Mode of Inhibition of Chitin Synthesis by Diflubenzuron
Diflubenzuron and related benzoylphenyl ureas have been found to inhibit chitin synthesis in insect integuments and midguts but the mode of action of the insecticides still remains unknown. Diflubenzuron was reported to inhibit chitin synthetase from brine shrimp (l), Lucilia cuprina and two other species of Dipteran insects (2). However, the insecticide was neither an in vitro inhibitor of the integumental chitin synthetase in Trichoplusiani and Hyalophora cecropia (3) nor the whole-body or midgut enzyme preparations in Tribolium castaneum (4), Stomoxys calcitrans (5, 6) and Mamestra brassicae (7, 8) Other hypotheses have been proposed including an inhibition of a proteolytic enzyme required for activation of the enzyme from a zymogen form (9) and an inhibition via active metabolites or as a blocking agent by direct binding to a non-chitin synthetase site important in chitin polymerization and fibrillogenesis (4). We proposed another mechanism (10, 11), that the insecticide may inhibit UDP-N-acetylglucosamine transport across the microvilli membranes in the midgut epithelial cells.
KeywordsOuter Face Tribolium Castaneum Peritrophic Membrane Chitin Synthesis Midgut Epithelial Cell
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