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Recombinant expression and characterisation of a lipase from the Antarctic zooplankton Salpa thompsoni

Cold marine environments are abundant on earth and represent a rich resource for low temperature enzymes. Here we apply in silico bioprospecting methods followed by in vitro expression and biochemical analyses to characterise a novel low temperature lipase from the Antarctic tunicate Salpa thompsoni. A 586 amino acid pancreatic lipase-like gene was identified from S. thompsoni transcriptomic data, expressed as a hexahistadine fusion protein in Escherichia coli at 10°C and purified by affinity chromatography. Hydrolysis of the synthetic substrate ρ-nitrophenyl butyrate (PNPB) showed that this recombinant protein has optimal activity at 20 °C and pH 7, and a specific activity of 3.16 U/mg under this condition. Over 60% of enzyme activity was maintained between 15 to 25 °C, with a sharp decrease outside this range. These results are indicative of cold active psychrophilic enzyme activity. A meta-analysis of lipase activities towards PNPB showed that the novel S. thompsoni lipase displays a higher activity at lower temperatures relative to previously characterised enzymes. The work demonstrates a methodology for conversion of transcriptomic to in vitro expression data for the discovery of new cold-active biocatalysts from marine organisms.