Endogenous Research Peptides

6 research peptides demonstrate endogenous properties. This collection covers their mechanisms, evidence base, and research applications.

Basic Science / Endogenous Reference | Antimicrobial / Immune

Beta-defensins are a family of small cationic antimicrobial peptides (36-45 amino acids, MW ~4-5 kDa) produced by epithelial cells throughout the body.

Mechanism: Beta-defensins are cationic amphipathic peptides containing three conserved disulfide bonds in a characteristic beta-sheet structure.

Basic Science / Endogenous Reference | Antimicrobial / Immune

Alpha-defensins are a family of small cationic antimicrobial peptides (29-35 amino acids, MW ~3.5-4.5 kDa) with three characteristic intramolecular disulfide bonds.

Mechanism: Alpha-defensins are cationic peptides with a triple-stranded beta-sheet structure stabilized by three disulfide bonds (Cys1-Cys6, Cys2-Cys4, Cys3-Cys5 connectivity).

Basic Science / Endogenous Reference | Antimicrobial / Immune

Histatin-5 is a 24-amino-acid histidine-rich cationic peptide (sequence: DSHAKRHHGYKRKFHEKHHSHRGY, MW ~3036 g/mol) found in human saliva.

Mechanism: Histatin-5 kills Candida albicans through a non-lytic, energy-dependent mechanism. The peptide binds to the fungal cell wall protein Ssa1/2 (a heat shock protein), is internalized via polyamine...

Well-Characterized Target / Approved Antagonists | Neuropeptide / Reference

Substance P is an 11-amino-acid neuropeptide (sequence: Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH2, MW ~1347.6 g/mol) belonging to the tachykinin family.

Mechanism: Substance P preferentially binds the neurokinin-1 receptor (NK1R), a G-protein-coupled receptor (Gq/11-coupled) expressed in the CNS, peripheral sensory neurons, immune cells, and GI tract.

Well-Characterized Neuropeptide / Active Drug Target | Neuropeptide / Reference

Neuropeptide Y (NPY) is a 36-amino-acid peptide (MW ~4271.7 g/mol) that is one of the most abundant and widely distributed neuropeptides in the mammalian brain.

Mechanism: NPY signals through five receptor subtypes (Y1, Y2, Y4, Y5, Y6), all Gi/o-coupled GPCRs that inhibit adenylyl cyclase and reduce cAMP. Y1 receptors mediate anxiolytic effects and vasoconstriction.

Active Research Target / No Approved Therapeutics | Neuropeptide / Reference

PACAP (Pituitary Adenylate Cyclase-Activating Polypeptide) is a neuropeptide that exists in two biologically active forms: PACAP-38 (38 amino acids, MW ~4534.3 g/mol) and PACAP-27 (27 amino acids, the N-terminal fragment).

Mechanism: PACAP signals through three receptors: PAC1 (PACAP-preferring, with >100-fold selectivity over VIP), VPAC1, and VPAC2 (shared with VIP).