Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.20 (alpha-glucosidase)
 4,237 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A highly thermostable alpha-glucosidase (E C.3.2.1.20) from an extreme thermophile, Thermus thermophilus HB 8, was purified to homogeneous by ammonium sulfate fractionation, DEAE-cellulose chromatography and preparative slab gel electrophoresis. The enzyme was purified 17 fold with 21% recovery of activity. The enzyme had a molecular weight of 67000 by SDS-PAGE. The isoelectric point was pH4.5 by IEF on PAG. The enzyme hydrolized p-nitrophenyl-alpha-glucoside (PN-PG), sucrose and maltose, but not cellobiose, melibiose and soluble starch. The km value for PNPG was 0.4mmol/L, the Vmax was 0.29 mumol.min-1.mg-1. The enzyme exhibited high thermostability. After incubation at 90 degrees C for 10 h in 50 mmol/L acetate buffer pH 5.8, the enzyme retained 90% of its original activity. The half-live (t1/2) at 95 degrees C was 108 min. The enzyme was activated by Mg2+, Mn2+, Ca2+, Ba2+ and strongly inhibited by Hg2+, Cu2+. Modification of the enzyme by EDC or DEPC led to complete loss of activity, which suggests that carboxyl group(s) and histidine residue(s) are essential for activity of alpha-glucosidase.
 ...
PMID:[Purification and characterization of alpha-glucosidase from an extreme thermophile, Thermus thermophilus HB 8]. 141 35

The definite structure and chemical stability of a new glucoside of L-ascorbic acid (AA) which was enzymatically glucosylated with rat intestinal and rice seed alpha-glucosidases were reported. The stability of this AA derivative in water under aerobic conditions was proved by its remarkable resistance against enhanced oxidative degradation by heat, Cu2+ ion or ascorbate oxidase, and it was found to have no reducing activity toward radicals. These properties were obviously distinguishable from those of AA. This glucoside was effectively hydrolyzed by alpha-glucosidases which possessed the ability to synthesize itself, resulting in the liberation of AA activity. The conjugate was composed of equimoles of AA and glucose. Nuclear magnetic resonance spectra, mass spectra, pH profiles of ultraviolet spectra and pK(a) value of 3.10 supported the coupling of alpha-glucose to the 2-position of AA. From these results, its structure was assigned 2-O-alpha-D-glucopyranosyl-L-ascorbic acid, being distinct from 6-O-alpha-D-glucopyranosyl-L-ascorbic acid formed with Aspergillus niger alpha-glucosidase. These findings indicate that the 2-O-glucoside formed by regioselective transglucosylation withstands oxidative degradation even in aqueous solutions and it can be used as an available active AA source for multicomponent liquid products.
 ...
PMID:L-ascorbic acid alpha-glucoside formed by regioselective transglucosylation with rat intestinal and rice seed alpha-glucosidases: its improved stability and structure determination. 208 81

Disaccharidases of oral bacteria, especially alpha-glucosidase and beta-fructofuranosidase, are considered to play an important role in the induction of dental caries. Upon the examination of disaccharidases from several strains of saccharolytic oral bacteria, we found all of those bacteria to be capable of hydrolyzing the glycosidic linkage of sucrose. One species of bacteria, Rothia dentocariosa, was found to contain a single disaccharidase, alpha-glucosidase. This enzyme was partially purified by ammonium sulfate precipitation, gel filtration and ion-exchange column chromatography. The optimum pH and temperature for the enzyme activity was found to be 6.8-7.0 and 40 degrees C, respectively. The enzyme activity was strongly inhibited by Ag+, Hg2+, Cu2+, Fe2+ and Tris (Hydroxymethyl) aminomethane.
 ...
PMID:Partial purification and characterization of alpha-glucosidase from Rothia dentocariosa. 263 58

Activities of the enzymes lactase, sucrase, maltase, alkaline phosphatase, and superoxide dismutase (SOD) were measured in mucosa of duodenum and ileum of the rat after 70% resection of mid-small intestine or sham operation (transection). We also measured the concentrations of zinc, copper, and manganese in several tissues to assess trace metal homeostasis postresection. Resection resulted in decreased specific activities of disaccharidases and alkaline phosphatase in duodenum, while specific activities remained unchanged in ileum. Specific activity of total SOD (the sum of Cu-Zn and Mn SOD) and Mn SOD was the same in duodenum after resection but was markedly increased in ileum. Tissue trace metal concentrations changed minimally. Because of postresection mucosal growth, total segmental activity of disaccharidases and alkaline phosphatase was the same in duodenum and increased in ileum of resected compared to transected rats. Segmental activity of total SOD and Mn SOD doubled in duodenum and trebled in ileum of resected as compared to transected rats. Thus, total segmental enzyme activity is maintained or increased postresection by increased enterocyte proliferation rate and mucosal growth.
 ...
PMID:Adaptation of the duodenum and ileum of the rat to mid-gut resection: enzyme activity and trace metal status. 308 Aug 64

In an attempt to elucidate the effect of metallic ions and EDTA on acidic alpha-D-glucosidase activity, we measured acidic alpha-D-glucosidase activity from either lymphocyte and muscle tissue homogenates or intact cells after incubation with metallic ions. The results showed that this enzyme activity was strongly inhibited by Ag+, Hg2+, and Fe3+ in either lymphocyte or muscle tissue homogenates. There was no effect of Zn2+, Cu2+, and Cd2+. However, intact cells, either lymphocyte or muscle cells, after incubation with Zn2+ for 1 or 2 hr, showed enhanced enzyme activity and suppression in the other metallic ion groups, especially in Ag+, Hg2+, and Fe3+. Since deficiency of this enzyme can cause type II glycogen storage disease (Pompe's disease), the more we understand the character of this enzyme, the more we can improve our enzymatic therapy.
 ...
PMID:Zinc can activate cellular acidic alpha-D-glucosidase activity. 314 35

Intestinal adaptation has been studied in rats with pancreatic atrophy induced by feeding a copper-deficient diet and penicillamine and in rats with carbohydrate maldigestion induced by feeding of an alpha-glucosidase inhibitor (acarbose). Pancreatic atrophy led to a significant increase of weight, protein, and DNA content as well as specific activities and total amounts of the enzymes sucrase and maltase in the distal but not in the proximal part of the small intestine. Plasma levels of CCK and GIP were significantly higher in rats with pancreatic atrophy, whereas plasma levels of gastrin and insulin were lower. Tissue concentrations of gastrin in the antrum and GIP in duodenum and jejunum were unchanged. Duodenal CCK and jejunal substance P, somatostatin, and VIP and ileal substance P and somatostatin were significantly decreased in rats with acinar atrophy. Glucosidase inhibition by acarbose feeding led to weight increase of the small intestine and cecum. This was more marked when acarbose was fed together with a fiber-free diet. Under these conditions the protein and DNA content also increased significantly in both gut segments and maltase and sucrase content predominantly in the distal part. Insulin plasma concentration decreased significantly in the acarbose-fed groups, whereas GIP, gastrin, and CCK plasma concentrations remained unchanged. After fiber-rich diet tissue concentrations of gastrin in the antrum and insulin in the pancreas were significantly higher and GIP concentrations in the duodenum and jejunum significantly lower than after fiber-free diet. Acarbose increased the pancreatic insulin concentration only in the fiber-free group and did not influence gastrin and GIP concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Adaptation of the small intestine to induced maldigestion in rats. Experimental pancreatic atrophy and acarbose feeding. 389 54

Lactobacillus acidophilus IFO 3532 was found to produce only intracellular alpha-glucosidase (alpha-D-glucoside glucohydrolase; EC 3.2.1.20). Maximum enzyme production was obtained in a medium containing 2% maltose as inducer at 37 degrees C and at an initial pH of 6.5. The enzyme was formed in the cytoplasm and accumulated as a large pool during the logarithmic growth phase. Enzyme production was strongly inhibited by 4 microM CuSO4, 40 microM CoCl2, and beef extract; MnSO4 and the presence of proteose peptone and yeast extract in the medium greatly enhanced enzyme production. A 16.6-fold purification of alpha-glucosidase was achieved by (NH4)2SO4 fractionation and DEAE-cellulose column chromatography. The enzyme showed high specificity for maltose. The Km for alpha-p-nitrophenyl-beta-D-glucopyranoside was 11.5 mM, and the Vmax for alpha-p-nitrophenyl-beta-D-glucopyranoside hydrolysis was 12.99 mumol/min per mg of protein. The optimal pH and temperature for enzyme activity were 5.0 and 37 degrees C, respectively. The enzyme activity was inhibited by Hg2+, Cu2+, Ni2+, Zn2+, Ca2+, Co2+, urea, rose bengal, and 2-iodoacetamide, whereas Mn2+, Mg2+, L-cysteine, L-histidine, Tris, and EDTA stimulated enzyme activity. Transglucosylase activity was present in the partially purified enzyme, and isomaltose was the only glucosyltransferase product. Amylase activity in the purified preparation was relatively weak, and no isomaltase activity was detected.
 ...
PMID:Production and properties of alpha-glucosidase from Lactobacillus acidophilus. 641 77

1-deoxynojirimycin (DNJ), a 5-imino analog of 1-deoxyglucose, is a potent inhibitor of alpha-glucosidase 1. DNJ and its derivatives have been considered as experimental drugs against human HIV-1 and hepatitis B viruses. Since amino and imino ligands have a high affinity for copper, it seems possible that biological activity of DNJ may be, at least in part, modulated by tissue copper. To test this possibility, potentiometric and spectroscopic studies of the complexation of DNJ by cupric ions were performed in order to obtain thermodynamic and structural background for further pharmacologic investigations. The effect of histidine, a major tissue copper carrier, on coordination equilibria was also studied. Results indicate that DNJ and Cu(II) form two stable complexes at physiological pH, CuH-1(DNJ)2+ and CuH-2(DNJ)2, involving Cu(II) chelation by the N-5 and O-6 donor atoms. In the presence of histidine, ternary complexes are also formed, of which the CuDNJHis+ species is stable in the physiological pH range. Binary Cu(II)-DNJ complexes are extremely effective mediators of in vitro oxidation of the guanine moiety in both 2'-deoxyguanosine (dG) and DNA to 8-oxoguanine (8-oxo-dG) and of DNA double strand scission by ambient O2 or H2O2. This mediation is suppressed by histidine in dG, but not in DNA. The results suggest that tissue Cu(II) may greatly enhance nonspecific cytotoxic effects of systemically administered DNJ through oxidative damage mechanisms, and therefore the prospective use of DNJ for therapeutic purposes must be developed with caution. On the other hand, however, the expected high genotoxic potential of synthetic Cu(II)-DNJ complexes may be used against viruses by means of targeted delivery of these complexes to the infected cells.
 ...
PMID:Copper(II) interactions with an experimental antiviral agent, I-deoxynojirimycin, and oxygen activation by resulting complexes. 891 12

A novel alpha-glucosidase with an apparent subunit mass of 59 +/- 0. 5 kDa was purified from protein extracts of Rhizobium sp. strain USDA 4280, a nodulating strain of black locust (Robinia pseudoacacia L), and characterized. After purification to homogeneity (475-fold; yield, 18%) by ammonium sulfate precipitation, cation-exchange chromatography, hydrophobic chromatography, dye chromatography, and gel filtration, this enzyme had a pI of 4.75 +/- 0.05. The enzyme activity was optimal at pH 6.0 to 6.5 and 35 degrees C. The activity increased in the presence of NH4+ and K+ ions but was inhibited by Cu2+, Ag+, Hg+, and Fe2+ ions and by various phenyl, phenol, and flavonoid derivatives. Native enzyme activity was revealed by native gel electrophoresis and isoelectrofocusing-polyacrylamide gel electrophoresis with fluorescence detection in which 4-methylumbelliferyl alpha-glucoside was the fluorogenic substrate. The enzyme was more active with alpha-glucosides substituted with aromatic aglycones than with oligosaccharides. This alpha-glucosidase exhibited Michaelis-Menten kinetics with 4-methylumbelliferyl alpha-D-glucopyranoside (Km, 0.141 microM; Vmax, 6.79 micromol min-1 mg-1) and with p-nitrophenyl alpha-D-glucopyranoside (Km, 0.037 microM; Vmax, 2.92 micromol min-1 mg-1). Maltose, trehalose, and sucrose were also hydrolyzed by this enzyme.
 ...
PMID:Purification and characterization of an alpha-glucosidase from Rhizobium sp. (Robinia pseudoacacia L.) strain USDA 4280. 1038 82

Tyrosinase is the key enzyme of melanin biosynthesis. It is a multiply glycosylated metalloenzyme, which has a long maturation time making it an ideal in vivo model system to probe protein folding and metal loading events. The use of NB-DNJ, an alpha-glucosidase I and II inhibitor has allowed us to dissect these processes. Here we show that tyrosinase folds through several inactive intermediates, at least two of which are recognised by the ER chaperone, calnexin. If the association with calnexin is prevented, more rapid folding occurs, the resulting protein fails to bind copper and is inactive. If dissociation from calnexin is inhibited, folding is prevented; the protein does not go through the normal secretory pathway and is targeted for degradation. Thus, tyrosinase folds off calnexin, giving alpha-glucosidase II a critical role, but the association with calnexin is essential to promote the correct folding which enables it to acquire copper.
 ...
PMID:Tyrosinase folding and copper loading in vivo: a crucial role for calnexin and alpha-glucosidase II. 1044 92


1 2 Next >>