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)

Using accumulating preparations of the mucose, studies have been made on the rate of accumulation of the glucose from 11 mM solutions of glucose, maltose and starch in proximal, intermediate and distal parts of the small intestine of 2--13-week rats. It was demonstrated that in 2-week animals, rather intensive transmembrane transport of "free" glucose takes place in the proximal and medial parts of the small intestine, the transport of glucose in the form of maltose or starch being absent. At later stages of postnatal life, especially to the onset of definitive nutrition, together with the induction of alpha-glucosidase systems, gamma-amylase and maltase transporting mechanisms are formed which provide for the adaptation of the organism to qualitatively new feeding conditions.
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PMID:[Postnatal formation of the mechanisms of carbohydrate hydrolysis and transport in the rat small intestine]. 51 43

Camels with cannulas in the small intestine were used to study the "digestive-absorptive" capacities of the small intestine. Solutions of different carbohydrates were infused through the cannulas and the responses in blood glucose levels were measured. Monosaccharides were readily absorbed from the camel small intestine. The pattern of disaccharide absorption indicated that there was high lactase activity and low maltase and sucrase activity, in the camel small intestinal mucosa.
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PMID:Studies on the digestion of carbohydrates in the camel (Camelus dromedarius). 59 40

Disaccharidases activities in 20-day-old chick embryonic intestine were induced by the addition of sucrose, maltose, fructose and glucose to the culture medium. However, maltitol, which cannot be digested by intestinal enzymes, showed no effect on the induction of disaccharidase activity. Kinetic study of the enzymes demonstrated that the maximum velocity (Vmax) and the Michaelis constant (Km) of sucrose induced disaccharidases activities of the explants showed changes similar to those observed in the chick of same developmental stage in vivo. Namely, Vmax values of sucrase and maltase were increased. Km values of sucrase did not change, but that of maltase showed a significant decrease during development.
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PMID:Effect of various sugars on the induction of chick embryonic intestinal disaccharidases in the organ culture system. 69 Jul 28

The role of mitochondria in carbon catabolite repression in Saccharomyces cerevisiae was investigated by comparing normal, respiratory competent (RHO) strains with their mitochondrially inherited, respiratory deficient mutant derivatives (rho). Formation of maltase and invertase was used as an indicator system for the effect of carbon catabolite repression on carbon catabolic reactions. Fermentation rates for glucose, maltose and sucrose were the same in RHO and rho strains. Specific activities of maltase and invertase were usually higher in the rho-mutants. A very pronounced difference in invertase levels was observed when cells were grown on maltose; rho-mutants had around 30 times more invertase than their RHO parent strains. The fact that rho-mutants were much less sensitive to carbon catabolite repression of invertase synthesis than their RHO parents was used to search for the mitochondrial factor(s) or function(s) involved in carbon catabolite repression. A possible metabolic influence of mitochondria on this system of regulation was tested after growth of RHO strains under anaerobic conditions (no respiration nor oxidative phosphorylation), in the presence of KCN (respiration inhibited), dinitrophenol (uncoupling of oxidative phosphorylation) and of both inhibitors anaerobic conditions and dinitrophenol had no effect on the extent of invertase repression. KCN reduced the degree of repression but not to the level found in rho-mutants. A combination of both inhibitors gave the same results as with KCN alone. Erythromycin and chloramphenicol were used as specific inhibitors of mitochondrial protein synthesis. Erythromycin prevented the formation of mitochondrial respiratory systems but did not induce rho-mutants under the conditions used. However, repression of invertase was as strong as in the absence of the inhibitor. Chloramphenicol led only to a slight reduction of the respiratory systems and did not affect invertase levels. A combination of both antibiotics had about the same effect as growth in the presence of KCN. The results showed that mitochondria are involved in carbon catabolite repression and they cause an increase in the degree of repression. These effects cannot be due to mere metabolic activities nor to factors made on the mitochondrial protein synthesizing machinery. This regulatory role of mitochondria is observed as long as an intact mitochondrial genome is maintained.
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PMID:The role of mitochondria in carbon catabolite repression in yeast. 79 Jan 58

The alpha-glucosidase (alpha-D-glucoside glucohydrolase, EC 3.2.1.20) of Pseudomonas fluorescens W was partially purified by (NH4)2SO4 fractionation, Sephadex G-200 and DEAE-cellulose column chromatography. The enzyme showed great specificity for maltose hydrolysis, with very little action against polymeric forms. Sucrose, isomaltose, alpha-methylglucoside, and maltobionic acid were not hydrolyzed. Turanose was a strong competitive inhibitor, and glucose a weaker one. Tris (2-amino-2-hydroxymethylpropan-1:3-diol) inhibited enzyme activity significantly only at alkaline pH. Mercuric, cupric, and silver cations strongly inhibited, and EDTA (ethylenediaminetetraacetate) weakly inhibited the enzyme. The isolated enzyme was rather unstable even at 4 degrees C, and was destroyed by freezing and lyophilization. Inositol and albumin had a slightly protective effect. Sulfhydryl-binding reagents strongly inhibited the enzyme.
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PMID:Partial purification and characterization of alpha-glucosidase from Pseudomonas fluorescens W. 81 70

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

The effects of carbohydrate intake on jejunal disaccharidases in rats with chronic mannitol-induced, osmotic diarrhea were studied. Weanling rats were force-fed 5 ml/100 g of body weight of water of 20% mannitol (w/v 1300 mOsm) daily for up to 14 days. Diets containing 70% of either starch, sucrose, glucose, or 20% lactose with 50% starch were fed ad libitum. Mannitol-fed rats had increased water intake and diarrhea. They gained weight, but less than controls. The levels of intestinal disaccharidases in mannitol-fed rats were related to dietary carbohydrate intake. Seven days of mannitol treatment led to lactase and sucrase deficiencies in rats fed starch whereas jejunal maltase and alkaline phosphatase were unchanged. Deficiencies in lactase and maltase but not in sucrase were induced when rats were fed a sucrose diet, while a decrease only in sucrase occurred in rats fed a lactose-starch diet. Rats with mannitol-induced diarrhea fed a glucose diet had reduced levels of all disaccharidases. The changes in intestinal disaccharidases were not associated with alterations in the number of epithelial cells or ultrastructural abnormalities. 3H-thymidine incorporation into DNA following 7 days of mannitol treatment was similar to water-fed controls. Absorptive epithelial cells were not damaged and the microvilli were normal in height and appearance. These data suggest that the levels of specific disaccharidases show and enhanced dependence upon the corresponding dietary substrates during diarrhea induced by an osmotic load.
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PMID:Interaction between dietary carbohydrates and intestinal disaccharidases in experimental diarrhea. 85 Oct 74

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

Enzymes capable of hydrolyzing cell walls of Blastomyces dermatitidis and chemotypes I and II of Histoplasma capsulatum were prepared in the laboratory or obtained from commercial sources. They included chitinases, beta-1,3-glucanases, beta-1,6-glucanase, and Pronase. Monosaccharides and disaccharides of glucose released from the cell walls by the enzymes were determined qualitatively by paper and gas-liquid chromatography, and monosaccharides were quantitated by the latter technique as well. An enzyme system isolated from Streptomyces sp. containing both chitinase and glucanase released maximum amounts of glucose and N-acetylglucosamine from the cell walls of H. capsulatum chemotype I. A chitinase preparation, free of glucanase, from Serratia marcescens released only chitobiose and N-acetylglucosamine from chemotype I cell walls, but the total quantity of N-acetylglucosamine released was about 60% less than that released by the Streptomyces system. A beta-1,3-glucanase from Bacillus circulans hydrolyzed the cell walls of H. capsulatum chemotype I, but a beta-1,6-glucanase failed to release glucose from the same walls. Autolytic enzymes, viz., beta-1,3-glucanases and several glycosidases were detected as constitutive enzymes in both yeast and mycelial phases of B. dermatitidis and H. capsulatum chemotypes I and II. No difference in the amount of activity was found between cell sap and culture filtrate preparations. The beta-glucanases prepared from the Histoplasma and Blastomyces strains were active on the cell walls of the yeast phases of H. capsulatum chemotypes I and II, releasing laminaribiose and glucose, but were essentially inactive on the cell walls of B. dermatitidis. Chitinase, beta-1,6-glucanase, alpha-glucanase, and alpha-glucosidase activities were absent from these fungal enzyme preparations.
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PMID:Cell wall studies of Histoplasma capsulatum and Blastomyces dermatitidis using autologous and heterologous enzymes. 87 Apr 37

Chronic application (20 days) of glucagon in pharmacological doses induces mucosal transformation of the hyperregenerative type in the small intestine of the rat. This transformation is characterized by decreased villi, and increased crypt length. The morphological changes are accompanied by a reduction in glucose absorption in vivo as well as by decreased activities of lactase, sucrase and maltase. The findings demonstrate that hyperglucagonemia is not the cause for hyperplastic mucosal transformation, which is found in the experimental diabetes in the rat.
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PMID:[Functional and morphological studies on intestinal mucosa of the rat under chronic glucagon application (author's transl)]. 88 15


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