Molecular biology of peptide and polyketide biosynthesis in cyanobacteria

Cyanobacteria produce numerous and structurally diverse secondary metabolit es, in particular nonribosomal peptide and polyketide structures. Various b ioactivities could be assigned to these compounds, and some may prove usefu l either for development into commercial drugs or as biochemical research t ools. Microcystin, a worldwide common cyanobacterial hepatotoxin, was the f irst metabolite whose nonribosomal biosynthesis could be confirmed by knock -out mutagenesis. The microcystin synthetase complex consists of peptide sy nthetases, polyketide synthases, and hybrid enzymes, and reveals a number o f novel enzymatic features, signifying the potential of cyanobacterial bios ynthetic systems for combinatorial biochemistry. Recent studies have shown the presence of peptide synthetase genes and polyketide synthase genes with in a number of cyanobacterial genomes. This knowledge may be very valuable for future, screening projects aimed at the detection of new bioactive comp ounds.