Glutathione S-transferase in the Australian sheep blowfly,Lucilia cuprina (Wiedemann) |
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| Institution: | 1. Department of Pharmacognosy, Faculty of Pharmacy, Ege University, 35100, Bornova, Izmir, Turkey;2. Institute of Pharmaceutical Biology, Biocenter, Goethe University Frankfurt, Max-von-Laue-Str. 9, 60438 Frankfurt/Main, Germany |
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| Abstract: | Glutathione S-transferase in the Australian sheep blowfly, Lucilia cuprina, was studied using 3,4-dichloronitrobenzene (DCNB) and 1-chloro-2,4-dinitrobenzene (CDNB) as substrates. The optimum pHs for enzyme activity were 7.5–8.0 and 6.7–7.4 for DCNB and CDNB conjugations, respectively. Inclusion of glutathione and bovine serum albumin in the homogenizing buffer protected the glutathione S-transferase from inhibition by endogenous compounds present in extracts of final instar larvae and of adults less than 7–8 days old. Conjugation activities for DCNB and CDNB increased throughout larval development to reach a peak early in the pupal stage. Activity then decreased through the remainder of the pupal stage and for the first 6–7 days after emergence of the adult. Almost all of the decrease in activity during the first 6 days of the adult occurred in the abdomen, which accounted for 85% of total activity in the adult female at emergence but only 47% at 6 days. Larval DCNB conjugation activity was localized almost entirely in the fat body (94%), whereas only 50% of the CDNB conjugation activity was in the fat body with the remainder in the cuticle (25%), gut (15%), and blood (10%). Adult and larval enzyme was induced ca. three- to four-fold by sodium phenobarbital. The induction was associated with changes in apparent Vmax rather than apparent Km, suggesting that phenobarbital caused increased production of forms of enzymes already present rather than inducing synthesis of altered or new forms. |
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