Defensins

Ubiquitous antimicrobial peptides with function as "endogenous antibiotics Occurs in all animal organisms and plants.

Defensins, like cathelicidins, belong to the group of antimicrobial peptides which play an essential role in innate immunity.

So far, 10 defensins have been described in humans. Beta-defensin-2 (HBD-2) and human beta-defensin-3 (HBD-3) are defensins that are formed in the skin and are broadly effective against bacteria and yeasts. The peptides are only produced "on demand".

Defensins consist of 33-47 amino acids and have 3 intramolecular disulfide bridges.

Defensins are expressed via NOD receptors.

Numerous occurrences on the skin and mucous membrane surfaces of mammals.

Granules of neutrophilic granulocytes consist of up to 30% defensins.

The body's own production of defensins increases during inflammatory reactions.

Presumed mechanism of action: Defensins have many cationic and hydrophobic amino acid residues. The positive charges react with negatively charged phospholipid groups of the external bacterial cell membrane. A so-called electrostatic "peptide carpet" is induced by these attractive forces, which leads to the formation of pores in the membrane and finally to their destruction.

1. Rieg S et al (2006) Generation of multiple stable dermcidin-derived antimicrobial peptides in sweat of different body sites. J Invest Dermatol. 126: 354-365
2. Wehkamp J et al (2007) Defensins and cathelicidins in gastrointestinal infections. Curr Opin Gastroenterol 23: 32-38