Human Beta-Defensin 3 | Encyclopeptide

Chemical Identity

Property	Value
Chemical Formula	C183H286N52O52S8
Molecular Weight	5158.04 g/mol
CAS Number	394649-84-0
IUPAC Name	Beta-defensin 3 (DEFB103A gene product)
Peptide Class	Beta-Defensin
Disulfide Bonds	3 (conserved beta-defensin pattern)

Structure

Human beta-defensin 3 (hBD-3) is a 45-amino acid cationic peptide with three conserved intramolecular disulfide bonds in the canonical beta-defensin pattern (Cys1-Cys5, Cys2-Cys4, Cys3-Cys6). It contains eight positively charged residues (five arginines, three lysines), giving it a net charge of +11, higher than hBD-1 or hBD-2. This high cationic charge density contributes to its superior antimicrobial potency.

Mechanism of Action

hBD-3 kills microbes through multiple mechanisms:

Membrane disruption: Electrostatic binding to anionic bacterial membranes, forming multimeric pores
Broad-spectrum activity: Unlike hBD-2, hBD-3 is equally potent against gram-positive (S. aureus, MRSA) and gram-negative bacteria, as well as Candida albicans
Chemotaxis: Activates CCR6 on dendritic cells and T cells
MRSA activity: Effective against methicillin-resistant Staphylococcus aureus at low micromolar concentrations

Biological Functions

hBD-3 is constitutively expressed at epithelial surfaces and further induced by microbial challenge:

Expression sites: Tonsillar epithelium, skin, airway, oral mucosa, heart, liver, placenta
Induction: TLR2-mediated signaling, IFN-gamma, IL-22, and microbial products
Synergy: Works synergistically with hBD-2, LL-37, and conventional antibiotics

Clinical Relevance

hBD-3 is a promising candidate for development as a topical anti-infective agent. Its activity against MRSA and vancomycin-resistant enterococci makes it valuable for combating multidrug-resistant infections. Applications under study include wound dressings, surgical implant coatings, and treatment of chronic rhinosinusitis. Reduced defensin expression in atopic dermatitis skin correlates with increased infection susceptibility.

Safety and Side Effects

As an endogenous human peptide, hBD-3 has excellent safety at physiological concentrations. Some hemolytic activity has been reported at supraphysiological concentrations (>50 microM). Local inflammatory responses may occur due to chemotactic properties. Therapeutic applications focus on topical delivery to minimize systemic exposure.

References

Harder, J., et al. (2001). Isolation and characterization of human beta-defensin-3, a novel human inducible peptide antibiotic. Journal of Biological Chemistry, 276, 5707-5713.
García, J.R., et al. (2001). Identification of a novel, multifunctional beta-defensin (human beta-defensin 3) with specific antimicrobial activity. Cellular and Molecular Life Sciences, 58, 1147-1159.