Cloning and fusion expression of a cold-active lipase from marine Antarctic origin

Antarctic seawater bacteria producing extracellular lipolytic enzymes with activity at low temperatures were isolated. The most promising strain was selected to perform a 16S characterization which identified it as a Psychrobacter sp. The genomic DNA of this bacterium was used for a PCR screening using primers obtained from multiple sequence alignments of lipases belonging to the hormone sensitive lipase (HSL) group of the prokaryotic species. This allowed cloning and sequencing of the DNA that partially encodes a novel lipase protein (240 bp, 80 aa). Subsequently the complete gene was obtained by a genome-walking technique. An open reading frame of 1293 bp was found, which encodes for a polypeptide of 431 amino acids, and presents 89% identity with lipase 2 from Moraxella TA144 previously described; however its properties are very different. The promoter and downstream sequences of this gene were also obtained. The new lipase gene was cloned into expression vector pMAL-c2E and integrated into E. coli TB1. A recombinant fusion protein (MBP-lipase) with a molecular weight of 90 kDa was produced and purified which showed lipolytic activity. The optimum temperature for this fusion lipase was 20 °C at pH 8.0, and the activation energy was 5.5 kcal/mol between 5 and 20 °C at the same pH.