| Summary: | 碩士 === 國立屏東科技大學 === 食品科學系所 === 97 === Onion（Allium cepa L., Hengchun） plant cells are rich in quercetin glycoside compounds. The quercetin is a kind of flavonoid compound that like other flavonoids have three similar ring chemical structures and their 3, 5, 7, 3’ and 4’ positions have hydroxyl group or glycoside group, respectively. These chemical structures were primary structure for their functional properties that were inhibited enzyme activity in onion. β-glucosidase (EC 3.2.1.21) is a kind of hydrolysis carbohydrate enzyme that exists in vegetable or fruit cells. When the plant structures were broken or extruded then their quercetin glycoside compounds were released and hydrolyzed by β-glucosidase. Therefore, the objective of this work is to study the biochemical characteristics of β-glucosidase in onion. Different sections were analyzed. Quercetin glycosides distribution in onion growth was investigated. The result showed that the quercetin glycosides content of germination was highest than others. The optimal temperature range for β-glucosidase was 30-50℃, and its optimal pH range was 5-8. The study also found that ethylenediaminetetraacetic acid (EDTA) have inhibition function for enzyme activity. After the adding EDTA, the residual enzyme activity was 32.5%. The anti-oxidation of α,α-diphenyl-β-pricrylhydrazyl (DPPH) test. Showed that germinate was the best on the clean free radical scavenging ability. Finally, the molecular weight of enzymes were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).It was found that the β-glucosidase of onion had two unit diploids structure and their molecular weights were 51 kDa and 67 kDa, respectively.
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