以亚油酸为底物，采用紫外分光光度法测定鲜枣脂氧合酶(lipoxygenase, LOX)的酶学特性及热失活动力学性质。考察了温度、pH、金属离子及络合物对LOX活性的影响，并建立了LOX酶促反应动力学及热失活动力学参数。结果表明：鲜枣LOX的最大吸收波长为265 nm；最适温度和pH分别为40 ℃、7.0；在pH值为5.0~6.0的环境中，LOX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0.14 mmol/L、0.26 U/min，鲜枣LOX与底物亚油酸的亲和力较好；且LOX的热失活遵循一级反应动力学规律，反应活化能为105.20 kJ/mol；2 mmol/L Cu2+和10 mmol/L Cu2+、Ca2+、Mn2+对LOX酶活力有激活作用(P<0.05)，而2 mmol/L Mn2+、Zn2+、Mg2+和10 mmol/L Mg2+，EDTA对LOX活性具有抑制作用(P<0.05)。该试验为鲜枣加工贮藏中LOX活性控制提供了有益的数据参考。

Using linoleic acid as a substrate, the enzymatic characteristics and thermal inactivation kinetics of lipoxygenase (LOX) from fresh jujube were studied by ultraviolet (UV) spectrophotometry. The effects of temperature, pH, metal ions, and complexing agents on LOX activity were investigated, and the kinetic parameters for the LOX enzymatic reaction and thermal inactivation were determined. The results showed that the maximum absorption wavelength of fresh jujube LOX was 265 nm, while the optimum temperature and pH were 40 ℃ and pH 7.0, respectively. LOX activity was relatively stable at pH 5.0~6.0. Kinetics of the enzymatic reaction followed the Michaelis-Menten equation for single-substrate enzyme-catalyzed reaction, and the values of Km and Vmax were 0.14 mmol/L and 0.26 U/min, respectively. Fresh jujube LOX showed good affinity to the substrate linoleic acid. In addition, the thermal inactivation of LOX could be described by a first-order kinetic model, and activation energy (Ea) was 105.20 KJ/mol. The enzyme activity was enhanced by 2 mmol/L Cu2+ and 10 mmol/L Cu2+, Mn2+, and Ca2+, but was inhibited by 2 mmol/L Mg2+, Zn2+, and Mn2+, as well as 10 mmol/L Mg2+ complexing agents (P < 0.05). The results provide useful reference data for the control of LOX activity during processing and storage of fresh jujube.

甘肃省教育厅科研项目(1109B-10)；甘肃省农业生物技术研究与应用开发项目(GNSW-2014-3)