ultimately to release their alpha-glucosidase into the medium. The latencies of lysosomal beta-glucosidase and beta-galactosidase were examined by using p-nitrophenyl beta-glucoside and beta-galactoside as substrates. The results indicate permeability properties to these substrates similar to that to p-nitrophenyl alpha-glucoside. On incubation in an osmotically protected buffer of pH 5, lysosomes progressively released their beta-galactosidase in soluble form, but beta-glucosidase remained attached to sedimentable material. Lysosomal beta-glucosidase was inhibited by 0.1% Triton X-100; alpha-glucosidase and beta-galactosidase were not inhibited.
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PMID:Latency of some glycosidases of rat liver lysosomes. 101 43

The specificity of the hydrolytic reaction has been compared to that of the synthetic reaction for maltase and isomaltase (alpha-methyl-D-glucosidase) from Saccharomyces oviformis. Maltase which hydrolyzes the alpha-1,4-disaccharide, maltose, and the alpha-1,6-disaccharide, isomaltose, catalyzes the formation of both maltose and isomaltose from free glucose. Isomaltase, which hydrolyzes isomaltose but not maltose, catalyzes the formation only of isomaltose from glucose. Both enzymes hydrolyze p-nitrophenyl-alpha-D-glucoside releasing the alpha-anomer of glucose. The enzymes utilize the alpha-anomer but not the beta-anomer for the synthesis of the disaccharides. These results are consistent with the double displacement mechanism for glycosidases and with the proposal that the glucosyl-enzyme complex is an intermediate in the reaction. The competitive inhibition by D-glucose is independent of its anomeric form for both enzymes.
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PMID:The specificity of the synthetic reaction of two yeast alpha-glucosidases. 113 11


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