Characterization of a novel thermophilic pyrethroid-hydrolyzing carboxylesterase from Sulfolobus tokodaii into a new family

A novel gene ST2026 encoding a putative carboxylesterase from the thermophilic crenarchaeota Sulfolobus tokodaii (named EstSt7) was cloned and functionally overexpressed in Escherichia coli. The recombinant enzyme was purified to homogeneity after heat treatment, Ni-NTA affinity and Superdex-200 gel filtration chromatography. EstSt7 showed maximum activity at 80 °C over 30 min and had a half-life of 180 min at 90 °C. Its enzymatic activity was stable in the pH range of 8.0–10.0 with an optimum at 9.0. The enzyme exhibited significant esterase activity toward various p-nitrophenyl esters and the most preferable substrate was p-nitrophenyl butyrate (kcat/Km of 246.3 s−1 mM−1). In addition, EstSt7 showed high activity and stability against organic solvents (20% and 50% v/v) and detergents (1% and 5% v/v). Furthermore, EstSt7 could efficiently hydrolyze a wide range of synthetic pyrethroids including fenpropathrin, permethrin, cypermethrin, cyhalothrin, deltamethrin and bifenthrin, which makes it a potential candidate for the detoxification of pyrethroids for the purpose of biodegradation. Sequence alignment, phylogenetic analysis and comparison of the conserved motif reveal that this novel carboxylesterase EstSt7 should be grouped into a new bacterial lipase and esterase family.