Cytochrome P450 monooxygenase and glutathione S-transferase activity of two Australian termites: Mastotermes darwiniensis and Coptotermes acinaciformis

Abstract

The major detoxication enzymes have een characterized in preparations of two economically important termite species. Mastotermes darwiniensis microsomes contained a similar quantity of total cytochrome P450 as Coptotermes acinaciformis but the activities of aldrin epoxidase (AE), 7-ethoxyresorufin O-deethylase (EROD) and 7-ethoxycoumarin O-deethylase (ECOD) were 4.5, 5.8 and 17 times higher, respectively. Compared with other insects, AE activity in these two termite species is low, EROD activity moderate and ECOD activities are high, especially in M. darwiniensis. The cytosolic GST activity of C. acinaciformis toward chloro-3,5-dinitrobenzene (CDNB) was 3.13 μmol min −1mg −1, > 3 fold higher activity than M. darwiniensis cytosol. Apparent K m values of 1.87 mM for CDNB and 0.84 mM for glutathione were determined in C. acinaciformis cytosol. 7,8-Benzoflavone dramatically reduced EROD activity in microsomes of both termite species but had significantly lower inhibitory effect on ECOD activity. The addition of SKF 525A to termite microsomes inhibited both EROD and ECOD activities. Multiple isoenzymes of cytochrome P450 in termites are indicated by these findings. The distinctly different substrate specificities and λ max of the CO difference spectra from M. darwiniensis and C. acibnaciformis microsomes may arise from differences in the cytochrome P450 isoenzymes between the two species.