Did psychrophilic enzymes really win the challenge?

Organisms living in permanently cold environments, which actually represent the greatest proportion of our planet, display at low temperatures metabol ic fluxes comparable to those exhibited by mesophilic organisms at moderate temperatures. They produce cold-evolved enzymes partially able to cope wit h the reduction in chemical reaction rates and the increased viscosity of t he medium induced by low temperatures. In most cases, the adaptation is ach ieved through a reduction in the activation energy, leading to a high catal ytic efficiency, which possibly originates from an increased flexibility of either a selected area of or the overall protein structure. This enhanced plasticity seems in return to be responsible for the weak thermal stability of cold enzymes. These particular properties render cold enzymes particula rly useful in investigating the possible relationships existing between sta bility, flexibility, and specific activity and make them potentially unriva led for numerous biotechnological tasks. In most cases, however, the adapta tion appears to be far from being fully achieved.