Cold-adapted enzymes: fundamentals and applications

Abstract

Habitats of permanently cold temperature have been successfully colonised by a wide variety of psychrophilic organisms which display metabolic fluxes similar to those of their mesophilic homologs at their respective environmental temperatures. The ability to not only survive, but to thrive, at low temperatures indicates a vast array of adaptive features, notably at the level of the membranes, transcription and translation processes, protein folding and enzyme activities. Of particular importance is the production of cold-adapted enzymes which have the ability to cope with the reduction of chemical reaction rates induced by low temperatures. Indeed, these enzymes are found to be characterised by a high activity at low to moderate temperatures as well as a decreased stability of their molecular edifice. The current consensus is that this optimisation of enzyme activity is mainly achieved through an increase in the flexibility of specific regions (those involved in the catalytic cycle) or of the whole protein, thereby allowing for the molecular motions necessary for activity in the low energy environment but also leading to the observed low stability. Here, the current knowledge and recent advances in the understanding of the molecular adaptations of psychrophilic enzymes will be presented. Furthermore, applied aspects of these enzymes, with examples of their current uses in industry, will be discussed and the importance of extremophilic environments as sources of novel enzymes of fundamental and industrial importance will be highlighted.