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

[1][2] Like all tachykinins, physalaemin is a sialagogue (increases salivation) and a potent vasodilator with hypotensive effects.

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.

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.