Studies on psychrophilic enzymes to determine the structural features important for cold-activity have attracted increased attention in the last few years. This enhanced interest is due to the attractive properties of such proteins, i.e. a high specific activity and a low thermal stability, and thus, these enzymes constitute a tremendous potential for fundamental research and biotechnological applications. This review examines the impact of low temperatures on life, the diversity of adaptation to counteract these effects and gives an overview of the features proposed to account for low thermal stability and cold-activity, following the chronological order of the catalytic cycle phases. Moreover, we present an overview of recent techniques used in the analysis of the flexibility of a protein structure which is an important concept in cold-adaptation; an overview of biotechnological potential of psychrophilic enzymes and finally, a few frequently asked questions about cold-adaptation and their possible answers.
