Characterization and a point mutational approach of a psychrophilic lipase from an arctic bacterium, Bacillus pumilus

Abstract

A bacterium with lipolytic activity was isolated from the Chukchi Sea within the Arctic Ocean. The lipase BpL5 from the isolate, Bacillus pumilus ArcL5, belongs to subfamily 4 of lipase family I. The optimum pH and temperature of the recombinant enzyme BpL5, as expressed in Escherichia coli, were 9.0 and 20 C, respectively. The enzyme retained 85 % of its activity at 5 C. There was a significant difference between temperatures for maximal activity (20 C) and for protein denaturation (approx. 45 C). The enzyme preferred middle-chain (C8) p-nitrophenyl substrates. Two mutants, S139A and S139Y, were rationally designed based on the 3Dstructure model, and their activities were compared with that of the wild type. The both mutants showed significantly improved activity against tricaprylin.