| Summary: | 碩士 === 實踐大學 === 食品營養與保健生技學系碩士班 === 103 === Soy isoflavones comprises of glycosidic isoflavones and isoflavone aglucones. The glycosidic isoflavones are formed by β-linkage of aglucone with any glycosides. Previous studies have shown that lactic acid bacteria with a cell surface enzyme β- glucosidase may be able to hydrolyze the β glycosidic bond, including isoflavone glycosides, and produces glucose and the aglucones. Daidzein has been proved as an α- glucosidase inhibitor, may reduce the absorption of glucose. However, the inhibition mechanism is not clear. Furthermore, no evidence has shown the effectiveness of the use of lactic acid and soy isoflavone composition on α- glucosidase inhibition. Therefore, this study is to study: (1) α- glucosidase enzyme kinetics by Michaelis-Menten equation, Lineweaver-Burk plot to obtaine α- glucosidase Vmax and Km, (2) the inhibiton mechanism ofα- glucosidase by glucosidic isoflavone, daidzin and genstin, and aglucone, daidzein, genstein, respectively, (3) the effect of the fermentation broth of a lactic acid bacteria and soy isoflavone composition on α- glucosidase enzyme inhibition. The results show that: (1) the mechanism of α- glucosidase enzyme inhibition by isoflavone is uncompetitive inhibition, (2) α- glucosidase inhibition rate of aglcone genistein, daidzein is significantly greater than that of glucosidic isoflavone genistin, daidzin, (3) the fermentation broth of Lactobacillus casei A39 and soy isoflavone composition, which containing a higher genistein, daidzein concentration, shows a significant inhibition of α- glucosidase activity than that of unfermented group. Taken together, this study demonstrated that β-glucosidase of lactic acid cell surface can hydrolyze isoflavone glycoside and produces aglucones, daidzein and genistein, which may be able to effectively inhibit α- glucosidase activity, and belongs to an uncompetitive inhibition mechanism; furthermore, lactic acid bacteria and soy isoflavones together, may be used as a hypoglycemic or obesity prevention food composition.
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