The "extremozymes" from thermophilic microorganisms are usually optimally active between 60°C and 80°C. The "extremozymes" offer unique biotechnological advantages over mesophilic (optimally active at 25-50°C) or psychrophilic enzymes (optimally active at 5-25°C). Once expressed in mesophilic hosts thermophilic enzymes preserve most of their features, being easily purified by heat treatment, showing high resistance to chemical denaturants, and maintaining their enzymatic activity at high temperatures. In this chapter, we will discuss the discovery of extremophilic carbonic anhydrases (CAs) belonging to the α-, β-, and γ-classes, and the possibility for utilizing them in different biotechnological and biomedical applications, such as the carbon dioxide capture and sequestration process (CCS). We also propose the use of "extremo-CAs" for artificial respiration systems as well as for selective biosensors for metal ions, until now implemented with heat-labile CAs.
