Characterization of a Novel Family IV Esterase Containing a Predicted CzcO Domain and a Family V Esterase with Broad Substrate Specificity from an Oil-Polluted Mud Flat Metagenomic Library

Two novel esterase genes, est2L and est4L, were identified from a previously constructed metagenomic library derived an oil-polluted mud flat sample. The encoded Est2L Est4L composed of 839 267 amino acids, respectively, without signal peptides. was unique fusion type protein two domains: domain the CzcO superfamily, associated with cationic diffusion promoter CzcD, acetylesterase belonging to family IV conserved motifs, such as HGG, GXSAG, GXPP. first fused domain. belonged V GXS, GXSMGG, PTL motifs. Native found be in dimeric tetrameric forms, respectively. showed highest activities at 60 °C 50 °C, pH 10.0. preferred short length substrates, especially p-nitrophenyl (pNP)-acetate, moderate butyrylcholinesterase activity, whereas activity pNP-decanoate had broad specificity. Significant effects not observed Co2+ Zn2+, although contains CzcD. high stabilities 30% methanol 1% Triton X-100. These enzymes could used for variety applications, detergent mining processing under alkaline conditions.