Isolation and functional expression of a novel lipase gene isolated directly from oil-contaminated soil

A lipase gene SR1 encoding an extracellular lipase was isolated from oil-contaminated soil and expressed in Escherichia coli. The gene contained a 1845-bp reading frame and encoded a 615-amino-acid lipase protein. The mature part of the lipase was expressed with an N-terminal histidine tag in E. coli BL21, purified and characterized biochemically. The results showed that the purified lipase combines the properties of Pseudomonas chlororaphis and other Serratia lipases characterized so far. Its optimum pH and temperature for hydrolysis activity was pH 5.5-8.0 and 37°C respectively. The enzyme showed high preference for short chain substrates (556.3±2.8 U/µg for C10 fatty acid oil) and surprisingly it also displayed high activity for long-chain fatty acid. The deduced lipase SR1 protein is probably from Serratia, and is organized as a prepro-protein and belongs to the GXSXG lipase family.