Cloning and expression of a novel esterase gene cpoA from Burkholderia cepacia

Abstract

Aims: To screen and clone a novel enzyme with specific activity for the resolution of (R)-β-acetylmercaptoisobutyrate (RAM) from (R,S)-β-acetylmercaptoisobutyrate [(R,S)-ester]. Methods and Results: A micro-organism that produces a novel esterase was isolated and identified as the bacterium Burkholderia cepacia by using the analysis of cellular fatty acids, Biolog automated microbial identification/characterization system, and 16S rRNA gene sequence analysis. A novel esterase gene was cloned from the chromosomal DNA of B. cepacia and was designated as cpoA. The cpoA encodes a polypeptide of 273 amino acids which shows a strong sequence homology with many bacterial nonhaeme chloroperoxidases. In addition, a typical serine-hydrolase motif, Gly-X-Ser-X-Gly, and the highly conserved catalytic triad, Ser95, Asp224, and His253, were identified in the deduced amino acid sequence of cpoA by multiple sequence alignment. Conclusion: The cpoA cloned from B. cepacia encodes a novel esterase which is highly related to the nonhaeme chloroperoxidases. Significance and Impact of the Study: This is the first report that describes the isolation and cloning of a serine esterase gene from B. cepacia, which is useful in the chiral resolution of (R,S)-ester. The cloned gene will allow additional research on the bifunctionality of the enzyme with esterase and chloroperoxidase activity at the structural and functional levels.