Structural elucidation and conformational properties of the toxin paralysin beta-Ala-Tyr.

Larval extracts of the homotetabolous insects (i.e., Neobelleria Bullata-Insecta Diptera), cause paralysis followed by death when injected into adult flesh flies. The reason for causing these lethal effects is because the extracts contain endogenous toxins widely spread over the class of insects. Since their major effect is the paralysis they are called paralysins and are present through all the development stages. Their concentration gradually increases from larvae stage over pupation to late pharate adults indicating that paralysins have an active role in the metamorphosis. The prototype pharmacologically important dipeptide beta-alanine-tyrosine was synthesized and submitted to conformational analysis studies in hydrophilic and amphoteric environments in order to reveal the stereoelectronic properties responsible for its activity.

The synthesis of an analogue of the locust CRF-like diuretic peptide, and the biological activities of this and some C-terminal fragments.

The synthesis is described of an analogue of the locust CRF-like diuretic peptide in which methionine in positions 1,3, and 13 is replaced by isosteric methyl-homoserine residues. This analogue has been tested for biological activity on Malpighian tubules in vitro, and feeding behavior in vivo. It is highly active in stimulating fluid secretion and accumulation of cAMP in tubules, and on increasing the latency to feed and reducing meal duration. A 15 residue fragment from the C-terminus of the CRF-like peptide, Locmi-DP(32-46), is fully active in the feeding assay, but has only weak ability to stimulate the accumulation of cAMP in tubules. Two smaller fragments, Locmi-DP(32-37) and Locmi-DP(41-46), were tested but neither had consistent biological activity in any of the assays used here. None of the peptides tested have any substantive activity in increasing cGMP in tubules.