Molecular cloning and characterization of a novel acetylalginate esterase gene in alg operon from Sphingomonas sp. MJ-3.

A novel acetylalginate esterase (AcAlgE) gene was cloned and characterized from the genomic DNA library of Sphingomonas sp. MJ-3. A putative gene encoding AcAlgE protein of 292-residue precursor protein with 20-amino acid signal peptide was identified in the alg operon. The deduced AcAlgE protein has GDSL-like consensus motif and shares a highest sequence identity (51%) with GDSL family lipolytic protein from Pseudoxanthomonas suwonensis. Enzymatic assays with bacterial acetylalginate as the substrate showed that the recombinant AcAlgE protein possesses deacetylation activity. The optimal temperature and pH for the AcAlgE were 22 °C and pH 6.5 (citrate buffer), respectively. The recombinant AcAlgE protein catalyzed deacetylation of acetylalginate with release of acetate. The resulting de-acetylated alginate was readily degraded by alginate lyases, indicating that the recombinant AcAlgE enhanced the subsequent degradation of acetylalginate by alginate lyases. The recombinant AcAlgE can play an important role in the degradation of acetylated alginate such as mucoidal acetylalginate in cystic fibrosis patient.