Physalaemin is a

tachykinin Tachykinin peptides are one of the largest families of neuropeptides, found from amphibians to mammals. They were so named due to their ability to rapidly induce contraction of gut tissue. The tachykinin family is characterized by a common C-termi ...

peptide obtained from the ''

Physalaemus ''Physalaemus'' is a large genus of leptodactylid frogs. These frogs, sometimes known as dwarf frogs or foam frogs, are found in South America. It is very similar to ''Leptodactylus'', a close relative, and indeed the recently rescribed ''Leptod ...

'' frog, closely related to substance P. Its structure was first elucidated in 1964. Like all tachykinins, physalaemin is a

sialagogue __NOTOC__ A sialogogue (also spelled sialagogue, ptysmagogue or ptyalagogue) is a drug or substance that increases the flow rate of saliva. Sialogogues can be used in the treatment of xerostomia (the subjective feeling of having a dry mouth), to st ...

(increases

salivation Saliva (commonly referred to as spit) is an extracellular fluid produced and secreted by salivary glands in the mouth. In humans, saliva is around 99% water, plus electrolytes, mucus, white blood cells, epithelial cells (from which DNA can be e ...

) and a potent

vasodilator Vasodilation is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. The process is the opposite of vasoconstriction, ...

with hypotensive effects.

Structure

Physalaemin (PHY) is known to take on both a linear and helical three dimensional structure. Grace et al. (2010) have shown that in aqueous environments, PHY preferentially takes on the linear conformation whereas in an environment that simulates a cellular membrane, PHY takes on a helical confirmation from the Pro⁴ residue to the C-Terminus. This helical conformation is essential to allow the binding of PHY to neurokinin-1 (NK1) receptors. Consensus sequences between Substance P (a mammalian tachykinin and agonist of NK1) and PHY have been used to confirm that the helical confirmation is necessary for PHY to bind to NK1.

Use In Research

Not only is PHY closely related to Substance P (SP), but it also has a higher affinity for the mammalian neurokinin receptors that Substance P can bind to. Researchers can make use of this behavior of PHY to study the behavior of smooth muscle - a tissue where NK1 can be found. Shiina et al. (2010) used PHY to show that tachykinins as a whole can cause the longitudinal contraction of smooth muscle tissue in esophageal tissue. Singh et Maji made use of PHY's similarity to SP along with its sequence similarity to Amyloid B-peptide 25-35 B(25-35) Despite its sequence similarity to SP, Singh et Maji showed that PHY had distinct amyloid forming capabilities . Under artificially elevated concentrations of tetrafluoroethylene (TFE) and a short incubation time, PHY was able to form amyloid fibrils. These fibrils originating from tackynins like PHY were also shown to reduce the neurotoxicity of other Amyloid fibers associated with amyloid induced diseases such as Alzheimer's disease.

References

Neuropeptides Pyrrolidones Phenols {{biochemistry-stub