Inhibitory Kinetics by Lactic Acid on beta-glucosidase from Hypocrea orientalis

Abstract

为探讨糖化共发酵同步进行的过程中发酵产物对纤维素酶活力的影响,研究了乳酸对纤维素酶组分中beta-葡萄糖苷酶(BG)活力的影响.结果显示:乳酸对; BG活力有不同程度的抑制,该作用具有显著的浓度效应,其半抑制浓度$I{C_{50}} = 019$; mol/L;乳酸对BG的抑制类型是可逆的竞争性抑制,抑制常数${K_1} = 0.149$; mol/L.应用底物反应动力学方法研究酶抑制动力学,建立了抑制动力学模型,发现乳酸对BG的影响是缓慢可逆失活的过程,底物对其有明显的保护作用,测; 得其正向速率常数${k_{ + 0}}$为0.4 L/(mol·min),逆向速率常数${k_{ - 0}}$为${\min ^{ -; 1}}$.该结果为纤维素糖化共发酵进程调控提供了理论依据.The kinetics of inhibition of beta-glucosidase purified from Hypocrea; orientalis by lactic acid has been studied.The results show that the; enzyme can be reversiblely inhibited by lactic acid with $I{C_{50}}$ of; 0.19 mol/L, while at low concentration the inhibition of the enzyme is a; slow,competitive type reaction and the inhibition constant (${K_1}$) is; 0.149 mol/L.The microscopic rate constants for the reactions of lactic; acid with the enzyme have been determined and the values of forward; (${k_{ + 0}}$) and reverse (${k_{ - 0}}$) inhibition constants are 0.4; L/(mol · min) and 0.056 ${\min ^{ - 1}}$,respectively.The presence of; the substrate has showed an obvious protective effect on the enzyme; against the inhibition by lactic acid. Our study provides the; theoretical support for lactic acid production industry by simultaneous; saccharification-fermentation of cellulose.国家海洋局海洋公益性项目; 福州大学校人才基