Introduction
Kassinin, a new peptide of amphibian origin, has been traced in the skin of the African frog Kassina senegalensis. Kassinin belongs to the tachykinin family which are peptides with the same consensus C-terminal sequence, viz. Phe-Xxx-Gly-Leu-Met-NH2. This common region, generally regard as the message domain, is considered to play an important role in activating the receptor. The divergent N-terminal region or the address domain, different in amino acid sequence and length, is thought to have an effect on the determination of the receptor subtype specificity. Kassinin, with the sequence that is Asp-Val-Pro-Lys-Ser-Asp-Gln-Phe-Val-Gly-Leu-Met-NH2, has been found to be capable of stimulating ion transport in skin.
Pharmacologic action
Stimulating ion transport in skin can be achieved by peptide in the part of which exceeding the C-terminal pentapeptide there must be either 2 Pro residues or 1 Pro and at least 1 basic amino acid present. From the C-terminus, kassinin possesses 1 Pro residue and 2 amino acids in position 9, 10, 11 respectively. As a result, kassinin has the ability to stimulate ion transport in skin. Kassinin works by fully activating NK1-like receptors in amphibians (NK2 preferring in mammals) with a peculiar molecular mechanism.
Function
Kassinin, a member of the tachykinin family of neuropeptides, is an active peptide which shows vast and complex pharmacological and physiological actions. For example, kassinin is able to stimulate ion transport in skin by interacting with corresponding receptors. In addition, kassinin can excite neurons and evoke a series of behavioral responses such as vasodilation, stimulation of extra-vascular smooth muscle and so on.
Pharmacokinetics and metabolism
Under the action of kassinin, the short-circuit current in skin arrives at its maximum value as soon as 10 minutes with the increase of 26.13±1.53 μA/cm2, and a decline to basal value occurs subsequently. Kassinin stimulating the increase of the short-circuit current is never significantly affected by any of three antagonists specific for mammalian NK1, NK2 and NK3 which are CP99994, SR48968, SB222200 respectively.
References:
Lippe, C., Bellantuono, V., Ardizzone, C., & Cassano, G. (2004). Eledoisin and Kassinin, but not Enterokassinin, stimulate ion transport in frog skin. Peptides, 25(11), 1971-1975.
Grace, R. C. R., Lynn, A. M., & Cowsik, S. M. (2001). Lipid induced conformation of the tachykinin peptide Kassinin. Journal of Biomolecular Structure and Dynamics, 18(4), 611-625.
Schwyzer, R. (1987). Membrane‐assisted molecular mechanism of neurokinin receptor subtype selection. The EMBO journal, 6(8), 2255-2259.
Anastasi, A., Montecucchi, P., Erspamer, V., & Visser, J. (1977). Amino acid composition and sequence of kassinin, a tachykinin dodecapeptide from the skin of the African frog Kassina senegalensis. Experientia, 33(7), 857-858.
