Aldrin epoxidase

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)... 

Table V. Aldrin epoxidase requirements of C. riparius whole body homogenates under optimum conditionsa...

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). 

Table VI. Effect of FMN, FAD, and PBO upon in vitro C. riparius aldrin epoxidase in whole body homogenatesa...

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 VII. The effect of aldrin concentration and BSA upon aldrin epoxidase of . riparius whole body homogenates ...

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

Midges converted 58% of absorbed aldrin to dieldrin but midge epoxidase was completely inhibited in vitro and in vivo by PBO, demonstrating that PBO is a potent inhibitor of midge MFO... 

In vitro dieldrin production increased proportionally to larval concentration (enzyme concentration) up to 5 larvae/ml and each 10X increase in substrate (aldrin) concentration tripled and doubled, respectively, dieldrin formation. An approximation of 2 X 10-5 M aldrin as the Km value for midge epoxidase was obtained from a double reciprocal plot of data in Table VII, which closely corresponds to values for aldrin epoxidase in the house fly (28) and the southern armyworm (11). 

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...

Species Tissue Aldrin Epoxidase trans cis trans cis Esterase (X 10 J) Host Range... 

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...

Compound 1 Percentage in diet Aldrin epoxidase (nmol/min/mg protein) Cytochrome450 (nmol/mg protein)... 

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. 

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