The amino acid sequences of holokinins are homologous with those of bradykinins in vertebrates and wasps. Vertebrate bradykinins have a wide range of effects, mainly on the central nervous system and on smooth muscles. Holokinins had the most prominent effect among the peptides tested here and are the first fully characterized softening agent for sea cucumber dermis. As the only identified softening agents, the holokinins are unique. Their effect was easily suppressed by menthol, indicating that they can be classified as neuropeptides. Sequcen of Holokinin 1 is PLGYMFR(MW=883.06 g/mol)
Birenheide R, Tamori M, Motokawa T, Ohtani M, Iwakoshi E, Muneoka Y, Fujita T, Minakata H, Nomoto K. Peptides controlling stifness of connective tissue in sea cucumbers. Biol Bull. 1998 Jun;194(3):253-9. doi: 10.2307/1543095. PMID: 9664654.