Chiral amino acid analysis of hypertrehalosaemic neuropeptides of cicadas

Bayer M, König S, Marco H, Gäde G

Abstract

For more than two decades it has been known that the neurosecretory glands of the cicadas synthesize two Abstracts DGMS 2019 ROSTOCK 125isobaric peptides with hypertrehalosaemic activity. The amino acid sequence is identical (pGlu-Val-Asn-Phe-Ser-Pro-Ser-Trp-Gly-Asn-NH2), but some physical parameters like their retention time in RP-LC differ. Previously, it has been shown that the region Pro6-Ser7-Trp8 contained a variable structural feature. The synthetic peptide with d-Pro6 co-eluted with the more bioactive, more hydrophilic peptide. We have used acid hydrolysis and chiral derivatisation with a variant of Marfey`s reagent to verify racemization. However, the results unequivocally demonstrated the absence of d-Pro. This only leaves cis-trans isomerization at Pro6 as a possible explanation for the presence of these neuropeptide hormone twins.