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 kinetic properties of a maltase-glucoamylase complex with a neutral pH optimum, purified to homogeneity from the brush borders of the rabbit small intestine, are described. It has a broad range of substrate specificity, hydrolysing di- and poly-saccharides with alpha-1,4 and alpha-1,6 linkages. The Km and Vmax, values of the enzyme for the various substrates were determined. Starch and maltose were its best substrates. The kinetics of hydrolysis of two synthetic linear maltosaccharides, namely maltotriose and maltopentaose, were studied. Mixed-substrate incubation studies revealed the presence of at least two interacting sites on the enzyme, and the data were further analysed by the use of a number of non-substrate inhibitors.
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PMID:Kinetic studies on glucoamylase of rabbit small intestine. 0 6

Production of glucoamylase and glycosyltransferase by Endomyces fibuliger was found to depend on sources of carbon and nitrogen nutrition. Starch at a concentration above 0.5% in the medium stimulated biosynthesis of glycosyltransferase but inhibited production of glucoamylase by End. fibuliger 20-9. The rate of growth of the micro-organism increased by a factor of 3.3 with an increase of starch concentration from 0.5 to 6%. Synthesis of glycosyltransferase was repressed by glucose, lactose, sucrose and maltose. Synthesis of glucoamylase was repressed by lactose, sorbose and galactose. Synthesis of glycosyltransferase was stimulated by xylose, sorbose and galactose. Production of glucoamylase was stimulated by xylose and arabinose. Growth of the culture and synthesis of glucoamylase and maltase in the cultural broth were stimulated by an increase in the concentration of maize extract. Biosynthesis of glucoamylase and glycosyltransferase was stimulated by NH4H2PO4.
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PMID:[Effect of growth medium composition of glucoamylase and glycosyltransferase activity of Endomyces fibuliger]. 1 49

Starch digestion and absorption is augmented appreciably by physical processing of grain or legume and by heating to 100 degrees C for several minutes before its ingestion. Starch, a polysaccharide composed of alpha 1,4-linked glucose units (amylose) and alpha 1,4-1,6-linked branched structure (amylopectin), is cleaved in the duodenal cavity by secreted pancreatic alpha-amylase to a disaccharide (maltose), trisaccharide (maltotriose), and branched alpha-dextrins. These final oligosaccharides are hydrolyzed efficiently by complimentary action of three integral brush border enzymes at the intestinal surface: glucoamylase (maltase-glucoamylase, amyloglucosidase), sucrase (maltase-sucrase) and alpha-dextrinase (isomaltase). The final monosaccharide glucose product is then cotransported into the enterocyte along with Na+ by a specific brush border 75-kDa transport protein in the rate-limiting step for overall starch assimilation. By virtue of this sequential luminal and membrane digestion followed by glucose transport, starch is assimilated in a very efficient manner in nonruminants.
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PMID:Starch digestion and absorption in nonruminants. 172 68

Epidemiological and experimental studies indicate a strong association between an elevated colon cancer risk and increased fecal excretion of secondary bile acids, neutral sterols, and prolonged gastrointestinal transit time. Starch malabsorption, on the other hand, has been reported to be a possible protective factor in colon carcinogenesis. To study the impact of starch malabsorption on these parameters, 12 healthy volunteers consumed a diet rich in starch for two 4-week periods. During a double-blind crossover trial they received the alpha-glucosidase inhibitor acarbose (BAY g 5421) in one of the study periods and placebo in the other. During acarbose treatment stool wet weight increased by 68%, stool dry weight by 57%, and gastrointestinal mean transit time by 30%. Fecal concentrations (mg/g dry weight) of the neutral sterols coprostanol, coprostanone, campesterol, 4-cholesten-3-one, and beta-sitosterol decreased by 36.8, 48.7, 42.1, 34.6, and 39.4%, respectively, under acarbose. Concentrations of the major secondary bile acids, deoxycholic and lithocholic acid, decreased by 59.9 and 52.2%, respectively. In spite of an increased stool weight, also daily excretion (mg/day) of these two bile acids was lower under acarbose (47.9 and 36.6%, respectively) compared to placebo, whereas excretion of the main primary bile acid, cholic acid, rose from 22.58 mg/day to 379.80 mg/day during the acarbose period. The changes in fecal bile acid and neutral sterol excretion found during acarbose treatment may explain a protective effect of starch malabsorption on colon cancer development.
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PMID:Effect of starch malabsorption on fecal bile acids and neutral sterols in humans: possible implications for colonic carcinogenesis. 186 44

Starch-degrading, amylolytic enzymes are widely distributed among microbes. Several activities are required to hydrolyze starch to its glucose units. These enzymes include alpha-amylase, beta-amylase, glucoamylase, alpha-glucosidase, pullulan-degrading enzymes, exoacting enzymes yielding alpha-type endproducts, and cyclodextrin glycosyltransferase. Properties of these enzymes vary and are somewhat linked to the environmental circumstances of the producing organisms. Features of the enzymes, their action patterns, physicochemical properties, occurrence, genetics, and results obtained from cloning of the genes are described. Among all the amylolytic enzymes, the genetics of alpha-amylase in Bacillus subtilis are best known. Alpha-Amylase production in B. subtilis is regulated by several genetic elements, many of which have synergistic effects. Genes encoding enzymes from all the amylolytic enzyme groups dealt with here have been cloned, and the sequences have been found to contain some highly conserved regions thought to be essential for their action and/or structure. Glucoamylase appears usually in several forms, which seem to be the results of a variety of mechanisms, including heterogeneous glycosylation, limited proteolysis, multiple modes of mRNA splicing, and the presence of several structural genes.
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PMID:Microbial amylolytic enzymes. 254 11

Starch is the main carbohydrate in the food of poultry. Starch granules are digested by pancreatic alpha-amylase in the small intestine. Intestinal villi have enterocytes that project microvilli with a fibrous glycocalyx from the surface. These fine structures are envisaged to entrap water that is mixed with mucin from nearby goblet cells to form the "unstirred water layer." Maltose, maltotriose and alpha-limit dextrins must diffuse across this first barrier to absorption to be hydrolyzed by maltase and sucrase-isomaltase immobilized at the membrane; however, the resultant glucose, once formed, accrues at the surface to provide a concentration advantage. Fowl adjust to changes in dietary starch by altering the amount of amylase released, intestinal surface area and enterocyte carbohydrase concentration. Enterocytes arising during embryonic development have no carbohydrases and are not involved with glucose absorption, but they appear to be specialized for maternal immunoglobin transfer in ovo. Embryonic villi are stimulated by transfer activity, and their growth depends on enterocytes arising from the crypt. Mature crypt cells are capable of digestion-absorptive activities and dominate the villus shortly after the chick hatches when yolk sac reserves are depleted.
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PMID:Digestion and absorption of carbohydrates in fowl and events through perinatal development. 258 3

The activity of enzymes releasing glucose and reducing sugars from sucrose, maltose, starch and dextran was compared in the same pooled samples of plaque fluid (PF) from 24 h human dental plaque. Equimolar amounts of glucose and fructose were released from sucrose in 3 h incubations. Reducing activity was released from sucrose or starch at a similar rate. The rate of glucose release from the starch substrate was similar to that from maltose but lower than that from sucrose. Raffinose was hydrolysed, indicating beta-fructosidase activity in PF. The hydrolysis of maltose, trehalose and melezitose confirmed the presence of alpha-glucosidase activity. Maltose was metabolized partially to a maltosaccharide. No dextranase activity was detectable in PF, and the soluble polymeric carbohydrate in PF was partially degraded by fungal dextranase. Starch was degraded to dextrins, maltose and glucose.
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PMID:Hydrolysis of some carbohydrate substrates by enzymes of pooled human dental plaque fluid. 617 18

Starch supported growth of continuous cultures of Bacteroides ovatus when this carbohydrate provided the sole source of carbon and energy. Inducible amylase and alpha-glucosidase activities were inversely related to dilution rate in starch-limited and starch-excess chemostats over the dilution rate (D) range D = 0.03/h to D =0.20/h, and were partly repressed during growth under conditions of starch-excess. Preparative isoelectric focusing of B. ovatus cytoplasmic extracts indicated the existence of three distinct starch-hydrolyzing enzymes. Incubation of active fractions from the isoelectric focusing cell with maltose and a variety of low-molecular-weight oligosaccharides (maltotriose, maltotetraose, maltopentaose, maltohexaose, maltoheptaose) identified a single amylase activity, an enzyme with combined beta-amylase and glucoamylase/alpha-glucosidase properties, and also a possible pullulanase. The ability of B. ovatus to synthesize several starch-hydrolyzing enzymes with different specificities and activities may confer a significant competitive advantage to this organism in the colonic ecosystem.
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PMID:Starch utilization by Bacteroides ovatus isolated from the human large intestine. 909 29

Alkaliphilic bacteria were isolated from soil and water samples obtained from Ethiopian soda lakes in the Rift Valley area--Lake Shala, Lake Abijata, and Lake Arenguadi. Starch-hydrolyzing isolates were selected on the basis of their activity on starch agar plate assay. Sixteen isolates were chosen, characterized, and subjected to 16S rRNA gene sequence analysis. All the isolates were gram positive and catalase- and beta-galactosidase positive. All isolates except one were motile endospore-forming rods and were found to be closely related to the Bacillus cluster, being grouped with Bacillus pseudofirmus, Bacillus cohnii, Bacillus vedderi, and Bacillus agaradhaerens. The one exception had nonmotile coccoid cells and was closely related to Nesterenkonia halobia. The majority of the isolates showed optimal growth at 37 degrees C and tolerated salinity up to 10% (w/v) NaCl. Both extracellular and cell-bound amylase activity was detected among the isolates. The amylase activity of two isolates, related to B. vedderi and B. cohnii, was stimulated by ethylenediaminetetraacetic acid (EDTA) and inhibited in the presence of calcium ions. Pullulanase activity was expressed by isolates grouped with B. vedderi and also most of the isolates clustered with B. cohnii; cyclodextrin glycosyltransferase was expressed by most of the B. agaradhaerens-related strains. Minor levels of alpha-glucosidase activity were detected in all the strains.
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PMID:Starch-hydrolyzing bacteria from Ethiopian soda lakes. 1135 57

Eight steers and 12 lambs were used in a completely randomized experimental design to determine the effect of partial alpha-amylase starch hydrolysate (SH) on small intestinal sodium-dependent glucose transport activity. Starch hydrolysate was delivered ruminally or abomasally to steers (960 g/day) and sheep (144 g/day) for 7 days. On day 7, the steers were rendered unconscious, exsanguinated and eviscerated. A 1-m section of jejunum was collected starting at the duodenojejunal flexure. Sheep were anaesthetized with pentobarbital and the second meter of small intestine (jejunum) was collected. Brush-border membrane vesicles were prepared and sodium-dependent glucose uptake activity was measured using the rapid uptake/filtration technique. Alkaline phosphatase and maltase activity was enriched by 8.2+/-0.5- and 8.4+/-1.2-fold in the vesicle preparation, respectively, and was not different between treatments. Abomasal SH increased (P=0.03) the Na/glucose co-transport approximately two-fold in both cattle (47.2-114.0+/-31.5 pmol/mgxsec) and sheep (77.4-152.0+/-25.7 pmol mg(-1) s(-1)). We conclude that Na/glucose co-transport activity by enterocytes responds to luminal alpha-linked glucose (from abomasal infusion) in ruminants, compared with controls. Intestinal maltase-specific activity does not respond to alpha-linked glucose in cattle, and decreases slightly in sheep.
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PMID:Influence of alpha-linked glucose on jejunal sodium-glucose co-transport activity in ruminants. 1142 27


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