A Thermostable Bacterial Metallohydrolase that Degrades Organophosphate Plasticizers

Abstract

A cyclase-phosphotriesterase (C-PTE) from Ruegeria pomeroyi DSS-3 has recently been identified for its capacity to detoxify several organophosphate compounds. However, several aspects of this enzyme remain unexplored, such as its activity with industrial organophosphates, its molecular structure, and its thermostability. In this work, the crystal structure of C-PTE is reported, which is solved to 2.3 Å resolution, providing insight into the enzyme's mechanism of action, revealing a binuclear Zn²⁺ active site and distant similarity to other phosphotriesterases from the amidohydrolase superfamily. It is shown that C-PTE catalyzes the hydrolysis of the OP plasticizers triphenyl phosphate (TPhP) and tris(2-chloropropyl) phosphate (TCPP), albeit with low efficiency, but not the sterically bulkier tri-o-tolyl phosphate (ToTP). Finally, it is demonstrated that, even though Ruegeria pomeroyi DSS-3 is not a thermophile, C-PTE exhibits remarkable thermostability and retains structure up to 90 °C. Overall, these findings advance the understanding of C-PTE, suggesting that it is a good candidate for engineering owing to its thermostability and that it could contribute to bioremediation strategies to reduce the impact of pollution by industrial organophosphates.