| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1990: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 1989: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1988: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
Investigations were made on an important detoxification enzyme, glutathione S-transferase and antioxidant enzymes, which remove toxic oxygen species from the cells, in the onion maggot, Delia (=Hylemya) antiqua and its related species, the seedcorn maggot, D. platura.
A glutathione S-transferase (GST) of the onion maggot was purified to apparent homogeneity by ammonium sulfate fractionation, anion exchange chromatography and glutathinoe-affinity chromatography. The enzyme was a homodimer of 50.0 kD with a subunit of 23.5 kD, and had and isoelectric point of 5.0. The bisubstrate reaction catalyzed by this enzyme followed a sequential mechanism rather than a ping-pong mechanism. The purified GST showed multiple functions in addition to glutathione conjugation : bilirubin and hematin binding, and glutathione peroxidase activity.
Effect of host plants and dietary quercetin on antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase. (GPOX), was studied in the onion and seedcorn maggots. SOD activity of the latter species was 1.7 times that of the former when the two species were grown on a synthetic diet devoid of plant secondary compounds. SOD activities of the two species feeding on respective host plants were 100-230% greater than those of larvae feeding on the synthetic diet. Synthetic diet containing 1.0% of quercetin, a prooxidant chemical in onion buds, elicited ca. 2.5 times increase in SOD activity in both species. CAT levels were very high, being unaffected by the diet or the addition of quercetin in both species. Strong inhibition of GPOX was observed in the onion maggot reared on onion and the synthetic diet containing 0.1% quercetin.
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