Antimicrobuial peptides (AMPs) are cationic peptides that have the ability to adopt a structure in which hydrophobic and cationic amino acids are spatially organized in discrete sectors of the molecule ('winged' or 'amphipathic' design), by virtue of which they are both water soluble and capable of interacting strongly with biological membranes.

They are often attracted selectively to negatively charged microbial membranes, which they disrupt, as a primary antimicrobial mechansim. Translocation into the cell also permits them to interact with secondary targtes, thus interrupting vital methabolic processes. It is possible they may also act by interfering with external molecular targets on the microbial envelope, such as lipids involved in cell-wall synthesis or the autiolytic enzymes required for cellular dividion and remodelling, which would also contribute to cellular damage.

Host defence peptides (HDPs)s are natural, gene-encoded AMPs. They are evolutionarily ancient components of the innate immune system of many species. The many known HDPs are widely distributed throughout the animal and plant kingdoms, as well as in bacteria (>1000 eukaryotic peptides described).

AMPs and HDPs show an extraordinary molecular diversity, ranging in size from 12 to hundreds of residues, and belonging to several structural classes.



What are the functions of AMPs ?

Antibacterial activity, antifungal activity, in same cases antiviral, antiparasitic or anti-tumorour activity. Some also act as signal molecules for immune cells, being involved in chemotaxis or activation. AMPs are often effective against pathogens resistant to conventional antibiotics. Several AMPs have also been shown to be effective anti-endotoxin agents.