Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.21 (beta-glucosidase)
 3,280 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Aspergillus oryzae was found to secrete two distinct beta-glucosidases when it was grown in liquid culture on various substrates. The major form had a molecular mass of 130 kDa and was highly inhibited by glucose. The minor form, which was induced most effectively on quercetin (3,3',4',5,7-pentahydroxyflavone)-rich medium, represented no more than 18% of total beta-glucosidase activity but exhibited a high tolerance to glucose inhibition. This highly glucose-tolerant beta-glucosidase (designated HGT-BG) was purified to homogeneity by ammonium sulfate precipitation, gel filtration, and anion-exchange chromatography. HGT-BG is a monomeric protein with an apparent molecular mass of 43 kDa and a pI of 4.2 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing polyacrylamide gel electrophoresis, respectively. Using p-nitrophenyl-beta-D-glucoside as the substrate, we found that the enzyme was optimally active at 50 degreesC and pH 5.0 and had a specific activity of 1,066 micromol min-1 mg of protein-1 and a Km of 0.55 mM under these conditions. The enzyme is particularly resistant to inhibition by glucose (Ki, 1. 36 M) or glucono-delta-lactone (Ki, 12.5 mM), another powerful beta-glucosidase inhibitor present in wine. A comparison of the enzyme activities on various glycosidic substrates indicated that HGT-BG is a broad-specificity type of fungal beta-glucosidase. It exhibits exoglucanase activity and hydrolyzes (1-->3)- and (1-->6)-beta-glucosidic linkages most effectively. This enzyme was able to release flavor compounds, such as geraniol, nerol, and linalol, from the corresponding monoterpenyl-beta-D-glucosides in a grape must (pH 2.9, 90 g of glucose liter-1). Other flavor precursors (benzyl- and 2-phenylethyl-beta-D-glucosides) and prunin (4',5,7-trihydroxyflavanone-7-glucoside), which contribute to the bitterness of citrus juices, are also substrates of the enzyme. Thus, this novel beta-glucosidase is of great potential interest in wine and fruit juice processing because it releases aromatic compounds from flavorless glucosidic precursors.
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PMID:Purification, characterization, and substrate specificity of a novel highly glucose-tolerant beta-glucosidase from Aspergillus oryzae. 975 74

Quercetin, a polyphenol with potential health effects, is absorbed by humans and measurement in plasma can be used as a biomarker for intake. However, the chemical nature of the quercetin in blood is still not known, although one possibility is that glucosides are found in an unchanged form from the original food. We propose that the existence of quercetin glucosides in plasma is unlikely, since the metabolic beta-glucosidase capacity of the small intestine and of the liver is too great for quercetin glucosides to escape deglycosylation. We critically examine the limited number of studies which purport to detect quercetin glycosides in blood and the current evidence for the absorption of these compounds from the gastrointestinal tract. We emphasise the need for comprehensive identification of circulating compounds, since polyphenol glucuronides, the expected metabolites in plasma, have almost identical chromatographic properties to the glucosides at acid pH. Studies on the nature of quercetin metabolites in plasma are urgently needed so that the proposed biological activities of quercetin can be re-assessed and that a suitable biomarker of exposure can be established.
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PMID:Biomarkers for exposure to dietary flavonoids: a review of the current evidence for identification of quercetin glycosides in plasma. 1152 Apr 27

Flavonoids have been studied extensively because they offer great potential health benefits. In this study, enzymatic hydrolysis of glycosylated quercetin, kaempferol, and naringin was used to obtain their sugar-free aglycones. The investigation also employed a validated HPLC method to obtain the chiral disposition of the aglycone naringenin enantiomers. These analyses were conducted on exocarp, mesocarp, and seed cavity tissues of field-grown tomato (Lycopersicon esculentum Mill.) mutants (anthocyanin absent, atroviolacea, and high pigment-1) and their nearly isogenic parent (cv. Ailsa Craig) at immature green, "breaker", and red ripe maturity stages. Concentrations of all flavonoids using enzymatic hydrolysis were significantly higher than previously reported concentrations using acid hydrolysis. Presumably, this occurred due to a more specific and rapid hydrolysis of the glycoside moiety by the beta-glucosidase enzyme. The glycoside S-naringin was the predominant enantiomer in all fruit tissues, although the aglycones free R- and S-naringenin were detected in both exocarp and mesocarp. Whereas there was significantly more quercetin than kaempferol in exocarp tissue, they were present in about equal concentrations in the mesocarp. Quercetin concentrations were higher in the exocarp and mesocarp of immature green and breaker fruit of the high pigment-1 mutant than in the other genotypes, supporting the observed photoprotection and potential health benefits of the high pigment-1 tomato genotype.
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PMID:Disposition of selected flavonoids in fruit tissues of various tomato (lycopersicon esculentum mill.) Genotypes. 1630 74

Polygonum sachalinensis is a widespread invasive plant in Europe. Chemical profiles of its different organs were studied by HPLC-UV-ESI/MS. Seven major constituents quercetin-3-O-beta-D-galactopyranoside, quercetin-3-O-arabinopyranoside, lapathoside D, N-trans-feruloyltyramine, lapathoside C, hydropiperoside, and vanicoside B were isolated and identified. The free radical-scavenging, alpha/beta-glucosidase, and acetylcholinesterase inhibitory activities of crude MeOH extracts and isolated compounds were studied. The structure-activity relationships were discussed. The chemical profiles revealed flavonoids and phenylpropanoids are the major compounds of all the organs of this plant. Quercetin-3-O-arabinopyranoside, lapathoside D, N-trans-feruloyltyramine, lapathoside C and hydropiperoside were isolated from this species for the first time. In the alpha-glucosidase bioassay, quercetin-3-O-beta-D-galactopyranoside, lapathoside D and N-trans-feruloyltyramine demonstrated stronger activities than the positive reference acarbose. The trend in scavenging power showed no relation to enzyme inhibition in the test models.
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PMID:Antioxidant and enzyme inhibition activities and chemical profiles of Polygonum sachalinensis F.Schmidt ex Maxim (Polygonaceae). 1969 67