אסיף מאגר המחקר החקלאי

Acetylcholinesterase of Aphis citricola: Properties and significance in determining toxicity of systemic organophosphorus and carbamate compounds

Year:

1981

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Volume :

15

Co-Authors:

Manulis, S., Division of Entomology, The Volcani Center, ARO, Bet Dagan, Israel
Ishaaya, I., Division of Entomology, The Volcani Center, ARO, Bet Dagan, Israel
Perry, A.S., Laboratory of Environmental Toxicology, Institute for Nature Conservation Research, Tel Aviv University, Ramat Aviv, Israel

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Abstract:

In apterous adults of the spirea aphid, Aphis citricola van der Goot, the optimum conditions for determining acetylcholinesterase (AChE) activity consist of reaction mixture of 0.1 M phosphate buffer (pH 7.5), 10-3 M acetylthiocholine (ASCh), and enzyme extract equivalent to 80 ± 3 μg protein incubated for 15 min at 30°C. The Km value for ASCh (6.7 × 10-5 M) was much lower than that of butyrylthiocholine (BuSCh) (1.25 × 10-2 M). The enzyme activity was almost completely inhibited by 10-6 M paraoxon or 10-5 M eserine and was 84% inhibited by 10-5 M BW284C51 (a specific AChE inhibitor). DTNB was found to inhibit the enzyme activity and was therefore added at the end of the reaction. AChE activity of A. citricola was inhibited in vitro and in vivo by dimethoxon > dimethoate, and aldicarb sulfoxide > aldicarb > aldicarb sulfone. The in vivo effect correlates well with the toxicity level of the various toxicants. A neurotoxicity index which combines both mortality and in vivo inhibition of the aphid AChE activity is suggested as a measure for determining the toxicity of organophosphorus and carbamate compounds toward aphids. © 1981.

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