【摘要】 研究了商品果胶酶的催化动力学特性.结果表明:果胶酶的最适pH为3.8,最适温度为50℃,酶在pH 3.4~4.2区域较稳定,在pH>4.5与pH<3.0下很快失活;酶在50℃以内具有较好的热稳定性,温度升高,酶的热稳定性下降,65℃下热变性2 h,酶活力降低80%.酶促反应动力学符合米氏双曲线方程,测得果胶酶水解果胶的米氏常数Km=(5.16±0.13)mg/mL,最大反应速度Vmax=(2.73±0.02)μg/(mL.min).Na+和K+对酶活力没有任何效应,0.1mmol/L Ca2+可使酶活力提高22.8%,5.0 mmol/L Zn2+对果胶酶活力的抑制达到17.4%,Mg2+、Mn2、Co2+、Hg2+和Ag+对果胶酶活力影响不大,Cu2+和Fe3+对果胶酶活力影响较大,浓度为5.0 mmol/L时,对果胶酶的抑制可分别达到88.9%和100%.更多还原

【Abstract】 The characteristics in catalytic kinetics of commercial pectinase from Aspergillus niger were determineded.The results showed that the optimum pH and optimum temperature of the enzyme for the hydrolysis of pectin（enzyme substrate）were pH 3.8 and 50 ℃,respectively.The behavior of the enzyme during hydrolysis of pectin followed Michaelis-Menten kinetics,with K_m=5.16±0.13 mg·mL^-1and V_max=2.73±0.02 μg·mL^-1·min^-1,at pH 3.8 and 50 ℃.The stability of the enzyme was investigated,and the results showed that the enzyme was stable in a pH range from 3.4 to 4.2 and at temperatures<50 ℃.The effects of metal ions on the enzyme were also studied.Na⁺ and K⁺had no influence on enzyme activity.Ca²⁺ in the concentration of 0.1 mmol/L increase activity of the enzyme,while Mg²⁺,Mn²⁺,Co²⁺,Ni²⁺,Hg²⁺,Ag⁺,Zn²⁺,Cu²⁺ and Fe³⁺ showed various degrees of inhibitory effects on the enzyme in the concentration of 5.0 mmol/L,among which Zn²⁺ in the concentration of 5.0 mmol/L inhibited activity of the enzyme by 17.4 %,and Cu²⁺ by 88.9 %,Fe³⁺ by 100 %.更多还原