In nonribosomal biosynthesis of custom peptide synthesis by multimodular synthetases, amino acid monomers are activated by the adenylation domains of the synthetase and loaded onto the adjacent carrier protein domains as thioesters, then the formation of custom peptide synthesis and translocation of the growing chain are effected by the synthetase's condensation domains. Whether the condensation domains have any editing function has been unknown.
Synthesis of aminoacylcoenzyme A (CoA) molecules and direct enzymatic transfer of aminoacylphosphopantetheine to the carrier domains allow the adenylation domain editing function to be bypassed. This method was used to demonstrate that the first condensation domain of tyrocidine synthetase shows low selectivity at the donor residue (D-phenylalanine) and higher selectivity at the acceptor residue (L-proline) in the formation of the chain-initiating D-Phe-L-Pro dipeptidyl-enzyme intermediate.
For the development and production of pharmacologically important compounds based on natural scaffolds simple and effective techniques that can combine chemistry, genetics and molecular biology are indispensable. The NRPSs can provide such interesting tools to generate and modify novel products. The recently gained structural and mechanistic information on NRPSs have made this class of multienzymes a powerful native tool box that would help to achieve this goal. Rearrangements of domains and modules in combination with the elucidation of chemoenzymatic reactions highly increases the potential of these special enzymes.