Inhibition of ATP Dephosphorylation by Acaricides with Emphasis on the Anti-ATPase Activity of the Carbodiimide Metabolite of Diafenthiuron

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Abstract
3-(2,6-Diisopropyl-4-phenoxyphenyl)-1-tert-butylcarbodiimide(DFCD), a toxic metabolite and photodegradation product of the propesticide diafenthiuron, and dicyclohexylcarbodiimide (DCCD), a commonly used biochemical inhibitory probe, inhibited Mg2+-, Na+K+-, and Ca2+Mg2+-ATPase activities in preparations from bulb mites (Rhizoglyphus echinopus (Fumouze and Robin)), twospotted spider mites (Tetranychus urticae Koch), and bluegill (Lepomis macrochirus Rafinesque) brain. DCCD was more active than DFCD, but neither carbodiimide was very potent. A possible exception occurred with DCCD, which caused 100% inhibition of bulb mite oligomycin-sensitive Mg2+-ATPase activity at a concentration of 0.1 m M. Using house fly, Musca domestica L., thorax mitochondrial Mg2+- ATPase, we showed that the binding domain for both carbodiimides was in the F0 portion of the enzyme, probably the transmembrane proton channel which is the known site of DCCD binding in proton-translocating ATPases. Certain other specific acaricides were inhibitors (>50% at 0.1mM) of ATPase preparations from bulb mites. These acaricides included chloropropylate, bromopropylate, oxythioquinox, cyhexatin, and flubenzimine (Mg2+ and Na+K+-ATPase), and ovex, chlorbenside, and propargite (Mg2+-ATPase). The role of ATPase inhibition in the modes of acaricidal and insecticidal actions of diafenthiuron, the two carbodiimides, and the other compounds is discussed.

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