乙烯对α-淀粉酶活力、动力学和微环境的影响

Effect of Ethylene on the Activity,Kinetics and Microenvironment of α-Amylase in Vitro

用乙烯利释放出乙烯,研究其对α-淀粉酶活力、动力学及微环境的影响。结果表明:与对照组比较,低浓度乙烯提高α-淀粉酶活力,而高浓度乙烯抑制α-淀粉酶活力;乙烯对α-淀粉酶的最适pH值(pH 6.0)几乎没有影响,但对其最适温度改变,向高温方向偏移5℃。用高浓度和低浓度的乙烯处理α-淀粉酶,探讨乙烯对α-淀粉酶的反应机理,其水解动力学符合一级动力学方程(Michaelis-Menten),其对应的双倒数曲线(Lineweaver-Burk)拟合度较好。紫外、荧光光谱分析表明:随着乙烯浓度增加,α-淀粉酶紫外吸光度和荧光发射强度明显增强。与对照组相比,紫外吸收光谱在波长229 nm红移1 nm。α-淀粉酶溶液的黏度随着乙烯浓度的增加而下降,导致酶的微环境改变。目前,乙烯利已广泛应用于各种蔬菜、水果,本研究对乙烯的食品安全有非常重要的意义。

The effects of ethylene on a-amylase activity, kinetics and microenvironment were investigated. Compared with the control group, a-amylase activity was enhanced by ethylene at low concentration but inhibited at high concentration. However, ethylene hardly affected the optimum pH （6.0） for a-amylase, whereas it resulted in an increase in the optimum temperature by 5 ℃ The hydrolysis kinetics of a-amylase in the presence of low and high concentrations of ethylene followed a first-order kinetic equation （Michaelis-Menten）, and the Lineweaver-Burk double-reciprocal curves were well fitted. The mechanism of action of ethylene in this respect was investigated. The ultraviolet （UV） absorption and fluorescence emission intensity of ？-amylase were obviously enhanced with increasing ethylene concentration, and the absorption peak of a-amylase at 229 nm showed a red shift by 1 nm. After ethylene was added, the viscosity of a-amylase solution declined obviously compared with the control group, leading to a change in the microenvironment of a-amylase. This research is of great significance for supporting the safe application of ethylene in fruits and vegetables.