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)

Acid maltase deficiency in adults is associated with progressive muscle weakness and may effect respiratory muscles resulting in respiratory failure. The biochemical and clinical manifestations of acid maltase deficiency arise from a marked deficiency of the lysosomal enzyme alpha-glucosidase (acid maltase), which normally degrades glycogen to free glucose. In the past few years, high-protein diets have provided an alternative energy source for these patients and resulted in improved muscle strength. Recently, we treated a ventilator-dependent acid maltase-deficient patient with a general diet supplemented with branched-chain amino acids. Branched-chain amino acids are the principal amino acids involved in muscle protein synthesis and utilization. While on this diet, the patient had improvement of respiratory function and muscle strength and was able to be weaned from the ventilator during the day. In addition to his nutritional status, levels of serum branched-chain amino acids, showed improvement within 2 months after the diet started. This diet shows potential advantages over a high-protein diet without supplemented branched-chain amino acids for the treatment of acid maltase deficiency. These include theoretical sparing of amino acids required for muscle protein synthesis by providing higher concentrations of postprandial branched-chain amino acids in the circulation. Also, the liquid formula would be better tolerated by a ventilator-dependent or debilitated patient rather than a high-protein general diet. Further experience with branched-chain amino acid formulas will be needed to substantiate their efficacy in the treatment of acid maltase deficiency.
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PMID:Treatment of acid maltase deficiency with a diet high in branched-chain amino acids. 211 30

Aspergillus niger alpha-D-glucosidase, crystallized and free of detectable activity for beta-D-glucosides, catalyzes the slow hydrolysis of beta-D-glucopyranosyl fluoride to form alpha-D-glucose. Maximal initial rates, V, for the hydrolysis of beta-D-glucosyl fluoride, p-nitrophenyl alpha-D-glucopyranoside, and alpha-D-glucopyranosyl fluoride are 0.27, 0.75, and 78.5 mumol.min-1.mg-1, respectively, with corresponding V/K constants of 0.0068, 1.44, and 41.3. Independent lines of evidence make clear that the reaction stems from beta-D-glucosyl fluoride and not from a contaminating trace of alpha-D-glucosyl fluoride, and is catalyzed by the alpha-D-glucosidase and not by an accompanying trace of beta-D-glucosidase or glucoamylase. Maltotriose competitively inhibits the hydrolysis, and beta-D-glucosyl fluoride in turn competitively inhibits the hydrolysis of p-nitrophenyl alpha-D-glucopyranoside, indicating that beta-D-glucosyl fluoride is bound at the same site as known substrates for the alpha-glucosidase. Present findings provide new evidence that alpha-glucosidases are not restricted to alpha-D-glucosylic substrates or to reactions providing retention of configuration. They strongly support the concept that product configuration in glycosylase-catalyzed reactions is primarily determined by enzyme structures controlling the direction of approach of acceptor molecules to the reaction center rather than by the anomeric configuration of the substrate.
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PMID:Hydrolysis of beta-D-glucopyranosyl fluoride to alpha-D-glucose catalyzed by Aspergillus niger alpha-D-glucosidase. 219 75

A new indolizidine alkaloid has been isolated from the seeds of Castanospermum [1] australe and identified as 7-deoxy-6-epi-castanospermine by ms and 1H- and 13C-nmr spectroscopy. The alkaloid is the first trihydroxylated indolizidine to be isolated from this plant and may represent an intermediate in the biosynthetic pathway to the tetrahydroxy-indolizidines and -pyrrolizidines. It inhibits amyloglucosidase and yeast alpha-glucosidase but is significantly less active as a glycosidase inhibitor than its isomer swainsonine [2] and the tetrahydroxylated alkaloids castanospermine [3], 6-epi-castanospermine [4], and australine [5].
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PMID:7-deoxy-6-epi-castanospermine, a trihydroxyindolizidine alkaloid glycosidase inhibitor from Castanospermum australe. 221 32

Three pseudo-aminosugars, validamine, valienamine and valiolamine, produced by Streptomyces hygroscopicus subsp. limoneus showed potent inhibitory action on rat small intestinal carbohydrase activities such as sucrase, maltase, glucoamylase, isomaltase and trehalase activities, but negligible action on lactase activity and pancreatic alpha-amylase activity. Where inhibition was seen, kinetic analysis showed fully competitive inhibition of the carbohydrase activities by all three inhibitors. Valiolamine has more potent carbohydrase inhibitory activity than validamine or valienamine, and the apparent Ki values of valiolamine for sucrase, maltase, glucoamylase, isomaltase and trehalase activities were 3.2 x 10(-7), 2.9 x 10(-6), 1.2 x 10(-6), 9.1 x 10(-7) and 4.9 x 10(-5) M, respectively, which are 10(-5) to 10(-3) times smaller than the apparent Km values.
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PMID:Inhibitory effect of validamine, valienamine and valiolamine on activities of carbohydrases in rat small intestinal brush border membranes. 226 98

Lentiginosine, a dihydroxyindolizidine alkaloid, was extracted from the leaves of Astragalus lentiginosus with hot methanol and was purified to homogeneity by ion-exchange, thin-layer, and radial chromatography. A second dihydroxyindolizidine, the 2-epimer of lentiginosine, was also purified to apparent homogeneity from these extracts. Gas chromatography of the two isomers (as the TMS derivatives) showed that they were better than 95% pure; lentiginosine eluted at 8.65 min and the 2-epimer at 9.00 min. Both compounds had a molecular ion in their mass spectra of 157, and the NMR spectra demonstrated that both were dihydroxyindolizidines differing in the configuration of the hydroxyl group at carbon 2. Lentiginosine was found to be a reasonably good inhibitor of the fungal alpha-glucosidase, amyloglucosidase (Ki = 1 x 10(-5) M), but it did not inhibit other alpha-glucosidases (i.e., sucrase, maltase, yeast alpha-glucosidase, glucosidase I) nor any other glycosidases. The 2-epimer had no activity against any of the glycosidases tested.
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PMID:Lentiginosine, a dihydroxyindolizidine alkaloid that inhibits amyloglucosidase. 233 69

The influences of glucose, the benzothiadiazide derivative diazoxide (an inhibitor of insulin release), and the potent non-glucose insulin secretagogue 3-isobutyl-1-methylxanthine (IBMX) on insulin secretion and the activities of 3 different lysosomal enzymes were studied in isolated mouse islets. We found that the increase in insulin secretion during a 4 hr incubation period in the presence of 16.7 mM glucose was accompanied by an increase in islet activities of the lysosomal enzymes acid amyloglucosidase and acid alpha-glucosidase. These alpha-1,4-glucoside splitting enzyme activities were increased by 45-55% (p less than 0.01). No influence by glucose was encountered for the activities of N-acetyl-beta-D-glucosaminidase or the non-lysosomal neutral alpha-glucosidase. Upon incubation with 0.2 mM diazoxide and glucose (16.7 mM) the glucose-induced insulin secretion was markedly suppressed and no significant increase in islet lysosomal enzyme activities was observed. On the other hand, insulin secretion induced by IBMX to the same magnitude as with 16.7 mM glucose, was accompanied by an increase in islet activity of N-acetyl-beta-D-glucosaminidase (p less than 0.05), whereas no apparent changes in acid amyloglucosidase and acid alpha-glucosidase activities could be detected. In conclusion, the determination of lysosomal enzyme activities in isolated mouse islets revealed that glucose was able to induce an increased activity of glucose producing glycogenolytic acid hydrolases under conditions when a concomitant insulin secretion occurred.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Insulin secretion and lysosomal enzyme activities in isolated mouse islets. Effects of glucose, diazoxide and isobutylmethylxanthine. 243 78

Amylases possess short, conserved regions near functional side chains. Sequence comparison extends this relationship to comprise a maltase and a cyclodextrin glucanotransferase. Similarity also exists with intestinal sucrase-isomaltase and fungal glucoamylase near identified essential carboxyl groups. Homology between COOH-terminal regions of glucoamylase and cyclodextrin glucanotranserase may indicate raw-starch binding areas. It is suggested that amylases, alpha-glucosidases, and transglucanosylases acting on 1,4- and 1,6-alpha-glucosidic linkages share key structural features in the active centres.
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PMID:Regional distant sequence homology between amylases, alpha-glucosidases and transglucanosylases. 245 Jul 87

The effect of chronic intragastric infusion of hypertonic mannitol on small intestinal mucosal structure and function was studied in adult rats. Animals were gavage-fed 20% mannitol (1300 mosm) at a dose of 5 ml/100 g body weight daily for seven days. Control animals were gavage-fed tap water on the same schedule. On day 8, the animals were anesthetized, the duodenum cannulated, and a test sugar (glucose, glucose polymer, lactose, sucrose, or maltose) was infused at a dose of 0.5 g/kg body weight in 2.5 ml distilled water over less than 1 min. Portal vein glucose was measured at 30-min intervals from 0 to 120 min. Mannitol treatment resulted in histologic and biochemical alterations (reduced lactase, sucrase, maltase) limited to the proximal small intestine compared to the control group. The absorption of glucose and glucose polymers was similar in mannitol-treated and control animals. In contrast, digestion and absorption of lactose, sucrose, and maltose was significantly diminished in mannitol-treated animals when compared to controls. No changes in permeability to polyethylene glycol 4000 or Na+-coupled glucose transport were observed in mannitol-treated animals compared to controls. These data suggest that when the intestinal mucosa is exposed to hyperosmolar loads that the digestive capacity for disaccharides is suppressed more than its glucose absorptive capacities. Furthermore, glucose oligomers may be more readily digested and absorbed than disaccharides, in this setting, due, in part, to the proximal injury and less pronounced proximal-distal gradient for glucoamylase than other brush-border carbohydrases.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Proximal small intestinal mucosal injury. Maintenance of glucose and glucose polymer absorption, attenuation of disaccharide absorption. 249 65

Australine [(1R,2R,3R,7S,7aR)-3-(hydroxymethyl)-1,2,7-trihydroxypyrrolizid ine] is a polyhydroxylated pyrrolizidine alkaloid that was isolated from the seeds of the Australian tree Castanospermum australe and characterized by NMR and X-ray diffraction analysis [Molyneux et al. (1988) J. Nat. Prod. (in press)]. Since swainsonine and catanospermine are polyhydroxylated indolizidine alkaloids that inhibit specific glycosidases, we tested australine against a variety of exoglycosidases to determine whether it would inhibit any of these enzymes. This alkaloid proved to be a good inhibitor of the alpha-glucosidase amyloglucosidase (50% inhibition at 5.8 microM), but it did not inhibit beta-glucosidase, alpha- or beta-mannosidase, or alpha- or beta-galactosidase. The inhibition of amyloglucosidase was of a competitive nature. Australine also inhibited the glycoprotein processing enzyme glucosidase I, but had only slight activity toward glucosidase II. When incubated with cultured cells, this alkaloid inhibited glycoprotein processing at the glucosidase I step and caused the accumulation of glycoproteins with Glc3Man7-9(GlcNAc)2-oligosaccharides.
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PMID:Australine, a pyrrolizidine alkaloid that inhibits amyloglucosidase and glycoprotein processing. 249 72

Maltase activity (EC 3.2.1.20) was solubilized from rabbit kidney brush-border membrane by using 1.0% Triton X-100 and purified 230-fold with an overall recovery of 30%. The purification procedure makes use of heat precipitation, chromatography on DE-52 DEAE-cellulose and gel filtration on Sephacryl S-300. Rabbit kidney brush border exhibited glucoamylase activity with a maltase/glucoamylase ratio of 1.5:1 to 2.0:1. During purification the maltase and glucoamylase activities behaved identically. The Mr of the complex is 590,000, and it appears to be composed of eight identical subunits linked by disulphide bridges.
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PMID:Neutral maltase/glucoamylase from rabbit renal cortex. 250 56


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