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Title: HYDROLYSIS OF INSECT NEUROPEPTIDES BY AN ANGIOTENSIN-CONVERTING ENZYME FROM THE HOUSEFLY, MUSCA DOMESTICA

Author
item LAMANGO, N - UNIVERSITY OF LEEDS
item Nachman, Ronald
item HAYES, T - TEXAS A&M UNIVERSITY
item STREY, A - TEXAS A&M UNIVERSITY
item ISAAC, R - UNIVERSITY OF LEEDS

Submitted to: Annals of the New York Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Insect neuropeptides are short chains of amino acids (the building blocks of proteins) that regulate a number of physiological processes critical for insect survival. For example, members of the insect kinin class of insect neuropeptides regulate water and mineral balance as well as digestive processes in a number of insects. Nevertheless, insect neuropeptides by themselves hold little promise as insect control agents because of their susceptibility to being degraded in the target insect. In this paper, we report on the degradation and inactivation of the insect kinins and several other classes of insect neuropeptides by an enzyme that is prevalent throughout the internal insect environment. These insect neuropeptides regulate such critical processes as reproduction and development, as well as water balance, in a variety of insect pests. Identification of the sites of attack by this degradative enzyme will allow for the design of mimics of the insect peptides that will resist such attack. This work leads us one step closer to the development of practical neuropeptide-like chemicals that will be effective in controlling certain pest insects but will be very environmentally friendly.

Technical Abstract: The presence in insect tissues of peptides with structural similarities to angiotensin I and to bradykinin, the two best known substrates of mammalian angiotensin-converting enzyme, has not been reported. As part of our study to identify potential substrates for insect angiotensin-converting enzyme, we have investigated the susceptibility of a number of known insect peptide hormones and neurotransmitters to hydrolysis by Musca domestica angiotensin-converting enzyme. Insect peptides belonging to the Red-Pigment Concentrating Hormone, leucokinin, locust tachykinin and depolarizing peptide families were hydrolysed by housefly angiotensin-converting enzyme, whereas proctolin and Crustacean Cardioactive Peptide were not substrates. Cus-DP II, LK 1, LK II and Lom-TK I were all cleaved at the penultimate C-terminal peptide bond to release a dipeptide amide as a major fragment with Km values of 94 +/- 11 uM, 634 +/- 81 uM and 296 +/- 35 uM for Cus-DP II, LK I and Lom-TK I, respectively. The ability of insect angiotensin-converting enzyme to hydrolyse C-terminally amidated peptides in vitro might be of functional significance since the enzyme has been localized to neuropile regions of the insect brain and is present in the haemolymph of houseflies.