Aldrin epoxidase activity

The effect of pH on in vitro aldrin epoxidase activity was established over a pH range 6.5-8.5 (Figure 1). A pH of 7.5 was used as optimum. The effect of temperature on in vitro aldrin epoxidase activity was determined over a range of 20°-40°C (Figure 2). An optimum incubation temperature of 30°C was used. The maximum epoxidase activity was attained at a Tris-HCl buffer concentration of 5.0 X 10"1 M (Figure 3). 

The in vitro aldrin epoxidase activity was linearly correlateH-with homogenate concentration (enzyme concentration) over a range of 1 to 5 larvae/ml (Figure 5). 

Table VIII. Subcellular localization of aldrin epoxidase activity in C. riparjus larvae"...

Aldrin epoxidase activity (nmol/min/mg protein x 103) in larvae feeding on... 

Figure 9.5 Microsomal aldrin epoxidase activity in the developmental stages of the housefly. Iso-lan-B, carbamate-resistant strain SR, WHO standard reference strain. (From Yu, S.J. and Terriere, L.C., /. Insect Physiol., 20,1901,1974. With permission.)...

Figure 9.16 Aldrin epoxidase activity of midgut microsomes of sixth instar variegated cutworm larvae after feeding on fresh leaves of peppermint or bean and on an artificial diet. Mean SE of two experiments. (From Yu, S.J., et al., Pcstic. Biochem. Physiol., 12, 280,1979. With permission.)...

Table 9.15 Induction of microsomal aldrin epoxidase activity of variegated cutworm larvae fed secondary plant chemicals from peppermint...

Rose, H.A., The relationship between feeding specialization and host plants to aldrin epoxidase activities of midgut homogenates in larval Lepidoptera, Ecol. Entomol., 10,455,1985. 

Fed diets for 4 weeks containing daily doses equivalent to 3 mg PCB 105/kg BW, 0.05 mg PCB 126/kg BW, or 4.0 mg PCB 153/kg BW. Birds were killed 3 days after final treatment and livers analyzed for porphyrins, PCB residues, and activities of ethoxyresorufin O-deethylase-(EROD), aminopyrine-/V-demethylase (APND), and aldrin epoxidase (AE)... 

Dieldrin accumulated in proportion to incubation time during the first 30 min and declined thereafter, like the biphasic curves for aldrin epoxidation in other insects (11, 26). The rate curve declined continuously to 50% of maximum after 60 min of incubation at 30°C. BSA did not increase epoxidase activity in 15 min incubations (Table V) or 60 min incubations (Table IV). Consequently, reduced epoxidase activity is probably not due to endogenous proteases in the homogenate (1). 

The specific activity (protein basis) of aldrin epoxidase... 

Within expected variation, the optimum conditions for in vitro epoxidase activity of midges are typical of other insects. Maximum activity was obtained with 1 mg aldrin in 5 ml homogenate, an electron generator system with NADP, pH 7.5 buffer of 5 X 10-1 M and incubation for 15 min at 30°C. 

Midge aldrin epoxidase is highly active and may be completely inhibited ill vivo or iji vitro by PBO. 

This epoxidation of AFB has been associated with aldrin epoxidase (AE) activity in trout (30). As with other epoxide carcinogens, OAFB may be a substrate 7or epoxide metabolizing enzyme systems such as epoxide hydrase (EH) (EC4.2.1.63) and glutathione-S-epoxide transferase (GTr) (EC4.4.1.7) found in mammals and fish (31, 32, 33, 34). AFB also undergoes a variety of other reactions, generally to less toxic metabolites depending on the species of animal involved (35, 36). The primary AFB metabolite in rainbow trout has been shown to be a reduced form of AFB, aflatoxicol (AFL) (24). 

Table III. Effect Dietary Casein Levels on the in vitro Activities of Trout Hepatic Cytochrome c Reductase, Aldrin Epoxidase, and the Conversion of Aflatoxin B- to Aflatoxicol3...

In addition, important detoxification enzymes such as cytochrome P450 monooxygenases and glutathione S-transferases can be used as biomarkers for monitoring pesticide pollution. For example, Jensen et al. (1991) showed that treatment of rainbow trout (Onco-rhynchus mykiss) with endosulfan (as low as 8.3 ppb) induced two microsomal monooxygenase activities (7-ethoxyresorifin O-demethylase and aldrin epoxidase). Martinez-Lara et al. (1996) found that dieldrin and malathion induced individual isozymes of GST in the gilthread seabream, Sparus aurata. 

Table 9.2 The Difference in Specific Activity of Aldrin Epoxidase (Now Classified as One or More CYP Enzymes) between Two Strains of Housefly Rutgers and NAIDM...

NADH-dependent rates were generally 0 to 25% of NADPH-dependent ones, e.g. BPH of C. sapidus, C. maenas, B. eburneus and C. finmarchicus aldrin epoxidase and other MFO activities of Cambarus sp. ecdysone 20-monooxygenase of G. lateralis. Some MFO activities, however, had NADH-dependent rates similar to, or greater than, NADPH-dependent rates, viz. ECOD and ethylmorphine demethylase of A. astacus, and BPH of P. clarkii. 

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