Human defensins.
Antimicrobial peptides are small, cationic, amphiphilic peptides of 12-50 amino acids with microbicidal activity against both bacteria and fungi. The eukaryotic antimicrobial peptides may be divided into four distinct groups according to their structural features: cysteine-free alpha-helices, extended cysteine-free alpha-helices with a predominance of one or two amino acids, loop structures with one intramolecular disulfide bond, and beta-sheet structures which are stabilised by two or three intramolecular disulfide bonds. Mammalian defensins are part of the last-mentioned group. The mammalian defensins can be subdivided into three main classes according to their structural differences: the alpha-defensins, beta-defensins and the recently described theta-defensins. Mammalian alpha-defensins are predominantly found in neutrophils and in small intestinal Paneth cells, whereas mammalian beta-defensins have been isolated from both leukocytes and epithelial cells. Recently, two novel human beta-defensins, human beta-defensin-3 (HBD-3), and human beta-defensin-4 (HBD-4) have been discovered. Similar to HBD-1 and HBD-2, HBD-3 has microbicidal activity towards the Gram-negative bacteria (Pseudomonas aeruginosa, Escherichia coli) and the yeasts Candida albicans and Malassezia furfur. In addition, HBD-3 kills Gram-positive bacteria such as Streptococcus pyogenes or Staphylococcus aureus, including multi-resistant S. aureus strains, and even vancomycin-resistant Enterococcus faecium. In contrast to HBD-1 and HBD-2, significant expression of HBD-3 has been demonstrated in non-epithelial tissues, such as leukocytes, heart and skeletal muscle. HBD-4 is expressed in certain epithelia and in neutrophils. Its bactericidal activity against P. aeruginosa is stronger than that of the other known beta-defensins. Here we present an overview of human antimicrobial peptides with some emphasis on their antifungal properties.
Schneider
Josef Johann
JJ
Klinik und Poliklinik für Dermatologie und Allergologie, Ludwig-Maximilians-Universität München, Frauenlobstrasse 9-11, 80337 Munich, Germany. josefschneider@gmx.de
Unholzer
Angela
A
Schaller
Martin
M
Schäfer-Korting
Monika
M
Korting
Hans Christian
HC
D000818:Animals; D000890:Anti-Infective Agents / Q000145:classification / Q000378:metabolism; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology; D002626:Chemistry, Pharmaceutical; D023082:Defensins / Q000145:classification / Q000378:metabolism*; D006801:Humans
D000890:Anti-Infective Agents; D023181:Antimicrobial Cationic Peptides; D023082:Defensins