The relationships between temperature, catalytic activity, regulatory properties and stability will be investigated in a group of three enzymes chosen as model systems for the study of psychrophilic (cold-loving) bacteria isolated from the Antarctic Ocean by H. Rüger and N. Glansdorff. The enzymes are the carbamoyltransferases of aspartate (one of the three or four best known allosteric enzymes), of ornithine and carbamoylphosphate synthetase. In order to investigate the relationships between structure and function in these enzymes we shall determine their kinetic, allosteric and thermal profiles, clone the corresponding genes, sequence them and proceed to a thorough comparison with the mesophilic and thermophilic homologs. Experiments of in vitro mutagenesis will be performed to test the hypothesis formulated on the basis of these investigations.
