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At least 19 recordsLinked to original sources
PubMed1989

Inhibition by maltose, isomaltose, and nigerose of the synthesis of high-molecular-weight D-glucans by the D-glucosyltransferases of Streptococcus sobrinus.

Two D-glucosyltransferases are produced by Streptococcus sobrinus C211. One (GTF-S) catalyzes the conversion of sucrose into soluble alpha-(1----6)-linked alpha-(1----3)-branched D-glucans, and the other (GTF-I), of sucrose into alpha-(1----3)-linked alpha-(1----6)-branched D-glucans. These enzymes were studied by using maltose, isomaltose, and nigerose as inhibitors. Maltose and isomaltose were found to be competitive inhibitors of GTF-S, whereas nigerose has no effect on GTF-S activity. The Ki values for maltose and isomaltose were determined to be 11 and 15mM, respectively. Maltose, isomaltose, and nigerose competitively inhibit GTF-I. The Ki values for these inhibitors were found to be approximately 0.8, 2.5, and 15mM, respectively. The inhibitory properties of each disaccharide are interpreted in terms of conformational comparisons with sucrose.

Carbohydrate Conformation↗
PubMed1990

Binding of isomaltose and maltose to the glucoamylase from Aspergillus niger, as studied by fluorescence spectrophotometry and steady-state kinetics.

The binding of maltose, isomaltose, and D-glucono-1,5-lactone to the glucoamylase [E.C.3.2.1.3] from Aspergillus niger was monitored by the fluorescence-intensity change (delta F) based on the tryptophan residues of the enzyme, and the binding parameters (Kd and delta Fmax) were evaluated from the dependence of delta F on the concentration of substrate and analogue. Maltose caused the fluorescence-intensity change, but isomaltose did not, although it is hydrolyzed by the enzyme. Both substrates bind to the glucoamylase of Rhizopus niveus and cause delta F, suggesting that some difference exists in the conformation of the isomaltose-binding subsites between the two glucoamylases.

Aspergillus niger↗
PubMed1989

Thermodynamics of hydrolysis of disaccharides. Cellobiose, gentiobiose, isomaltose, and maltose.

The thermodynamics of the enzymatic hydrolysis of cellobiose, gentiobiose, isomaltose, and maltose have been studied using both high pressure liquid chromatography and microcalorimetry. The hydrolysis reactions were carried out in aqueous sodium acetate buffer at a pH of 5.65 and over the temperature range of 286 to 316 K using the enzymes beta-glucosidase, isomaltase, and maltase. The thermodynamic parameters obtained for the hydrolysis reactions, disaccharide(aq) + H2O(liq) = 2 glucose(aq), at 298.15 K are: K greater than or equal to 155, delta G0 less than or equal to -12.5 kJ mol-1, and delta H0 = -2.43 +/- 0.31 kJ mol-1 for cellobiose; K = 17.9 +/- 0.7, delta G0 = -7.15 +/- 0.10 kJ mol-1 and delta H0 = 2.26 +/- 0.48 kJ mol-1 for gentiobiose; K = 17.25 +/- 0.7, delta G0 = -7.06 +/- 0.10 kJ mol-1, and delta H0 = 5.86 +/- 0.54 kJ mol-1 for isomaltose; and K greater than or equal to 513, delta G0 less than or equal to -15.5 kJ mol-1, and delta H0 = -4.02 +/- 0.15 kJ mol-1 for maltose. The standard state is the hypothetical ideal solution of unit molality. Due to enzymatic inhibition by glucose, it was not possible to obtain reliable values for the equilibrium constants for the hydrolysis of either cellobiose or maltose. The entropy changes for the hydrolysis reactions are in the range 32 to 43 J mol-1 K-1; the heat capacity changes are approximately equal to zero J mol-1 K-1. Additional pathways for calculating thermodynamic parameters for these hydrolysis reactions are discussed.

Calorimetry↗
PubMed1989

[Current diagnostic method for saccharose-isomaltose malabsorption].

The authors present the cases of 4 children who suffered from saccharose-isomaltose malabsorption. The clinical symptoms developed following artificial feeding. The diagnosis was made by the histological examination of small intestine samples and with the simultaneous measurement of disaccharide enzyme activity. The histological picture and activity of lactase enzyme were practically normal. The saccharose H2 breath test gave only in 1 case positive result. The treatment of the children required saccharose-free diet. The tolerance showed no improvement during the treatment.

Child, Preschool↗
PubMed1979

Binding constants of NZB myeloma antidextrans for dextrans and isomaltose oligosaccharides determined by affinity electrophoresis.

Association constants of dextrans (Ka) and oligosaccharides (Kia) from NZB myeloma antidextrans (PC3858 and PC3936) were studied by affinity electrophoresis. With linear dextrans or with those with a low degree of branching, Ka ranged from 2.7 X 10(3) to 5.4 X 10(4) ml/g for PC3858 and from 1.3 X 10(4) to 2.6 X 10(5) ml/g for PC3936. Completely linear alpha-(1 leads to 6)-linked dextrans, LD7 and D3, showed relatively high affinities for the two NZB antidextrans. With oligosaccharides, the Kia value increased as the number oa alpha-(1 leads to 6)-linked glycosyl residues increased. Isomaltoheptaose (IM7) showed the highest Kia (1.9 X 10(4) M-1 for PC3858 and 1.63 X 10(4) M-1 for PC3936), whereas isomaltose (IM2) had the lowest Kia (2.36 X 10(2)M-1 for PC3858 and 1.32 X 10(2)M-1 for PC3936). Pullulan and glycogen showed very weak affinity for PC3936, but they did not react at all with PC3858. These findings indicate that NZB myeloma antidextrans, PC3858 and PC3936, are specific for internal chains of alpha-(1 leads to 6)-linked dextrans. Data on the precision with which Ka and Kia can be determined are presented.

Animals↗
PubMed1990

[Primary saccharose-isomaltose deficit: a 20-year case load].

In the last twenty years we have diagnosed 9 cases of congenital sucrase-isomaltase deficiency. In all the cases the diagnosis was made before 9 months of age and was confirmed by quantitative determination of sucrase-isomaltase activity in jejunal mucosal homogenates. Malnutrition and dehydration were frequent findings. In 3 cases there was clinical intolerance to dextrinomaltose and to glucose polymers. In the 6 cases in which were performed, abnormal breath H2 test after an oral sucrose load was found. Lactase activity was above the mean in all cases and an important decrease of maltase activity was demonstrated. The enzymatic deficiency persisted even though the clinical tolerance to sucrase improved with age.

Carbohydrate Metabolism, Inborn Errors↗
PubMed1992

Stopped-flow fluorescence and steady-state kinetic studies of ligand-binding reactions of glucoamylase from Aspergillus niger.

The presteady-state and steady-state kinetics of the binding and hydrolysis of substrates, maltose and isomaltose, and the transition-state analogue, gluconolactone, by glucoamylase from Aspergillus niger were investigated using initial-rate, stopped-flow and steady-state methods. The change in the intrinsic fluorescence of the enzyme was monitored. Distinct mechanistic differences were observed in the interaction of the enzyme with maltose compared to isomaltose. Hydrolysis of maltose requires a three-step mechanism, whereas that of isomaltose involves at least one additional step. The rates of an observed conformational change, which is the second discernible step of the reactions, clearly show a tighter binding of maltose compared to isomaltose, probably because the reverse rate constants differ. Compared to the non-enzymic hydrolysis the transition-state stabilization energy of glucoamylase is approximately -66 kJ/mol with maltose and only -14 kJ/mol with isomaltose. Kinetic analysis of the binding of the inhibitor, gluconolactone, implies that independent interactions of two molecules occur. One of these, apparently, is a simple, fast association reaction in which gluconolactone is weakly bound. The other resembles binding of maltose, involving a fast association followed by a conformational change. Based on the results obtained, we propose new reaction mechanisms for Aspergillus glucoamylase.

Aspergillus niger↗
PubMed1975

The specificity of the synthetic reaction of two yeast alpha-glucosidases.

The specificity of the hydrolytic reaction has been compared to that of the synthetic reaction for maltase and isomaltase (alpha-methyl-D-glucosidase) from Saccharomyces oviformis. Maltase which hydrolyzes the alpha-1,4-disaccharide, maltose, and the alpha-1,6-disaccharide, isomaltose, catalyzes the formation of both maltose and isomaltose from free glucose. Isomaltase, which hydrolyzes isomaltose but not maltose, catalyzes the formation only of isomaltose from glucose. Both enzymes hydrolyze p-nitrophenyl-alpha-D-glucoside releasing the alpha-anomer of glucose. The enzymes utilize the alpha-anomer but not the beta-anomer for the synthesis of the disaccharides. These results are consistent with the double displacement mechanism for glycosidases and with the proposal that the glucosyl-enzyme complex is an intermediate in the reaction. The competitive inhibition by D-glucose is independent of its anomeric form for both enzymes.

Borohydrides↗
PubMed1990

Purification and properties of an oligo-1,6-D-glucosidase from an alkalophilic Bacillus species.

An isomaltose-hydrolyzing alpha-D-glucosidase from the alkalophilic Bacillus designated strain F5 was purified to an electrophoretically homogeneous state. The molecular weight of the purified glucosidase was 60,000 by SDS-poly(acrylamide) gel electrophoresis, and 63,000 by Sephacryl S-200 gel-filtration chromatography. The enzyme was most active for isomaltose at pH 6.0-6.5 and 45 degrees, and stable up to 50 degrees at pH 7.0 and in the range of pH 6.0-9.0 at 50 degrees by 10-min incubation. The apparent Vmax and Km values for isomaltose were 34.5 mumol.min-1.mg-1 of protein, and 3.33 mM. Panose and isomaltotriose are the best substrates for this enzyme. The restricted substrate specificity indicated the assignment of the enzyme to be an oligo-1,6-glucosidase (dextrin 6-alpha-glucanohydrolase; EC 3.2.1.10), but it was suggested that it could be a new type of oligo-1,6-glucosidase on the basis of its action on a series of (1----4)-alpha-malto-oligosaccharides.

Bacillus↗
PubMed1990

Leucocyte alpha-1,4- and alpha-1,6-glucosidase activities towards oligosaccharides in late onset glycogenosis type II.

We describe the partial characterization and some properties of leucocyte alpha-glucosidase towards disaccharides with the alpha-1,4 (maltose) and alpha-1,6-glucosidic linkage (isomaltose) and tetrasaccharides with the alpha-1,4 (maltotetraose) and alpha-1,6-glucosidic linkage (tetrasaccharide, Glc alpha 1----6Glc alpha 1----4Glc alpha 1----4Glc, which was isolated from the urine of a patient with glycogenosis type II). Leucocyte alpha-glucosidase showed optimal activity towards all four oligosaccharides under two conditions, acidic (pH 4.0-4.5) and neutral (pH 6.0-6.5) regions. Our comparative studies on enzyme kinetics showed that leucocyte alpha-glucosidase was able to hydrolyze both the 1----4 isomers and the 1---6 isomers at acidic and neutral pH. Acid alpha-glucosidase could hydrolyze maltose about 10 times faster than isomaltose, and maltotetraose about 5 times faster than tetrasaccharide isolated from urine. In leucocytes of the patient with late onset glycogenosis type II, acid alpha-glucosidase activities towards maltose, isomaltose, maltotetraose and tetrasaccharide isolated from urine showed 75.3%, 67.4%, 76.5% and 41.4% of normal control values, respectively. Neutral alpha-glucosidase activities towards these four oligosaccharides were normal. Tetrasaccharide with alpha-1,6-glucosidic linkage might be accumulated by the impaired hydrolysis in the circulation as well as the leakage of undegraded glycogen to the circulation from the affected muscle.

Adult↗
PubMed1977

[Characterization of dextranase from Penicillium purpurogenum (Ftoll)].

An extracellular dextranase (E. C. 3.2.1.11) was purified from cell-free culture filtrates of Penicillium purpurogenum (Ftoll). The enzyme was most active at pH 5,5. The dextranase was endo-type, it split quickly isomaltotetraose into two isomaltose molecules, slowly degraded isomaltotriose, and did not act on isomaltose. The rate of isomaltooligosaccharides hydrolysis was increased with the increase of the polymerization degree. Polyols obtained from isomaltooligosaccharides were split more slowly than the respective sugars. The isomaltopentaitol was split at two glucosidic linkages, 38% of hydrolyzed linkages being the second linkage from the sorbitol end of the molecule and 62% being the third one. The degree of degradation of dextrans depended on amount of 1,6 linkages. Isomaltose and tetrasaccharides of two types, 2(2)-alpha-D-glucosylmaltotriose and linear tetrasaccharide(s), are the lowest molecular weight products of exhaustive hydrolysis of branched dextrans.

Culture Media↗
PubMed1979

Gas-liquid chromatographic test for honey adulteration by high fructose corn sirup.

A gas-liquid chromatographic (GLC) method has been developed to detect the addition to honey of high fructose corn sirup (HFCS). Samples are derivatized directly with trimethylsilane, cholestane is added as an internal standard, and the levels of maltose (includes other minor disaccharides) and isomaltose are determined after chromatography on OV-17. Domestic and imported honey samples (115) contained 2.00% maltose and 0.71% isomaltose. HFCS samples (21) contained 1.50% maltose, and 2.09% isomaltose. A discriminatory equation was developed (D = 2.73 - 5. 35 (Isomaltose/maltose)) and, when applied to the data for these samples and 37 adulterated samples, 81.4% of authentic honey samples and 78.4% of samples known to be adulterated with HFCS were correctly classified.

Chromatography, Gas↗
PubMed1991

A novel method for differentiating dextran sulfate from related sulfated polysaccharides.

A method is described for unequivocal identification of dextran sulfate, based on combined chemical desulfation and dextranase enzymolysis of dextran sulfate moieties to isomaltose, a specific indicator of dextran-type precursors. The method was developed using high-resolution (300 MHz) 1H NMR spectroscopy for assurance of the molecular transformations, identification, and estimation of the hydrolysis products. Overall conversion of approximately 80% of highly sulfated and moderately sulfated dextran sulfates was realized. Both 2-D 1H and 13C NMR spectra of a dextran sulfate (MW 500,000) clarified the extent of sulfation (75%) at C-4 and confirmed that sulfation at positions C-2 and C-3 was virtually complete. Estimation of the hydrolysis products (isomaltose, major; alpha-D-glucose, minor) is not restricted to 1H NMR now that the desulfation-enzymolysis methodology has been established; rather, it can be performed using HPLC or GLC (with derivatization).

Catalysis↗
PubMed1990

Catalytic mechanism of fungal glucoamylase as defined by mutagenesis of Asp176, Glu179 and Glu180 in the enzyme from Aspergillus awamori.

Asp176, Glu179 and Glu180 of Aspergillus awamori glucoamylase appeared by differential labeling to be in the active site. To test their functions, they were replaced by mutagenesis with Asn, Gln and Gln respectively, and kinetic parameters and pH dependencies of all enzyme forms were determined. Glu179----Gln glucoamylase was not active on maltose or isomaltose, while the kcat for maltoheptaose hydrolysis decreased almost 2000-fold and the KM was essentially unchanged from wild-type glucoamylase. The The Glu180----Gln mutation drastically increased the KM and moderately decreased the kcat with maltose and maltoheptaose, but affected isomaltose hydrolysis less. Difference in substrate activation energies between Glu180----Gln and wild-type glucoamylases indicate that Glu180 binds D-glucosyl residues in subsite 2. The Asp176----Asn substitution gave moderate increases and decreases in KM and kcat respectively, and therefore similar increases in activation energies for the three substrates. This and the differences in subsite binding energies between Asp176----Asn and wild-type glucoamylases suggest that Asp176 is near subsite 1, where it stabilizes the transition state and interacts with Trp120 at subsite 4. Glu179 and Asp176 are thus proposed as the general catalytic acid and base of pKa 5.9 and 2.7 respectively. The charged Glu180 contributes to the high pKa value of Glu179.

Amino Acid Sequence↗