Isolation of L-3-phenyllactyl-Phe-Lys-Ala-NH2 (Antho-KAamide), a novel neuropeptide from sea anemones.

We have isolated and sequenced the neuropeptide L-3-phenyllactyl-Phe-Lys-Ala-NH2 from the sea anemone Anthopleura elegantissima. This neuropeptide (named Antho-KAamide) has the unusual N-terminal L-3-phenyllactyl blocking group which has recently also been discovered in 2 other neuropeptides from sea anemones. We propose that the L-3-phenyllactyl residue renders Antho-KAamide resistant to nonspecific aminopeptidases, thereby increasing the stability of the neuropeptide after neuronal release. The existence of the L-3-phenyllactyl residue in 3 neuropeptides isolated so far suggests that this blocking group is more generally occurring.