These environments comprise, among others, the Antarctic, Arctic and mountain regions, as well as the deep-sea waters that cover three-quarters of the planet surface. When one considers the vast extent of permanently cold habitats, most parts of our planet are exposed to low temperatures, often below 0 ☌. Due to their attractive properties, i.e., a high specific activity and a low thermal stability, these enzymes constitute a tremendous potential for fundamental research and biotechnological applications.Ĭold-adaptation, Psychrophiles, Extremophiles, Enzyme kinetics, Enzyme activity, Flexibility concept 1 Introduction The emerging picture suggests that psychrophilic enzymes are characterized by an improved flexibility of the structural components involved in the catalytic cycle, whereas other protein regions, if not implicated in catalysis, may be even more rigid than their mesophilic counterparts.
Thanks to recent advances provided by X-ray crystallography, structure modelling, protein engineering and biophysical studies, the adaptation strategies are beginning to be understood. Thermal compensation in these enzymes is reached, in most cases, through a high catalytic efficiency associated, however, with a low thermal stability. Psychrophiles have evolved by producing, among other peculiarities, “cold-adapted” enzymes which have the properties to cope with the reduction of chemical reaction rates induced by low temperatures. These organisms, hosts of permanently cold habitats, often display metabolic fluxes more or less comparable to those exhibited by mesophilic organisms at moderate temperatures. The substrate concentration that gives you a rate that is halfway to V m a x V_ V m a x V, start subscript, m, a, x, end subscript, which depends on enzyme concentration, K m K_m K m K, start subscript, m, end subscript is always the same for a particular enzyme characterizing a given reaction (although the "apparent," or experimentally measured, K m K_m K m K, start subscript, m, end subscript can be altered by inhibitors, as discussed below).In the last few years, increased attention has been focused on a class of organisms called psychrophiles.
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