Degradation profile of [His7]-corazonin in the hemolymph of the desert locust Schistocerca gregaria

Degradation of the neuropeptide [His7]-corazonin, a key hormone in phase transition in locusts was studied using [3H][His7]-corazonin, RP-HPLC and mass spectrometry. After 4 h incubation, 50 and 75% of [His7]-corazonin could still be found in hemolymph of gregarious and solitarious Schistocerca gregaria, respectively. Under in vivo conditions the half-life was 30 min. These results are in contrast to many other neuropeptides that usually have half lives of a few minutes. The peptide is cleaved first by an endopeptidase, either just before or after the Tyr residue at position 5. Next, the C-terminal degradation fragments are further degraded by a dipeptidyl-peptidase, whereas the N-terminal fragments are further broken down one amino acid at a time. In addition, [Dopa5][His7]-corazonin was detected. Upon synthesis, this unexpected molecular modification turned out to be biologically active in bringing about cuticular melanization.