ABSTRACT
Many peptide antibiotics have been described in the past 55 years (Hancock et al., 1995; Kleinkauf and von Dohren, 1988; Perlman and Bodansky, 1971). These can be fit into two broad classes, nonribosomally synthesized peptides, such as the gramicidins, polymyxins, bacitracins, glycopeptides etc. and ribosomally synthesized (natural) peptides. The former are synthesized, usually in bacteria, by large complexes of modular enzymes termed peptide synthetases, and are often substantially modified. In contrast, the latter are produced as pro-peptides, using the normal process of protein synthesis. They are found in all species of life (including bacteria) as a major component of the natural host defense molecules of these species.
