|Harshini, S. - TRIVANDRUM UNIV, INDIA|
|Sreekumar, S. - TRIVANDRUM UNIV, INDIA|
Submitted to: Peptides
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 20, 2002
Publication Date: October 1, 2002
Citation: Harshini, S., Nachman, R.J., Sreekumar, S. 2002. In vitro release of digestive enzymes by FMRF amide related neuropeptides and analogues in the lepidopteran insect Opisina arenosella (Walk.). Peptides. 23(10):1759-1763. Interpretive Summary: Because of problems with the development of resistance to conventional pesticides, there is a critical need for new concepts and alternative approaches in controlling insect pests. The basic premise of this research is that neuropeptides (short chains of amino acids) serve as potent messengers in insects to regulate vital functions. New, selective control measures may be developed by designing metabolically stable mimics of these neuropeptides that actively inhibit or over-stimulate functions regulated by them. We report on work that demonstrates that some neuropeptides of the FMRFamide class stimulate release of digestive enzymes that metabolize proteins and carbohydrates, and others inhibit enzyme release. The study further delineates structural features important for either stimulation or inhibition of digestive enzyme release. A deeper understanding of how these neuropeptides regulate aspects of digestion will aid in the design of strategies to disrupt feeding and survival. The work brings us one step closer to the development of practical neuropeptide-like substances that will be effective in controlling pest insects in an environmentally friendly fashion.
Technical Abstract: The insect neuropeptides FMRFamide, leucomyosuppressin (LMS), and neuropeptide analogues leucosulfakinins (FLSK and LSK II Ser(SO3H)), perisulfakinin (PSK), proleucosulfakinin (PLSK), 14A[phi 1]WP-I, 542 phi 1, and 378A[5b]WP-I were assayed for their effects on the release of amylase and protease from the midgut tissue of larvae of Opisina arenosella. In the bioassay, empty midgut tubes ligated at both ends using hair were incubated with insect saline containing neuropeptides/analogues in a bioassay apparatus at 37 C for 30 minutes. After incubation the contents of the midgut preparations were analyzed for amylase and protease activity. In control experiments, the midgut preparations were incubated in insect saline without neuropeptides. The results of the study reveal that for stimulating amylase release from midgut tissue, the peptides require an FXRFamide (X may be methionine or leucine) sequence at the C-terminal. The presence of HMRFamide at the C-terminal of peptides may inhibit the release of amylase. Meanwhile, peptides with both FMRF and HMRFamide sequence at the C-terminal are found to be effective in stimulating protease release. The tetrapeptide segment at the C-terminus probably represents the active core of the neuropeptide.