Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Lactose 6'-O-sulphate, N-acetylneuraminyl-(alpha 2 leads to 3)-D-lactose 6'-O-sulphate, N-acetylneuraminyl ?-O-sulphate-(alpha 2 leads to 3)-D-lactose 6'0-O-sulphate, N-acetylneuraminyl ?-O-sulphate-(alpha 2 leads to 6)-D-lactose and N-acetylneuraminyl-(alpha 2 leads to 3)- and -(alpha 2 leads to 6))-lactose 6'-O-sulphate were prepared by chemical sulphation of lactose, N-acetylneuraminyl-lactose and tis isomers by using pyridine-SO3 reagent. 2. Significant kinetic differences were observed in the enzymic hydrolysis of the sulphated derivatives compared with unsubstituted substrates. 3. In the case of reactions catalysed by rat liver lysosomal and Clostridium perfringens neuraminidases (EC 3.2.1.18), the presence of an O-sulphate group in the N-acetylneuraminyl moiety affected the reaction by decreasing the Km and the Vmax, its presence in the galactosyl moiety affected the reaction by decreasing the Km and increasing the Vmax. and its presence in both N-acetylneuraminyl and galactosyl moieties decreased the Km and the Vmax. of the reaction. 4. Mixed-substrate reaction kinetic data indicated competition between the sulphated and unsubstituted substrates for the same active sites on the neuraminidase molecule. 5. Lactose 6'-O-sulphate neither behaved as a substrate nor acted as an inhibitor with respect to unsubstituted lactose and p-nitrophenyl beta-D-galactopyranoside when tested with lactase of suckling rat intestine and Escherichia coli beta-D-galactosidase (EC 3.2.1.23). 6. Preliminary investigation also indicated that, whereas glucose 6-O-sulphate and glucose 3-O-sulphate were were neither substrate nor inhibitor of glucose oxidase (EC 1.1.3.4), galactose 6-O-sulphate was oxidized half as fast as unsubstituted galactose by galactose dehydrogenase (EC 1.1.1.48).
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PMID:Effect of O-sulphate groups in lactose and N-acetylneuraminyl-lactose on their enzymic hydrolysis. 22 64

The general methodology used for the determination of lactose in milk is considered, namely, polarimetry, gravimetry, infrared, colorimetry, gas-liquid chromatography, and high pressure liquid chromatography. The criteria for selecting an ideal analytical method followed by the relevance of most of these criteria in enzymatic methodology are discussed. The principle of the Boehringer-Mannheim method is presented, i.e., lactose is hydrolyzed to glucose and beta-galactose in the presence of beta-galactosidase and water. beta-Galactose is then oxidized by nicotinamide-adenine dinucleotide to galactonic acid in the presence of beta-galactose dehydrogenase. The amount of reduced nicotinamide-adenine dinucleotide formed is stoichiometric with the amount of lactose and is measured at 340 nm in a spectrophotometer possessing a slit width of less than or equal to 10 nm. The results of a recent Association of Official Analytical Chemists collaborative study of the B-M method are presented. From the overall mean of results on all samples, determinations by the enzymatic method averaged .49% lower than by the Association of Official Analytical Chemists gravimetric method. Standard deviations were similar for three sets of blind duplicates, which ranged between 3.67 and 4.55% lactose. F-Values revealed that variations between means obtained by laboratories differed significantly as compared with variations within laboratory means. The method has received Official First Action recognition by Association of Official Analytical Chemists.
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PMID:Determination of lactose by an enzymatic method. 406 42

For the measurement of the enzymatic activity of GM1-ganglioside (II3 NeuAcGgOse4Cer, galactosyl-N-acetylgalactosaminyl-(N-acetylneuraminosyl) galactosyl-glucosylceramide) beta-galactosidase in crude enzyme samples, a microassay using nonradioisotopic GM1-ganglioside was devised. To reduce the volume of the reaction mixture and eliminate the interferences due to the fluorescent contaminants in the reaction mixture, NADH, a product after the oxidation of the released galactose with NAD and beta-galactose dehydrogenase, was fluorometrically estimated by use of high-performance liquid chromatography. By this method, as little as 10 pmol of galactose can be detected. Using rat brain homogenates as an enzyme sample, the several parameters were reexamined to define the optimal conditions for the assay. This assay method was also applied to human cultured skin fibroblast homogenates, and it was found that this method can be used for the diagnosis of GM1-gangliosidosis, instead of the usual method using the radioisotope-labeled natural substrate.
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PMID:A fluorometric microassay procedure for monitoring the enzymatic activity of GM1-ganglioside beta-galactosidase by use of high-performance liquid chromatography. 643 75

Neuraminidase (acylneuraminyl hydrolase, EC 3.2.1.18) from the influenza virus A/Hong Kong/68 (H3N2) was purified after treatment of the purified virus with sarcosyl (sodium laurylsarcosinate), centrifugation at 110 000 x g, and chromatography on DEAE-Sephadex and Sephadex G-200. It migrated as a single component during electrophoresis on polyacrylamide gel, and its molecular weight was estimated about 270 000. The enzyme was thermolabile, the activity being reduced to 60% in 10 min at 50 degrees C. The purified neuraminidase had an apparent Km value of 4.1 . 10(-3) M for 5-N-acetyl-2-O-(3-methoxyphenyl)-alpha-D-neuraminic acid and was able to release sialic acid with linkages alpha 2-3, alpha 2-6 and alpha 2-8 (with very different efficiency) from fetuin, gangliosides, colominic acid, and bovine and porcine submaxillary mucins. The enzymic activity was measured by several procedures: (A) spectrophotometric determination at 340 nm of the NADH produced in the reaction catalysed by beta-galactose dehydrogenase on beta-galactose + NAD+, this beta-galactose was the product released from lactose by beta-galactosidase and lactose was the product of the neuraminidase activity on N-acetylneuraminyl-lactose; (B) determination of the colored quinone yielded by the liberated methoxyphenol with 4-aminoantipyrine (Santer, U.V., Yee-Foon, J. and Glick, M.C. (1978) Biochim. Biophys. Acta 523, 435-442); (C) periodate-thiobarbiturate procedures (Warren, L. (1959) J. Biol. Chem 234, 1971-1975 or Aminoff, D. (1961) Biochem. J. 81, 384-391). Some peculiarities of these methods are discussed.
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PMID:Neuraminidase from influenza virus A (H3N2): specificity towards several substrates and procedure of activity determination. 721 37

The objective of this collaborative study was to determine the method performance characteristics of a spectrophotometric enzymatic assay for measuring the lactose content of fluid milk. The principle behind the method is similar to that of AOAC Method 984.15 but with significant modifications and added quality control. Additionally, lactose concentration is expressed on a weight/weight (wt/wt) rather than a weight/volume (wt/vol) basis. The principle of the method is the hydrolysis of lactose to D-glucose and D-galactose by beta-galactosidase, followed by the oxidation of beta-D-galactose by nicotinamide adenine dinucleotide (NAD+) in the presence of beta-galactose dehydrogenase. The reaction is catalyzed by the addition of aldose-l-epimerase, which accelerates the mutarotation of alphha-D-galactose to beta-D-galactose. The amount of reduced nicotinamide adenine dinucleotide (NADH) formed is measured at 340 nm and is proportional to the amount of lactose present. Important aspects of the assay include preparing the assay solution by weight (rather than volume), mixing the contents of the spectrophotometric cuvette without losing solution, inclusion of aldose-l-epimerase, specifying spectrophotometer characteristics, and accounting for the optical path length of the spectrophotometric cuvettes. In the collaborative study, 11 laboratories tested one lactose standard and 8 pairs of blind replicate raw, processed, and formulated milks with an anhydrous lactose content between 3.0-7.2%. Statistical performance, in units of g/100 g anhydrous lactose, for the milk materials within the applicability of the method was as follows: mean = 4.4040, Sr = 0.0130, SR = 0.0250, RSDr = 0.29%, RSDR = 0.57%, r = 0.0364, and R = 0.0700. Standard and marginal recoveries were 98.66 and 99.53%, respectively. Method performance represented a significant improvement over what would be achieved if path length was not accounted for or the assay was done volumetrically. The Study Directors recommend that the method for determination of the lactose content of fluid milk by the spectrophotometric enzymatic method using weight additions and path length adjustment be adopted Official First Action.
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PMID:Determination of the lactose content of fluid milk by spectrophotometric enzymatic analysis using weight additions and path length adjustment: collaborative study. 1737 52