MODE OF ACTION OF 2 BENZOYLPHENYL UREAS AS INHIBITORS OF CHITIN SYNTHESIS IN INSECTS

An in vitro system for measuring the biosynthesis of chitin in housefly larvae is described. Isolated larval body walls convert [3H] -labelled glucosamine readily to [3H]-labelled chitin. Diflubenzuron, DU 19111 and polyoxin D inhibit the synthesis of chitin which results in an accumulation of [3H]-labelled uridinediphospho-N-acetylglucosamine in the treated body walls. The increase in UDP-[3H]-GlcNAc corresponds to the decrease in incorporation in chitin. This indicates that the polymerization enzyme, chitin synthetase, is the target for both benzoylphenyl urea insecticides and polyoxin D. Final proof that chitin synthetase in insects is the target for benzoylphenyl ureas can only be given when chitin synthetase can be isolated from insect tissue and studied in vitro. © 1979.