右旋糖酐酶酶学特性及热失活动力学研究-《中国调味品》

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Title:: Enzymatic Characteristics and Thermal Inactivation Kinetics of Dextranase

摘要:: 以右旋糖酐为底物，采用DNS法测定右旋糖酐酶酶活，揭示其酶学特性及热失活动力学性质。考察了温度、pH、离子强度、常见食品添加剂对右旋糖酐酶活性的影响，并建立右旋糖酐酶酶促反应动力学及热失活动力学参数。结果表明：最适温度、pH和离子强度分别为60/65°C、5.5、0.015 mol/L；pH 5.5-9.5或乙醇添加量0-30%的环境常温保存30 min，酶活性保持相对稳定；酶促反应动力学符合米氏方程所描述的单底物酶促反应动力学，其Km和Vmax分别为0.01321 mol/L、0.5153 μmol·min-1·U-1；右旋糖酐酶的热失活遵循一级反应动力学规律，在60°C、含蔗糖0、200 g /L的环境下热失活速率常数分别为0.1268、 0.1105 min-1。2 mmol/L 亚硫酸钠对右旋糖酐酶活性具有抑制作用（P<0.05）。该试验为制糖行业和其他行业应用该酶提供较详细的数据支持。

Abstract:: Using dextran as substrate, the enzymatic characteristics and thermal inactivation kinetics of dextranase were studied by DNS method. The effects of temperature, pH, ionic strength and common food additives on the activity of dextran were investigated, and the kinetic parameters for the dextranase enzymatic reaction and thermal inactivation were determined. The results showed that the optimum temperature, pH and ionic strength were 60/65°C, 5.5 and 0.015 mol/L, respectively. pH 5.5-9.5 or ethanol dosage of 0-30% was stored at ambient temperature for 30 min, and the dextranase activity was relatively stable. Kinetics of the enzymatic reaction followed the Michaelis-Menten equation for single-substrate enzyme-catalyzed reaction, and the values of Km and Vmax were 0.01321 mol/L and 0.5153 μmol·min-1·U-1, respectively. The thermal inactivation of dextranase could be described by a first-order kinetic model, and the thermal inactivation rate constant was 0.1268 and 0.1105 min-1 at 60°C, 0 g/L sucrose and 200 g/L. The enzyme activity was inhibited by 2 mmol/L sodium sulfite (P<0.05). This experiment provides detailed data support for the application of dextranase in sugar industry and other industries.