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)

The kinetics of N-linked oligosaccharide processing and the structures of the processing intermediates have been examined in normal parental BW5147 mouse lymphoma cells and the alpha-glucosidase II-deficient PHAR2.7 mutant cells. The mutant cells accumulated glucosylated intermediates but were able to deglucosylate and process about 40% of their oligosaccharides to complex-type. This processing was not due to residual alpha-glucosidase II activity since the alpha-glucosidase inhibitors 1-deoxynojirimycin (DNJ) and N-butyl-DNJ did not prevent it. Parent cells also showed alpha-glucosidase II-independent processing in the presence of DNJ and N-butyl-DNJ. Membrane preparations from both parent and mutant cells had endo alpha-mannosidase activity, that is, split Glc1,2Man9GlcNAc to Glc1,2Man plus Man8GlcNAc, indicating that this was a candidate for an alternate route to complex oligosaccharide formation in the mutant cells. A balance study in which the cellular glycoproteins, intracellular water soluble saccharides, and saccharides secreted into the medium were isolated and analyzed from [2-3H]mannose-labeled mutant cells showed that the cells formed the di- and trisaccharides Glc1Man and Glc2Man in amounts equivalent to the deglucosylated oligosaccharides found in the cellular glycoproteins. This result shows unequivocally that the alpha-glucosidase II-deficient mutant cells use endo alpha-mannosidase as a bypass route for N-linked oligosaccharide processing.
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PMID:alpha-Glucosidase II-deficient cells use endo alpha-mannosidase as a bypass route for N-linked oligosaccharide processing. 182 11

High-pressure liquid chromatography and microcalorimetry have been used to study the thermodynamics of the hydrolysis reactions of a series of disaccharides. The enzymes used to bring about the hydrolyses were: beta-galactosidase for lactulose and 3-o-beta-D-galactopyranosyl-D-arabinose; beta-glucosidase for alpha-D-melibiose; beta-amylase for D-trehalose; isomaltase for palatinose; and alpha-glucosidase for D-turanose. The buffer used was sodium acetate (0.02-0.10 M and pH 4.44-5.65). For the following processes at 298.15 K: lactulose(aq) + H2O(liq) = D-galactose(aq) + D-fructose(aq), K0 = 128 +/- 10 and delta H0 = 2.21 +/- 0.10 kJ mol-1; alpha-D-melibiose(aq) + H2O(liq) = D-galactose(aq) + D-glucose(aq), K0 = 123 +/- 42 and delta H0 = -0.88 +/- 0.50 kJ mol-1; palatinose(aq) + H2O(liq) = D-glucose(aq) + D-fructose(aq), delta H0 = -4.44 +/- 1.1 kJ mol-1; D-trehalose(aq) + H2O(liq) = 2 D-glucose(aq), K0 = 119 +/- 10 and delta H0 = 4.73 +/- 0.41 kJ mol-1; D-turanose(aq) + H2O(liq) = D-glucose(aq) + D-fructose(aq), delta H0 = -2.68 +/- 0.75 kJ mol-1; and 3-o-beta-D-galactopyranosyl-D-arabinose(aq) + H2O(liq) = D-galactose(aq) + D- arabinose(aq),0H0 = 107 +/- 10 and delta H0 = 2.97 +/- 0.10 kJ mol-1.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Thermodynamics of hydrolysis of disaccharides. Lactulose, alpha-D-melibiose, palatinose, D-trehalose, D-turanose and 3-o-beta-D-galactopyranosyl-D-arabinose. 187 72

The high water permeability of kidney proximal tubules is of paramount importance for isotonic reabsorption of 70% of the glomerular filtrate, and water channels have been postulated to account for the high water permeability. Target analysis following radiation inactivation was used to probe the molecular size of the water channel. Samples of brush border membranes from rat renal cortex were subjected to 3-MeV electron pulses from the Van de Graaff accelerator at a temperature of -130 degrees C. The inactivation of the renal brush border enzymes, alkaline phosphatase, and maltase was used for internal standardization of accumulated dose measurements in target analysis of the water channel. Osmotic water permeability was measured by following the change in scattered light intensity upon rapid mixing of vesicles with a hypertonic solution using stopped-flow spectrophotometry. The vesicle shrinkage response was biphasic and the rate of the fast phase decreased dose dependently by irradiation corresponding to a target size of 30 +/- 3.5 kDa. The total change in scattered light intensity was unaltered, indicating that irradiation did not destroy the lipid barrier. Our results provide strong support for the hypothesis that the high osmotic water permeability of renal proximal tubules results from a water channel-specific protein with a functional unit of 30 kDa.
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PMID:Functional unit of 30 kDa for proximal tubule water channels as revealed by radiation inactivation. 188 92

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.
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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

The effect of supplementation of the diet with galactose on the age-related decline of intestinal lactase activity was investigated in 108 growing rats. Starting from 14 days of age, the rats were divided into two groups and fed with chow, and with fluid either as tap water or 5% galactose solution. At 14 days the specific lactase activity was 112.8 +/- 3.2 mumol min-1 (g protein)-1, which decreased to less than 10% of this value at maturity. Galactose supplementation did not prevent the decline. The increase of maltase, sucrase and trehalase was also unaffected. The result suggests that galactose plays no significant role in the regulation of disaccharidase activities in the rat.
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PMID:The effect on intestinal disaccharidase activity of feeding galactose to growing rats. 224 21

To determine whether zinc has a specific role on weight gain and intestinal disaccharidase activity, 42 male Sprague-Dawley rats were assigned to one of seven groups (n = 6 each). These were a baseline control group (0) that was killed to analyze initial intestinal disaccharidase (sucrase and maltase) activity, a second group (A) fed a zinc-deficient diet for 1 week, a third group (B) pair-fed control for A, a fourth group (C) fed a zinc-deficient diet for 2 weeks, a fifth group (D) pair-fed control for C, a sixth group (E) fed a zinc-deficient diet for 3 weeks, and a seventh group (F) pair-fed control for E. All experimental groups received distilled deionized drinking water, whereas control groups received zinc-enriched (25 micrograms of zinc/ml) distilled deionized water. Water was given ad libitum. After killing, the mucosa of the proximal half of the small intestine was analyzed for protein and disaccharidase activity, and liver, kidney, and heart were analyzed for zinc concentration. Protein content and disaccharidase activity of the jejunal mucosa in the experiment and control groups did not differ significantly. However, animals on the zinc-deficient diet demonstrated mildly depressed growth rates that were proportional to the duration of the experiment, and significantly lower zinc concentration in the kidney in the experimental groups. The data indicate that administration of a zinc-deficient diet for up to 3 weeks did not result in significant changes in intestinal mucosa protein content or in disaccharidase activity.
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PMID:Effect of zinc-deficient diet of varying duration on intestinal disaccharidase activity in the rat. 232 70

Physicians studied 16 moderately to severely malnourished infants 6 months old who had severe diarrhea for 2 weeks and did not gain weight. After admitting the infants, they administered total parenteral nutrition (TPN) to the infants through a central vein. As the infants began receiving TPN, they were randomly assigned to receive either banked human milk or sterile water by continuous nasogastric feeding for 2 weeks. In addition, before beginning nasogastric feedings and at the conclusion of the study, a physician performed a peroral biopsy of the small intestine. Small intestine perfusion studies were also done in the beginning and at the end of the 2 week period. More infants in the human milk group than in the sterile water group had 25% decrease in sucrase activity (p.02). Researchers noted that the villus/crypt ratio was similar in both groups at the beginning of the study and improved only in the sterile water group (p.002), but this was not a function of treatment. Additionally, more infants in the human milk group had an increase in the intraepithelial lymphocyte count than those in the sterile water group (milk, 5/7; water, 1/8; p.03). On the other hand, the data demonstrate that no differences existed in glucose and water absorption or in lactase and maltase activities as a function of the milk versus water treatment. Therefore, the results of this study suggest that human milk does not benefit small intestine mucosa recovery. Research to determine the effect of predigested formulas or specific factors in fresh human milk on the rate of mucosal recovery is needed.
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PMID:Human milk and the rate of small intestinal mucosal recovery in protracted diarrhea. 249 97

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.
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PMID:Thermodynamics of hydrolysis of disaccharides. Cellobiose, gentiobiose, isomaltose, and maltose. 249 94

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

Few data are yet available comparing the histological patterns of cadmium nephropathy with the values of urinary enzyme excretions, useful indexes of renal tubular damage. 40 Wistar rats, divided into four groups (A-D), were intoxicated with cadmium chloride (CdCl2) at 16 ppm in drinking water for 4, 16, 40 and 60 weeks, respectively. At the end of each period all the intoxicated rats and 5 controls were assessed for creatinine clearance, fractional excretion of gamma-glutamyltransferase (UfrGGT) and alpha-glucosidase (UfrAGL), indexes of anatomical tubular damage, and for fractional clearance of lysozyme (CfrLys), index of functional tubular damage. Thereafter, the rats were sacrificed and their kidneys examined with light and electron microscopy. Control rats and group A and B rats did not show any histological impairment. A widespread vesiculation of proximal tubular cells with mitochondrial and lysosomal alterations was found in the group C rats and was more evident in group D. The brush border never showed any damage in all groups in accordance with the finding of a normal excretion pattern of UfrGGT, an enzyme situated in this structure. The UfrAGL was increased only in group D rats (p less than 0.025), who showed the most severe anatomical damages. The CfrLys, an index of tubular function, was elevated in group C and D rats (p less than 0.02 and p less than 0.002, respectively). It was possible to detect the initial renal tubular damage.
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PMID:Detection of the early steps of cadmium nephropathy--comparison of light- and electron-microscopical patterns with the urinary enzymes excretion. An experimental study. 256 73


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