The extensive characterization of CDPSs is ongoing in the lab. Studies have already shown that CDPSs divert aminoacylated-tRNAs (aa-tRNAs) from their canonical role in ribosomal protein synthesis to use them as substrates for catalyzing the formation of various cyclodipeptides. We also demonstrated the high structural similarity of CDPSs with class I-aminoacyl-tRNA synthetases (AARSs), the enzymes that catalyze the loading of amino acids on their corresponding tRNAs to form aa-tRNAs.
We elucidated the catalytic mechanism used by CDPSs: it proceeds through the successive formation of two covalent intermediates, an aminoacyl-enzyme and a dipeptidyl-enzyme (Figure 3). We also identified first determinants of CDPS specificity and this work is currently ongoing in the lab.
We are also interested in cyclodipeptide-modifying enzymes that are associated with CDPSs in DKP biosynthetic pathways. For example, we studied CYP121, a cytochrome P450 of Mycobacterium tuberculosis, which has been described as essential to the viability of the pathogen. Our work led to the identification of the substrate and the product of CYP121 as well as to the determination of its substrate and reaction specificity. In addition, as CYP121 is a potential new therapeutic target, we developed substrate analogues that selectively inhibit CYP121.