Thermostable lipases from extremely radioresistant bacterium Deinococcus radiodurans: cloning, expression, and biochemical characterization.

A search for lipases was conducted in the radiophile of Deinococcus radiodurans R1. Four putative lipase genes, encoding DR0334, DR2078, DR1485, and DR2522, were cloned and expressed in Escherichia coli. The recombinant enzymes were subsequently purified and characterized. The results showed DR0334 and DR2078 had the ability to hydrolyze long-chain length p-nitrophenyl esters (C12-C16), while DR1485 and DR2522 hydrolyzed short- and medium-chain length p-nitrophenyl esters (C2-C10). DR0334, DR1485, DR2078, and DR2522 showed optimum pH at 8.5, and optimum temperature at 40, 50, 60, and 60 °C, respectively. DR0334 almost lost its whole activity after 60 min pretreatment at 60 °C, while DR1485, DR2078, and DR2522 retained more than 70% of their original activities after 6 h incubation at 80 °C. The activities of DR2078, DR1485, and DR2522 were enhanced by Mg(2+) , Ba(2+) , and Mn(2+) , but strongly inhibited by EDTA. Nevertheless, DR2078, DR1485, and DR2522 showed moderate stability in organic solvents and detergents. Phylogenetic analysis revealed that DR0334 and DR2078, respectively belong to family IV and family IX, while each of DR1485 and DR2522 forms a new separate branch. The unique properties of DR2078, DR1485, and DR2522, thermostability and organic solvent tolerance, make them useful in industrial applications.