Thermal stabilization of psychrophilic enzymes: A case study of the cold-active hormone-sensitive lipase from Psychrobacter sp. TA144

Cold-adapted enzymes possess high specific activity at low and moderate temperatures with respect to their mesophilic and thermophilic homologues; it is accepted that they have a less rigid and more flexible structure in the region surrounding the active site. However the low stability of such molecules could represent the main barrier for their application in some industrial bioprocesses. The aim of this paper was to investigate the ability of the naturally occurring osmolytes to increase the thermal stability and the specific activity of the cold-active lipase from Psychrobacter sp. TA144 (PsyHSL), which belongs to the Hormone-Sensitive Lipase group. The effect of trimethylamine N-oxide (TMAO), betaine and L-proline addition on the activity and thermal stability of PsyHSL was investigated by means of biochemical and biophysical techniques. It turned out that in the presence of 3M TMAO the enzyme specific activity enhanced up to 250% at 50 °C, while the addition of 1M TMAO increased the thermostability five-fold at 45 °C. Our experiments demonstrated that, even in the case of a psychrophilic enzyme, osmoprotectants, particularly TMAO, addition may be considered an efficient strategy to improve the protein thermal stability and specific activity at higher temperatures-