Biochemical characteristics and in vitro inhibition of chitinase and acetylcholinesterase in Bemisia tabaci Gennadius (Hom: Aleyrodidae) | ||
| Journal of Pest Control and Environmental Sciences | ||
| Volume 14, Issue 1, June 2006, Pages 59-80 PDF (669.73 K) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/jpces.2006.460118 | ||
| Authors | ||
| F. A. El-Meniawi* 1; Seham M. Ismail2 | ||
| 1Department of Economic Entomology, Faculty of Agriculture, University of Alexandria | ||
| 2Central Laboratory of Pesticides, Sabahia, Alexandria, A.R.C. | ||
| Abstract | ||
| The biochemical interactions of five pesticides (malathion, phenothrin, cyhalothrin, diuron and chlorpropham) on the two important biological targets, chitinase and acetylcholinesterase (AChE), were investigated in Bemisia tabaci adults. Enzymes were isolated from B. tabaci adults and the optimal conditions for the enzymatic activity were identified. The optimal conditions for chitinase activity were at 37°C, 120 min incubation time, 1 µg protein concentration and pH 4.5, while they were at 35°C, 20 min incubation time, 2.2 µg protein concentration and pH 8.0 for AChE. In addition, the data proved that the activity of either chitinase or AChE was not dependent on the presence of CaCl2, MgCl2 and MnCl2 cations or EDTA and EGTA exogenous chemicals. Effects of tested pesticides on the in vitro enzymatic activity of chitinase and AChE isolated from female and male adults of the subject insect were evaluated. The results revealed that in case of chitinase, the significant reduction in the enzymatic activity was recorded for diuron and chlorpropham as the percentages of enzymatic inhibition were 80.4, 76.9% for females and 82.2, 78.6% for males, respectively. On the other hand, in case of AChE, the significant reduction in its activity was recorded for malathion only where the percentages of inhibition were 81.0, 86.0% for females and males, respectively. Besides, the I50 values for diuron and chlorpropham as the strongest inhibitors of chitinase activity were determined. I50 values for diuron were 0.27, 0.12 µM, while for chlorpropham they were 0.45, 0.15 µM for females and males, respectively. Moreover, the I50 values for malathion as the strongest inhibitor of AChE activity were 0.52, 0.25 µM for females and males of B. tabaci adults, respectively. Furthermore, the inhibition constant (Ki) values were determined for chitinase and AChE inhibitors. Values of Ki in the case of diuron were 40.0 and 15.0 µM whereas in case of chlorpropham, they were 52.0 and 18.0 µM for females and males, respectively. On the other hand, Ki values were 61.0 and 56.0 µM for B. tabaci females and males, respectively, in case of malathion. The results of the present study may add some forward steps to chitinase as a target for non conventional pesticides, especially those of phenylurea derivatives, in the IPM programs of the subject insect. | ||
| Keywords | ||
| Whitefly; Chitinase; AChE; Enzyme activity; Diuron; Chlorpropham; Phenylurea derivatives; Biochemical characteristics | ||
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