ACV synthetase: a unique member of the nonribosomal peptide synthetases family

Secondary metabolites (SMs) are bioactive molecules produced by fungi, bacteria and plants, that are not directly required for growth and reproduction of the organism. They generally mediate interactions with other organisms in the environment, and can provide selective advantages for the producer organisms. Because of their broad range of biological activities, SMs are being employed for many purposes, such as medicines, food flavouring and crop protection. Nonribosomal peptides (NRPs) are one of the main classes of SMs that are industrially produced today, with some notable examples such as the antibiotics penicillin and vancomycin, the immunosuppressant cyclosporin and the anticancer bleomycin. NRPs are synthesized by nonribosomal peptide synthetases (NRPSs), large multimodular enzymes that operate with a unique mechanism. In this thesis, we focused on the trimodular NRPS ACV synthetase (ACVS), which produces the tripeptide ACV. This small compound is particularly interesting from a biotechnological point of view, since it serves as a starting molecule for the synthesis of all β-lactam antibiotics (e.g., penicillin, cephalosporin, amoxicillin, etc.). We elucidated some of the fundamental aspects of the biosynthesis of ACV, and explored protein engineering strategies aimed at producing modified peptides. In the future, this will enable the production of novel penicillin antibiotics in a simple and efficient manner. Further, it can replace the costly and laborious chemical processes that are employed to synthesize semi-synthetic penicillin today, helping to push the antibiotics industry towards a bio-based economy.