Evolution of Phosphotriesterases (PTEs): How bacteria can acquire new degradative functions

The promiscuity of enzymes has often been considered a vestige activity based on the broad substrate spectrum of their progenitors. As such, divergent enzymes can be used as a fingerprint to track their evolutionary history. In the presence of structural mimics of active site or binding site ligands and assisted by mutations in the associated binding site, this promiscuity contributes to acquisition of new catalytic functions. This phenomenon is often referred to as substrate-assisted gain-of-function and helps soil microbes to thrive on re-calcitrant xenobiotic molecules, hitherto unfamiliar to the microbial world. This review describes the evolution of organophosphorous hydrolases, which potentially and originally functioned as quorum-sensing ‘quenching’ lactonases and highlights their remarkable horizontal mobility within diverse bacterial species