棉蚜不同品系羧酸酯酶的酶标仪动力学测定研究

Comparison of Carboxylesterase Activity Between Static Measuring Method and Kinetic Measuring Method in Various Strains of Cotton Aphid

用分光光度计终点测定法和酶标仪动力学测定法对3个抗性水平不同的棉蚜品系和1个敏感品系的羧酸酯酶进行了研究。以α-乙酸萘酯（α-NA）为底物时，敏感品系（S）和抗性品系R1，R2，R3终点测定法所需的最适酶量分别为1／2，1／20，1／33和1／100头蚜虫，β-乙酸萘酯（β-NA）为底物时分别为1／3，1／20，1／33和1／100头蚜虫。S品系对β-NA的水解活性明显高于α-NA，而抗性品系相反，对α-NA的活性明显高于β-NA。对α-NA水解的活性在不同品系间差异较大（近60倍），而对β-NA水解的活性差异小于对α-NA，最大约为14倍。用酶标仪动力学测定法研究表明，4个棉蚜品系间羧酸酯酶活性具有明显的差异，S，R1，R2和R3分别为38，85，198和762mOD·min-1·虫-1；与4个品系的抗性程度比较，酶动力学方法的测定结果更可靠。

Carboxylesterases of three resistant strains and one susceptible strain of cotton aphids, Aphis gossypii Glover, were studied using the method of end measurement and the kinetic method. The amount of enzymes used in the method of end measurement was equal to 1/2 or 1/3 for S strain, 1/20 for R1 strain (low resistance), 1/31 for R2 strain (moderate resistance) and 1/100 aphid for R3 strain (high resistance) respectively using α-naphthylacetate (α-NA) or β－naphthylacetate (β-NA) as substrate. Specific activity of carboxylesterase was lower using α-NA as substrate than using β-NA as substrate in S strain whereas specific activity was higher using β-NA as substrate than using β-NA as substrate in resistant strains. R3 strain was 60 or 14 times as high as S strain in specific activity of carboxylesterase when α-NA or β-NA was used as substrate. The results obtained by kinetic method showed that the various strains of cotton aphids differed significantly in specific activities of carboxylesterase and the values of carboxylesterase activities of S, R1,R2 and R3 strains were 38, 85, 198 and 762 mOD·min-1 aphid-1 reapectively. The specific activities of carboxylesterase were directly proportional to the levels of pyrethroid resistance in cotton aphids. The kinetic method of carboxylesterase measurement for monitoring pyrethroid resistance was more accurate than the method of end measurement.