EVIDENCE FOR A CONFORMATIONAL POLYMORPHISM OF INVERTEBRATE NEUROHORMONES - D-AMINO-ACID RESIDUE IN CRUSTACEAN HYPERGLYCEMIC PEPTIDES

Several large peptidic neurohormones have been isolated in crustaceans . In lobster and other related species, each of these neurohormones, a nd particularly the crustacean hyperglycemic hormone, occurs as two is oforms having the same peptidic sequence and molecular mass. We report here that these isoforms differ by the configuration of a single amin o acid residue. The third residue (Phe(3)) of the lobster hyperglycemi c hormones is in either the L- or D-configuration. In addition, we hav e shown that the biological activity of the two isoforms differs when considering the kinetics of their hyperglycemic effect.