Eledoisin is an undecapeptide
Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...

 of mollusk origin, belonging to the tachykinin family of neuropeptides.

It was first isolated from the posterior salivary gland
Salivary gland
The salivary glands in mammals are exocrine glands, glands with ducts, that produce saliva. They also secrete amylase, an enzyme that breaks down starch into maltose...

s of two mollusk species Eledone
Eledone is a genus of octopuses in the family Octopodidae.-Species:* Eledone caparti Adam, 1950* Horned Octopus, Eledone cirrhosa * Eledone gaucha Haimovici, 1988* Combed Octopus, Eledone massyae Voss, 1964...

and Eledone aldovandi, which belong to the octopod order of Cephalopoda.

Other tachykinins from nonmammalian sources include kassinin
Kassinin is a peptide derived from the Kassina frog....

 and physalaemin
Physalaemin is a tachykinin peptide obtained from the Physalaemus frog, closely related to substance P. Its structure was first elucidated in 1964....

. The mammalian tachykinins substance P
Substance P
In the field of neuroscience, substance P is a neuropeptide: an undecapeptide that functions as a neurotransmitter and as a neuromodulator. It belongs to the tachykinin neuropeptide family. Substance P and its closely related neuropeptide neurokinin A are produced from a polyprotein precursor...

, NKA, and NKB have similar effects as tachykinins of nonmammals and have been more widely studied and characterized. These peptides exhibit a wide and complex spectrum of pharmacological and physiological activities such as vasodilation
Vasodilation refers to the widening of blood vessels resulting from relaxation of smooth muscle cells within the vessel walls, particularly in the large arteries, smaller arterioles and large veins. The process is essentially the opposite of vasoconstriction, or the narrowing of blood vessels. When...

, hypertension
Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...

, and stimulation of extravascular smooth muscle
Smooth muscle
Smooth muscle is an involuntary non-striated muscle. It is divided into two sub-groups; the single-unit and multiunit smooth muscle. Within single-unit smooth muscle tissues, the autonomic nervous system innervates a single cell within a sheet or bundle and the action potential is propagated by...


Eledoisin has the amino acid sequence pGlu-Pro-Ser-Lys-Asp-Ala-Phe-Ile-Gly-Leu-Met-NH. Like all tachykinin peptides, Eledoisin shares the same consensus C-terminal sequence, that is, Phe-Xxx-Gly-Leu-Met-NH. The invariant "Phe7" residue is probably required for receptor binding. "Xxx" is either an aromatic (phenylalanine, tyrosine) or a branched aliphatic (valine, isoleucine) side chain and is thought to be important in receptor selectivity. This common region, often referred to as the "message domain," is believed to be responsible for activating the receptor. The divergent N-terminal region or the "address domain" varies in amino-acid sequence and length and is believed to play a role in determining the receptor subtype specificity.
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