Cytochrome P450 Monooxygenase Activity in the Dark Southern Subterranean Termite (Isoptera: Rhinotermitidae)

Abstract

Microsomal oxidases were characterized using surrogate substrates in the economically important dark southern subterranean termite, Reticulitermes virginicus (Banks). Aldrin epoxidase activity required NADPH and was inhibited by carbon monoxide and piperonyl butoxide (I50 = 4.72 ± 0.31 × 10-6M), indicating that the enzyme(s) involved was a cytochrome P450 monooxygenase. Aldrin epoxidase activity was highest at 22°C and pH 7.2. Also, the activity was linear up to 0.5 mg of protein per incubate and increased with reaction time up to 15 min. Although neither substrate nor cofactor was found to be a limiting factor, aldrin epoxidase activity failed to produce a linear response with respect to time at temperatures >22°C, indicating enzyme inhibition. Although increased incubation temperature >22°C resulted in decreased aldrin epoxidase activity, similar heat treatments did not result in a concomitant increase in cytochrome P420. Significant variation (2.7-fold) in aldrin epoxidase activity was observed among 4 R. viriginicus colonies collected from different locations in Florida. Additionally, cytochrome P450 and b5 content, cytochrome c reductase, and methoxyresorufin O-demethylase activities were measured in R. virginicus.