MOLECULAR ADAPTATION TO COLD OF AN ANTARCTIC BACTERIAL LIPASE

The lipase from the Antarctic psychrophilic bacterium Psychrobacter im mobilis B10 shows a very limited thermal stability when compared to th e lipase from a mesophilic strain of Pseudomonas aeruginosa. The therm al dependence of its activity is shifted by at least 30 degrees C towa rds low temperatures and its activation energy is reduced by a factor of 2. The three-dimensional model of the P. immobilis lipase reveals s everal features typical of cold-adapted enzymes: a very low proportion of arginine residues as compared to lysines, a low content in proline residues, a small hydrophobic core, a very small number of salt bridg es and of aromatic-aromatic interactions. All these properties should confer on the enzyme a more flexible structure, in accord with its low activation energy and its low thermal stability.