The tachykinin familyconsists of amidated neuropeptidesthatshare a carboxyterminalsequence (Phe-X-Gly-Leu-Met-NH2).
Preprotachykinin I, also designated protachykinin 1 precursor (PPT), is a common precursor of tachykinins.
Preprotachykinin I alternatelysplicesto formvariousisoforms.
These isoforms include: Substance P; Neurokinin A (NKA, Substance K, Neuromedin L); Neurokinin B;Neuropeptide K (NPK);Neuropeptide y; and C-terminal flanking peptide.
Substance P is expressesed primarilyin the small diameter primary sensoryfibers of the peripheral nervoussystem, and in the superficial dorsal horn of the spinalcord, the substantia nigra, and the medial amygdaloid nucleus of the central nervoussystem.