Production of secondary metabolites is one of the industrially important features of bacteria, such as actinomycetes and myxobacteria. Various secondary metabolites produced by bacteria have been developed as antibiotics, antitumor drugs and immunosuppressive drugs. Therefore, bacterial secondary metabolites have an important role in the development of novel medicines. Secondary metabolites usually comprise various chemical moieties, such as polyketide backbones, amino acid derivatives and sugars. Many enzymes are involved in the synthesis of secondary metabolites. Polyketide synthase (PKS) and non-ribosomal peptide synthetase (NRPS), which catalyze the elongation of polyketides and synthesis of oligopeptides, respectively, are the major enzymes of secondary metabolite synthesis. Enzymes responsible for the synthesis of other constitutive compounds, such as sugars, are often encoded by genes adjacent to PKS and NRPS genes. Through further tailoring events, such as glycosylation, alkylation and oxidation, structurally diverse and complex metabolites are finally synthesized. In addition, the production and transportation of secondary metabolites are strictly regulated by transcriptional regulators and transporters.
(Ichikawa et al., 2013) DoBISCUIT: a database of secondary metabolite biosynthetic gene clusters. Nucleic Acids Res.