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)

Studies of substrate and cosubstrate specificities of mould alpha-glucosidases suggest that the binding site of the active center of mould alpha-glucosidase consits of two subsites--glucone and aglucone ones. The glucone site is capable to bind glucose and mannose, whereas the aglucone one- some compounds whose affinity for the enzyme may be expressed as follows: glucose greater than galactose greater than paranitrophenol greater than or equal to glycerol greater than ethanol approximately equal to methanol. Upon interaction of enzyme with alpha-D-glucoside the formation of a productive enzyme-substrate complex occurs when the glucosyl residue located at the non-reducible end of the substrate molecule occupies the glucone subsite and aglucone of the substrate occupies the aglucone subsite of the enzyme. After removal of the first product from the aglucone subsite the substrate is bound at this subsite. It is assumed that under cosubstrate excess it is capable to bind at the aglucone subsite prior to the removal of the first product and the formation of the substituted form enzyme--glycosyl. Under these conditions the cosubstrate removes the substrate from the aglucone subsite resulting in a formation of a non-productive tertiary complex enzyme--substrate--cosubstrate. The anomeric configuration of glucose produced under the action of alpha-glucosidase on maltose and starch was determined using a kinetic method.
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PMID:[Specificity of fungal alpha-glucosidases]. 91 42

Intravenous infusions of maltose were performed using human volunteers. Four volunteers received maltose in a dose of 0.25 g/kg bodyweight and hour during eight hours. A follow-up period of three hours was added. Six volunteers received maltose in a dose of 0.125 g/kg bodyweight and hour during twelve hours. Only with the lower dose of maltose (0.125 g/kg b.w.) a steady state is reached after six hour continuous infusion. However even under these conditions maltose concentration in blood reaches the high concentration of 70 mg/100 ml. Using the double infusion rate, no steady state is attained when the infusions lasted for eight hours, despite maltose concentration in blood measured 150 mg/100 ml at this time. By measuring different metabolic parameters (fatty acid concentration, phosphate concentration) it is shown that parenterally applicated maltose is metabolized in the human. On the other hand, adverse reactions were not observed. The concentrations of uric acid and bilirubin remain constant and the activity of SGOT is not altered. Renal excretion of sugar measures 25-35% of the maltose administered parenterally. It is concluded that the glucose in urine stems from direct intra tubular hydrolysis of maltose achieved by the neutral maltase of the kidneys. The lack of attaining constant blood concentration for maltose during the infusions and the high renal loss of sugar shows that maltose is not suited as the single substrate for parenteral nutrition. However, there remains the possibility to use maltose in combination with glucose substitutes. The metabolic behaviour of maltose is similar to glucose, it differs from glucose substitutes.
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PMID:[Tests with human volunteers on parenteral utilization of maltose]. 96 14

Two methods are described which allow the quantitative assay of the lysosomal enzyme alpha-1,4-glucosidase in single fibroblasts. In the first procedure the substrate was maltose, and liberated glucose was measured with an enzymatic cycling procedure for reduced nicotinamide adenine dinucleotide phosphate. Single cultured fibroblasts were found to have enzyme activities in the range of 0.5-10 X 10(-13) moles glucose/hr. In the second procedure the artificial substrate 4-methylumbelliferyl-alpha-D-glucopyransodie was used. It is hydrolyzed in a single step reaction to the fluorescent product 4-methylumbelliferone (MU). By reducing the incubation volume and by measuring the fluorescence in microdroplets with a microscope fluorometer, a sensitivity of 10(-14) moles MU could be obtained. Activities were found ranging from 0.5-10 X 10(-14) moles MU/hr/cell. Both procedures for single cell analysis proved to be reliable when compared with conventional assays on cell homogenates. Cocultivation and cell fusion studies were performed to demonstrate that these methods can be used to study the metabolic and genetic interaction between normal and enzyme-deficient fibroblasts derived from patients with glycogenosis II.
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PMID:Methods for analysis of acid alpha-1,4-glucosidase activity in single hybrid cells. 106 91

Digestive enzymatic activities (disaccharidases, alkaline phosphatase, peptide hydrolases) have been determined in the mucosa of 14 patients with chronic pancreatitis. All had an abnormal secretin-pancreozymin test. Four patients had insulin-dependent diabetes mellitus, four a pathological glucose tolerance test. Nine patients had steatorrhoea. Maltase, sucrase, and alkaline phosphatase activity was significantly elevated in patients with exocrine pancreatic insufficiency, whereas those of lactase, trehalase, and peptide hydrolase were normal. Patients with steatorrhoea had higher maltase and sucrase activity than those without steatorrhoea, whereas decreased glucose tolerance had no effect on brush border enzymatic activity. It is suggested thatdecreased exocrine rather than decreased endocrine pancreatic function is responsible for the increase in intestinal disaccharidase and alkaline phosphatase activity, possible by the influence of pacreatic enzymes on the turnover of brush border enzymes from the luminal side of the mucosal membranes or by direct hormonal stimulation though cholecystokinin.
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PMID:Influence of exocrine and endocrine pancreatic function on intestinal brush border enaymatic activities. 109 2

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.
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PMID:The specificity of the synthetic reaction of two yeast alpha-glucosidases. 113 11

In this study we investigated the function of the obstructed small bowel of the rat, the behaviour of the mucosal enzymes, the metabolic changes of the small bowel wall and the morphology of the mucosa. We found a decrease of passive transport of 3H-Antipyrine which was equal after 24 and 48 hrs. The active transport of 14C-Glucose was found to be progressively inhibited after occlusion. The metabolic enzymes SDH, G-6-PDH, and GOT remained unchanged, LDH was increased after 48 hrs, which can be explained by enzyme induction. The lactate-pyruvate ratio in the tissue of the obstructed bowel was 3 times as high as in the controls. The brush-border enzymes maltase and especially the alkaline phosphatase are decreased with progressive obstruction, which probably is caused by diffusion into the lumen. By electron-microscopy there are no changes in the brush-border membrane but a swelling of mitochondria which is caused by hypoxia.
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PMID:[Functional and metabolic changes of the mucosa during the occlusion of the small bowel of the rat (author's transl)]. 121 48

In 63 infants and children with a histological normal mucosa of the duodenum, without an isolated defect of enzyme and with a normal increase of xylose and glucose in serum after a combined xylose-lactose loading test the activities of disaccharidases were log normal distributed. The asymmetric distributions were transformed into symmetric ones and the geometric mean (x) as well as the range (+/- 2 s) of maltase, saccharase, isomaltase, lactase and trehalase were calculated. Only the activity of lactase shows a significant dependency on age. In the first year of age the lower limit (x -- 2 s) of this enzyme is much higher than later.
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PMID:[Disaccharidases of the small intestine mucosa in infants and children. "Normal values", log normal distribution and age dependence]. 122 50

In three experimental groups of white rats receiving cacein in the morning, at noon and at night, over a period of one month, glucose resorption was studied in the hours of casein alimentation. The method of accumulating preparation from the mucosa "in vitro" was employed, and parallel to glucose resorption, maltase activity was also investigated. The results obtained are discussed in the light of modern concepts on membranous digestion and active transport, and more particularly, on interactions of the monomers at membrane level. Interpretation is made of the marked resorption of glucose, observed in the experimental group receiving casein at noon, and the possibility of practical application of the results recovered in rational dietetic nutrition is discussed.
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PMID:[Study of glucose resorption during rhythmic protein feeding in a chronic experiment on white rats]. 123 3

Studies have been carried out on activities of lysosomal beta-N-acetylhexosaminidase (hex), beta-galactosidase (beta-gal), alpha-glucosidase (alpha-glu), and acid phosphatase (AP) in serum and urine from patients with juvenile diabetes and matched controls. There is a large increase in blood and urinary hex activity (the former presenting three distinct patterns of abnormality), a moderate increase in urinary beta-gal, and a small increase in urinary alpha-glu activity, but no elevation of blood or urinary AP in the diabetics. Urinary alpha-glu activity in the diabetics shows striking inhibition by glucose, and this may reflect a similar phenomenon in vivo. Although glycohydrolase activities are elevated in patients with no detectable microangiopathy, more striking changes may be observed in patients with severe small-vessel disease. These alterations may be associated with increased glycoprotein catabolism in the diabetic, an area in need of further studies in the human and experimental diabetic animal.
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PMID:Altered lysosomal glycohydrolase activities in juvenile diabetes mellitus. 126 40

Adjunctive treatment with acarbose (possibLy together with sulphonylurea or insulin treatment) can be effectively utilised to achieve blood glucose control if postprandial hyperglycaemia is a problem and cannot be sufficiently controlled by dietary modifications. The alpha-glucosidase inhibitor, acarbose, should be taken with meals that are rich in complex carbohydrates and low in simple sugars, as recommended by diabetes associations, to achieve the greatest possible benefit from treatment.
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PMID:Nutritional recommendations for diabetic patients and treatment with alpha-glucosidase inhibitors. 128 May 73


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