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)

A new substrate, 3-ketobutylidene beta-2-chloro-4-nitrophenylmaltopentaoside (3KB-CNPG5), was used for the determination of alpha-amylase (EC 3.2.1.1) in serum and urine. Under this alpha-amylase assay condition, 3KB-CNPG5 is resistant to glucoamylase and alpha-glucosidase, which are auxiliary enzymes, because the 4- and 6-positions of the non-reducing-end glucose residue are modified by the 3-ketobutylidene group. The assay using 3KB-CNPG5 for alpha-amylase activity is a highly sensitive method that uses 2-chloro-4-nitrophenol (CNP) as an aglycone, and is a stable method for determination of alpha-amylase activity in biological fluids.
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PMID:Determination of alpha-amylase using a new blocked substrate (3-ketobutylidene beta-2-chloro-4-nitrophenyl-maltopentaoside). 193 99

Flavonoids (103 species) were tested for inhibitory activity against mouse liver sialidase using sodium p-nitrophenyl-N-acetyl-alpha-D-neuraminate (PNP-NeuAc) as substrate. Isoscutellarein-8-O-glucuronide from the leaf of Scutellaria baicalensis showed most potent activity (IC50, 40 microM), and this flavone appeared to be a non-competitive inhibitor of the enzyme. This flavone inhibited the lysosomal solubilized sialidase against PNP-NeuAc and sialyllactose effectively, but not microsomal enzyme against gangliosides and colominic acid, whereas, negligible or weak inhibitory activities were observed for influenza virus sialidase, beta-galactosidase, alpha-mannosidase, and alpha-glucosidase tested. These results indicate that this flavone may be useful to elucidate the function of the lysosomal solubilized sialidase.
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PMID:Inhibition of mouse liver sialidase by plant flavonoids. 277 64

The determination of alpha-amylase activity using an ethylidene-blocked 4-nitrophenyl-maltoheptaoside (EPS) has been evaluated in five laboratories on eight different analysers at 25 degrees C, 30 degrees C and 37 degrees C. The protecting ethylidene group inhibits hydrolysis at the non-reducing end of the substrate molecule by the auxiliary enzyme, alpha-glucosidase. The combined reagent is therefore stable for at least 10 days at 2-8 degrees C. HEPES is used, because the molar absorbance of 4-nitrophenol is independent of temperature in the presence of this buffer. Compared with the method using unprotected substrate 4-nitrophenyl-alpha-D-maltoheptaoside (4NP-G7), the present method is equal or better with respect to the imprecision, linearity and interlaboratory transferability of results in human and control sera. Since the protected and unprotected substrates differ in their turnover rate, the new assay yields activities which differ from those of the 4-nitrophenyl-alpha-D-maltoheptaoside method. Based on the homogeneous results obtained in method comparisons between EPS and 4-nitrophenyl-alpha-D-maltoheptaoside, and in order to maintain the 4-nitrophenyl-alpha-D-maltoheptaoside reference values, a conversion factor was derived to eliminate the above differences: activityEPS x 2.50 = activity4NP-G7. The temperature and instrument independence of this relationship was demonstrated in a total of 720 human sera and plasmas.
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PMID:Evaluation of a new alpha-amylase assay using 4.6-ethylidene-(G7)-1-4-nitrophenyl-(G1)-alpha-D-maltoheptaoside as substrate. 278 87

A new chromogenic substrate that is blocked at the nonreducing end, 4,6-benzylidene-alpha-D-4-nitrophenylmaltoheptaoside, is used to determine alpha-amylase (EC 3.2.1.1) activity in serum in a coupled assay with alpha-glucosidase (EC 3.2.1.20) and glucoamylase (EC 3.2.1.3) as auxiliary enzymes. The duration of the lag phase between 25 and 37 degrees C is less than 90 s, and the molar absorptivity of 4-nitrophenol is constant. The main cleavage product of the substrate by human pancreatic and salivary alpha-amylase is 4-nitrophenylmaltoside; in the presence of the auxiliary enzymes, greater than 95% of hydrolyzed substrate is accounted for as 4-nitrophenol. The combined reagent is stable for at least 20 days at 2-8 degrees C; precision is good, with CVs ranging from 1.7 to 3.3%; and the correlation of results with those by the 4-nitrophenylmaltoheptaoside method is excellent. Heparin (40 kilo-int. units/L), ascorbic acid (2.8 mmol/L), bilirubin (430 mumol/L), hemoglobin (170 mumol/L), glucose (55 mmol/L), and triglycerides (11 mmol/L) do not interfere in the assay.
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PMID:Rapid determination of alpha-amylase activity by use of a new chromogenic substrate. 310 53

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

A novel substrate, beta-2-chloro-4-nitrophenylmaltopentaoside (beta CNPG5), was used for the enzyme-coupled determination of alpha-amylase in biological fluids. It was hydrolyzed specifically by alpha-amylase to about 90% producing beta-2-chloro-4-nitrophenylmaltoside (beta CNPG2) and maltotriose. Under the assay conditions, the absorption of 2-chloro-4-nitrophenol (CNP) generated by the secondary reaction of alpha-glucosidase and beta-glucosidase as auxiliary enzymes is about twice the absorption of 4-nitrophenol (PNP), which is the end product currently measured in some alpha-amylase assay methods. The sensitivity of the assay using beta CNPG5 was thus much higher than that using 4-nitrophenyl-maltopentaoside (PNPG5) as substrate. The absorption of CNP did not fluctuate with temperature or with pH between 6.8 and 7.2, which are the conditions normally used for determination of amylase activity in biological fluids.
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PMID:Determination of alpha-amylase in biological fluids using a new substrate (beta-2-chloro-4-nitrophenyl-maltopentaoside). 387 77

We evaluated the enzymic mechanism by which alpha-4-nitrophenyl maltoheptaoside serves as a substrate for serum amylase (EC 3.2.1.1). Because polymeric substrates possess many potential sites of cleavage, the expression of enzymic activity as the number of micromoles of substrate transformed under defined conditions by an enzyme must be changed to "one microequivalent of group transformed." Therefore, we measured the activity of the isoenzymes of alpha-amylase with regard to suitable oligosaccharide substrates, which allowed us to express the catalytic activity in IUB units (U). By "high-performance" liquid chromatography we investigated the mechanism of human pancreatic and salivary alpha-amylase action, both alone and in combination with alpha-glucosidase (EC 3.2.1.20). On the basis of these results, we can describe exactly the entire reaction sequence and determine the stoichiometric coefficient of 4-nitrophenol within 0.02 mol/L (SD) produced under the assay conditions.
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PMID:Mechanism of action of human pancreatic and salivary alpha-amylase on alpha-4-nitrophenyl maltoheptaoside substrate. 618 12

Synthesis of beta-maltosides, p-nitrophenyl-beta-D-maltoside and 4-methylumbelliferyl-beta-D-maltoside, based on interaction of hepta-acetate-beta-D-maltosyl fluoride with the corresponding trimethylsilyl ethers of p-nitrophenol and 4-methylumbelliferone is described. 2-Chloro-4-nitrophenyl-beta-D-maltoside was synthesized by interaction of hepta-acetate-alpha-D-maltosyl bromide with 2-chloro-4-nitrophenol in two phase system using phase transfer catalyst. The method of assay of neutral alpha-glucosidase from human kidney and urine using synthesized beta-maltosides (p-nitrophenyl-beta-D-maltoside, 2-chloro-4-nitrophenyl-beta-D-maltoside and 4-methylumbelliferyl-beta-D-maltoside) as substrates and beta-glucosidase as an auxiliary enzyme is proposed. The method is simple, convenient and 10-fold more sensitive than the commonly used alpha-glucosidase assay procedure with the corresponding synthetic alpha-glucosides, p-nitrophenyl-alpha-D-glucoside and 4-methylumbelliferyl-alpha-D-glucoside. A modification of the method, with p-nitrophenyl-beta-D-maltoside as substrate, was applied to the semi-automatic assay of urinary alpha-glucosidase in 96-well microtitre plates.
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PMID:[Synthesis of beta-maltosides, derivatives of p-nitrophenol, 2-chloro-4-nitrophenol, and 4-methylumbelliferone, and their use as substrates for determining alpha-glucosidase activity]. 925 25

Intestinal transport and metabolism of p-nitrophenyl alpha-disaccharides were studied. In the absorption of p-nitrophenyl alpha-melibioside, no compounds other than p-nitrophenyl alpha-melibioside were detected on either the mucosal or the serosal side. In the absorption of p-nitrophenyl alpha-maltoside, on the other hand, p-nitrophenyl alpha-glucoside was formed on the mucosal side to appear on the serosal side. p-Nitrophenol and p-nitrophenyl beta-glucuronide also appeared on the serosal side in the absorption of p-nitrophenyl alpha-maltoside, and the total amount transported to the serosal side was significantly decreased in the absence of Na+ (a cosubstrate of Na+/glucose cotransporter (SGLT1)). Furthermore, the total transport clearance of p-nitrophenyl alpha-glucoside formed from p-nitrophenyl alpha-maltoside on the mucosal side in the p-nitrophenyl alpha-maltoside absorption, was similar to that of the absorption of p-nitrophenyl alpha-glucoside itself. These results led to the conclusion that the intestinal absorption of disaccharide conjugate depended on disaccharidase, and the absorption of the alpha-maltose conjugate occurred sequentially by the maltase-catalyzed hydrolysis of the disaccharide conjugate and SGLT1-mediated transport of the glucose conjugate.
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PMID:Intestinal metabolism and transport of alpha-disaccharide conjugates: the role of disaccharidase in the Na+/glucose cotransporter-mediated transport. 964 18

Replacement of the catalytic nucleophile Asp481 by glycine in Schizosaccharomyces pombe alpha-glucosidase eliminated the hydrolytic activity. The mutant enzyme (D481G) was found to catalyze the formation of an alpha-glucosidic linkage from beta-glucosyl fluoride and 4-nitrophenyl (PNP) alpha-glucoside to produce two kinds of PNP alpha-diglucosides, alpha-isomaltoside and alpha-maltoside. The two products were not hydrolyzed by D481G, giving 41 and 29% yields of PNP alpha-isomaltoside and alpha-maltoside, respectively. PNP monoglycosides, such as alpha-xyloside, alpha-mannoside, or beta-glucoside, acted as the substrate, but PNP alpha-galactoside and maltose could not. No detectable product was observed in the combination of alpha-glucosyl fluoride and PNP alpha-glucoside. This study is the first report on an "alpha-glycosynthase"-type reaction to form an alpha-glycosidic linkage.
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PMID:Alpha-glucosidase mutant catalyzes "alpha-glycosynthase"-type reaction. 1203 80


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