Marked enhancement of Acinetobacter sp. organophosphorus hydrolase activity by a single residue substitution Ile211Ala

Abstract

The activity of organophosphorus hydrolase (OPH) that catalyzes the hydrolysis of neurotoxic organophosphates (OPs) was reported to evolve from lactonase. In this study, a putative OPH from Acinetobacter sp. (AbOPH) exhibited high lactonase activity with latent OPH activity. Sequence alignment and phylogenetic tree analysis revealed the unique status of AbOPH in evolution. The crystal structure of AbOPH was determined at 2.0 Å resolution and a semi-rational design was performed to enhance the OPH activity of AbOPH through a consensus sequence approach. Compared with wild-type AbOPH, which exhibited undetectable activity toward methyl-parathion (MP), the best variant AbOPHI211A showed markedly improved catalytic efficiency (1.1 μmol min−1 mg protein −1 ) toward MP. Docking studies suggested that the mutation Ile211Ala affects substrate recognition and stabilizes substrate conformation. This result presents the emergence of new enzyme function by a simple mutation strategy and confirms the high possibility that OPH was evolved from its lactonase ancestor.