Abstract
A esterase gene was characterized from a halophilic bacterium Chromohalobacter canadensis which was originally isolated from a salt well mine. Sequence analysis showed that the esterase, named as EstSHJ2, contained active site serine encompassed by a conserved pentapeptide motif (GSSMG). The EstSHJ2 was classified into a new lipase/esterase family by phylogenetic association analysis. Molecular weight of EstSHJ2 was 26kDa and the preferred substrate was p-NP butyrate. The EstSHJ2 exhibited a maximum activity at 2.5M NaCl concentration. Intriguingly, the optimum temperature, pH and stability of EstSHJ2 were related to NaCl concentration. At 2.5M NaCl concentration, the optimum temperature and pH of EstSHJ2 were 65 ℃ and pH 9.0, and enzyme remained 81% active after 80 ℃ treatment for 2h. Additionally, the EstSHJ2 showed strong tolerance to metal ions and organic solvents. Among these, 10mMK+, Ca2+ , Mg2+ and 30% hexane, benzene, toluene has significantly improved activity of EstSHJ2. The EstSHJ2 was the first reported esterase from Chromohalobacter canadensis, and may carry considerable potential for industrial applications under extreme conditions.
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