HUMAN DEFENSIN PEPTIDES WITH ANTIMICROBIAL PROPERTIES: AN OVERVIEW

Human defensin peptides with antimicrobial properties are classified under antimicrobial peptides (AMPs). They are produced by neutrophils and epithelial cells and involved in innate immunity through killing of microbial pathogens or neutralizing bacterial toxins and adaptive immunity by serving as chemo attractants and activators of immune cells. They all are 29-35 amino acids peptides, invariably cationic in nature and belongs to β sheet structure with two or three intra molecular disulfide bonds. Many of them attack their target cells by permeabilizing the cell membrane. They can be roughly categorized into three main classes according to their structural differences: the α defensins, β defensins and θ defensins. Most of the known human defensin peptides with antimicrobial functions have been identified and studied during the last 15 years. As a result of these studies, new knowledge has been acquired into biology and biochemistry. It has become evident that these peptides may be developed into useful antimicrobial additives and drugs. The use of some defensin mimetic peptide as replacement for clinical antibiotics is promising. This review focuses on the current status of some of the main types of human defensin AMPs produced by neutrophils and epithelial cells and discusses its mode of action, the novel antimicrobial functions, molecular characterization, new developments, e.g. recombinant DNA production of defensins in bacteria and transgenic plants, novel applications related to these peptides, and future research paradigms.