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)

Toluene-treated cells of Streptococcus bovis JB1 phosphorylated cellobiose, glucose, maltose, and sucrose by the phosphoenolpyruvate-dependent phosphotransferase system. Glucose phosphorylation was constitutive, while all three disaccharide systems were inducible. Competition experiments indicated that separate phosphotransferase systems (enzymes II) existed for glucose, maltose, and sucrose. [14C]maltose transport was inhibited by excess (10 mM) glucose and to a lesser extent by sucrose (90 and 46%, respectively). [14C]glucose and [14C]sucrose transports were not inhibited by an excess of maltose. Since [14C]maltose phosphorylation in triethanolamine buffer was increased 160-fold as the concentration of Pi was increased from 0 to 100 mM, a maltose phosphorylase (Km for Pi, 9.5 mM) was present, and this activity was inducible. Maltose was also hydrolyzed by an inducible maltase. Glucose 1-phosphate arising from the maltose phosphorylase was metabolized by a constitutive phosphoglucomutase that was specific for alpha-glucose 1-phosphate (Km, 0.8 mM). Only sucrose-grown cells possessed sucrose hydrolase activity (Km, 3.1 mM), and this activity was much lower than the sucrose phosphotransferase system and sucrose-phosphate hydrolase activities.
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PMID:Transport and phosphorylation of disaccharides by the ruminal bacterium Streptococcus bovis. 282 69

Intracellular transport of two lysosomal enzymes, acid alpha-glucosidase and beta-hexosaminidase, was analyzed in human fibroblasts. The precursors of beta-hexosaminidase in normal fibroblasts were released from the membrane fraction by treatment with mannose 6-phosphate, but the precursor of alpha-glucosidase was not. Percoll density gradient centrifugation revealed a normal amount of acid alpha-glucosidase activity in heavy lysosomes in I-cell disease fibroblasts despite impaired maturation and defective phosphorylation, and beta-hexosaminidase activity was markedly reduced in lysosomes. It was concluded that the membrane-bound precursor of acid alpha-glucosidase is transported to lysosomes by a phosphomannosyl receptor-independent system although the enzyme lacks the recognition marker for the phosphomannosyl receptor and processing of an intermediate form to mature forms does not occur in this disease.
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PMID:Intracellular transport of acid alpha-glucosidase in human fibroblasts: evidence for involvement of phosphomannosyl receptor-independent system. 284 24

Yeast strains bearing a deficiency in trehalose-6-phosphate synthase activity are unable to accumulate trehalose on any carbon source unless they contain one of the MAL genes. If the gene is inducible then synthesis of trehalose occurs specifically during growth on maltose: when the MAL gene is constitutive then trehalose accumulation can also be seen when cells are grown on glucose. Different systems for trehalose synthesis were suggested: one of them would require the UDPG-linked trehalose synthase whereas the second would utilize an alternative pathway. We proposed a mechanism by which the gene-product of a MAL gene would serve as a common positive regulator for the expression of the genes coding for maltose permease, alpha-glucosidase and some component of the trehalose accumulation system. In order to elucidate this novel pathway a strain lacking UDPG-linked trehalose synthase activity and harboring a defect in maltose uptake was constructed. Excessive maltose uptake resulted in accumulation of intracellular maltose, and twice as much trehalose as in a control strain. Partial inhibition of hexokinase by xylose affected the ratio between internal maltose and trehalose and significantly reduced glycogen synthesis. Sodium fluoride also blocked glycogen synthesis but allowed for trehalose accumulation. Moreover, a mutant which lacks hexokinase I and II was unable to accumulate trehalose when grown on glucose in spite of the presence of a constitutive MAL2 gene. These results suggest that trehalose synthesis would require G-6-P formation derived from maltose. Such a deviation would allow for slowing down the glycolytic flux which, in turn, would favour efficient maltose utilization.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Further evidence for the alternative pathway of trehalose synthesis linked to maltose utilization in Saccharomyces. 344 33

We describe a method for measuring the catalytic activity of alpha-amylase (EC 3.2.1.1) in serum and urine, by use of a defined substrate: 1,4-alpha, D-4-nitrophenyl maltoheptaoside. We use a phosphate buffer of pH 7.10, containing chloride as activator and alpha-glucosidase (EC 3.2.1.20) as the auxiliary enzyme. After a lag phase of 4 min at 25 degrees C or 30 degrees C, or 3 min at 37 degrees C, the increase of absorption of 4-nitrophenol is measured at 410 nm or 405 nm. The pH value of the assay mixture is a compromise between optimum pH for the alpha-amylase reaction, shortest possible lag phase, and an acceptable absorptivity of 4-nitrophenol. Because the dissociation of 4-nitrophenol depends strongly on pH and temperature, we determined its absorptivity with various combinations of these variables in the assay. Heparin-treated plasma can be used, but not EDTA, fluoride, or citrate. Lipemia, hemoglobin less than or equal to mumol/L, bilirubin less than or equal to 170 mumol/L, glucose less than or equal to 100 mmol/L, and ascorbic acid less than or equal to 1 mmol/L of sample do not interfere in the assay.
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PMID:Optimized conditions for determining activity concentration of alpha-amylase in serum, with 1,4-alpha-D-4-nitrophenylmaltoheptaoside as substrate. 387 Nov 78

The molecular basis for charge heterogeneity in human hepatic alpha-glucosidase (alpha-D-glucoside glucohydrolase, EC 3.2.1.20) was determined by analysis of the carbohydrate and polypeptide components of the enzyme. Only small remnants of high mannose chains that contained neither sialic acid nor mannose 6-phosphate were detected in the carbohydrate structure. Four enzymatically active forms of alpha-glucosidase separated by chromatofocusing were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and were found to contain different polypeptides. The absence of charged residues in oligosaccharide chains and variability in the polypeptide subunits of the charge forms of hepatic alpha-glucosidase suggest that charge heterogeneity results from differences in the protein structure of the charge forms. The pattern of differences in the polypeptide subunits suggests that the charge forms for hepatic alpha-glucosidase may be the product of proteolysis.
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PMID:The molecular basis for charge heterogeneity in human acid alpha-glucosidase. 388 74

Glucose-1-phosphate-negative mutants that are unable to grow in a synthetic medium containing glucose-1-phosphate (G-1-P) as a sole carbon source were isolated by treatment of Agrobacterium tumefaciens IAM 1525 with N-methyl-N'-nitro-N-nitrosoguanidine. All of the enzymes involved in G-1-P metabolism (glucoside-3-dehydrogenase, 3-ketoglucose-1-phosphate-degrading enzyme, alpha-glucosidase, and phosphatases) were detected in the sonic extract prepared from resting cells of one of the mutants, strain M-24, in approximately equal levels to those in the parent strain. Resting cells of the mutant oxidized G-1-P to 3-ketoglucose-1-phosphate (3KG-1-P), the first product in G-1-P metabolism by the bacterium, with little subsequent degradation, whereas the parent showed further degradation of G-1-P via 3KG-1-P. Glucoside-3-dehydrogenase catalyzing 3-ketoglucoside formation was readily released from cells by osmotic shock, whereas the 3KG-1-P-degrading enzyme was not released. Thus, the former and the latter enzymes might be at different intracellular loci, such as periplasm and cytoplasm, respectively. It is suggested that the mutant strain M-24 is a G-1-P-negative mutant deficient in a 3KG-1-P transport system located on the cytoplasmic membrane.
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PMID:Glucose-1-phosphate-negative mutant of Agrobacterium tumefaciens. 469 Sep 62

The synthesis of the glycoprotein enzymes, invertase and acid phosphatase, by protoplasts of Saccharomyces mutant 1016, is inhibited by 2-deoxy-d-glucose (2-dG) after a 20- to 30-min lag period under conditions (external sugar to 2-dG ratio of 40:1) which cause only a slight decrease in total protein synthesis. Formation of one intracellular enzyme, alpha-glucosidase, is also sensitive, but production of another, alkaline phosphatase, is unaffected. A nonmetabolized glucose analogue, 6-deoxy-d-glucose, had no inhibitory effect. The total uptake of external fructose and maltose was decreased by 2-dG after a lag period of about the same duration as that before the inhibition of synthesis of enzymes or of mannan and glucan; during this time 2-dG was taken up by the protoplasts and accumulated primarily as 2-dG-6-phosphate (2-dG-6-P). Studies in vitro showed that 2-dG-6-P inhibits both yeast phosphoglucose isomerase and phosphomannose isomerase. The intracellular levels of the 6-phosphates of glucose, fructose, and mannose did not increase in the presence of 2-dG. We suggest that the high internal level of 2-dG-6-P blocks synthesis of the cell wall polysaccharides and glycoproteins in two ways. It directly inhibits the conversion of fructose-6-P to glucose-6-P and to mannose-6-P. At the same time, it restricts the transport of fructose and maltose into the cell; however, the continuing limited uptake of the sugars still provides sufficient energy for protein synthesis. The cessation of alpha-glucosidase synthesis is probably a result of depletion of the internal pool of maltose (the inducer). Our findings support the suggestion that restriction of synthesis of the carbohydrate moiety of glycoproteins reduces formation of the active enzyme.
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PMID:Inhibition by 2-deoxy-D-glucose of synthesis of glycoprotein enzymes by protoplasts of Saccharomyces: relation to inhibition of sugar uptake and metabolism. 505 66

In the course of screening amylase inhibitor producing, microorganisms, a strain identified as Streptomyces nigrifaciens NTU-3314 was found to have the highest inhibitor-producing ability among the other isolated strains. This strain was aerobically cultured at 30 degrees C in a 5l jar fermentor with a working volume of 2l. The optimum cultural medium consisted of defatted soybean flake 3.0%, potato starch 4.0%, casein 0.6%, sucrose 0.6%, serine 0.02% and NaCl 0.8% (pH 7.0). With an aeration rate of 1.5 vvm, an agitation speed of 300 rpm and an inoculum of 15% seed (previously grown in seed medium 3), the highest amount of inhibitor was obtained after 24 hours of cultivation. The amylase inhibitor produced had inhibitory effects on both alpha-amylase and glucoamylase, but not on beta-amylase, alpha-glucosidase, beta-glucosidase or dextranase. It was quite stable in 0.1M phosphate buffer (pH 7.0) and nearly 100% of its activity was retained even after boiling at 100 degrees C for 20 min.
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PMID:The microbial production of amylase inhibitor and its application. I. Isolation and cultivation of Streptomyces nigrifaciens NTU-3314. 608 1

In the pigeon, 70-80% of the activities of maltase (alpha-D-glucoside glucohydrolase EC 3.2.1.20), sucrase (alpha-glucohydrolase, EC 3.2.1.48), isomaltase (dextran 6-alpha-D-glucan hydrolase, EC 3.2.1.10) and glucoamylase (1,4-alpha-D-glucan glucohydrolase, EC 3.2.1.3) were found to be localized in the brush-border membrane of intestinal epithelial cells. Of the total glycosidase activities in the mucosal homogenate, nearly 60 to 70% were recovered in the microsomal (105 000 X g) fraction, about 30% in the mitochondrial (22 000 X g) fraction and less than 5% from the cytosol (105 000 X g supernatant) fraction. The hydrolases were solubilized by digestion with papain but not with trypsin, and the phosphate ion had a protective effect in the solubilization. Amongst detergents, Triton X-100 but not sodium deoxycholate, was found to truly solubilize these enzymes.
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PMID:Studies on the intestinal disaccharidases of the pigeon. II. Subcellular localization and solubilization. 618 28

Most biological fluids contain both neutral and acid alpha-glucosidase. Optimal conditions were therefore developed for the selective determination of the activity of neutral and acid alpha-glucosidase, using 2-step, discontinuous assays. In the first step of the assay of neutral alpha-glucosidase, glucose was liberated from maltose (citrate-phosphate buffer, pH 6.8, 20 mmol/l maltose, 25 mmol/l turanose). Under these incubation conditions, turanose inhibited the residual activity of acid alpha-glucosidase almost completely without influencing the activity of neutral alpha-glucosidase. In the first step of the acid alpha-glucosidase assay, glucose was liberated from maltose (citrate-phosphate buffer, pH 3.8, 50 mmol/l maltose, 2 mol/l potassium chloride). Under these incubation conditions, potassium ions stimulate the activity of acid alpha-glucosidase and simultaneously inhibit almost completely the residual activity of neutral alpha-glucosidase. In the second step of the assay of neutral and acid alpha-glucosidase, the liberated glucose was measured by hexokinase/glucose-6-phosphate dehydrogenase. The effect of turanose and potassium ions on neutral and acid alpha-glucosidase from human urine was characterized.
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PMID:Selective determination of the activities of neutral and acid alpha-glucosidase using discontinuous assays. 635 65


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