[Expression and characterization of lipase LpsA2 from Streptomyces avermitilis].

Objective: We expressed the lipase gene lpsA2 from Streptomyces avermitilis in Escherichia coli and characterized the enzymatic properties of LpsA2.

Methods: We extracted the genomic DNA of S. avermitilis and amplified lpsA2 gene by PCR with specific primers. We then expressed lpsA2 gene in E. coli and determined the enzymatic properties of LpsA2. We also analyzed the evolutionary relationship between LpsA2 and lipase family by using phylogenetic tree based on the alignment of amino acid sequences.

Results: According to the alignment of amino acid sequences, we found that LpsA2 had the active site (Ser130-Asp221-His253) which was consistent with the typical characteristics of lipases that their active centers always consisted of Ser, His and Asp, and Ser always located in the conserved five peptide structure (Gly128-His129-Ser130-Gln131-Gly132). We constructed the evolutionary tree and found that LpsA2 belonged to Subfamily I.7 of lipase Family I. Furthermore, the optimal pH and temperature of LpsA2 were pH 8.0 and 50 degrees C, respectively. The best substrate of LpsA2 was p-nitrophenol myristate. The activation energy (Ea) of LpsA2 between 10 degrees C and 50 degrees C was 6.3 kcal/mol. The enzyme activity of LpsA2 was increased to 250% or above by 1 mmol/L Co2+, Hg2+ and Zn2+, respectively. The activity was also elevated to 110.7% and 138.0% by 15% dimethylformamide and dimethyl sulfoxide, and 352.7% and 189.7% by 0.1% and 1% Span-20, respectively.

Conclusion: The enzymatic properties of LpsA2 from S. avermitilis were characterized that may provide the fundament to the screening of bio-engineered bacteria and the industrial applications in food processing and drug synthesis.