Tachykinins are active peptides which excite neurons, evoke behavioral responses, are potent vasodilators and secretagogues, and contract (directly or indirectly) many smooth muscles. The substance P form is cleaved at Pro-2 by the prolyl endopeptidase FAP (seprase) activity (in vitro). Substance P is also cleaved and degraded by Angiotensin-converting enzyme (ACE) and neprilysin (MME). Belongs to the tachykinin family.