Extremozymes

Extremozymes—enzymes that can tolerate relatively harsh conditions, suggested as catalysts for complex organic synthesis of fine chemicals and pharmaceuticals (Govardhan and Margolin, 1995). 

In the recent past extremozymes, e.g. bacterium Pyrococcas furiosus the flaming fireball, which can work at temperatures even above 100 C, have opened up new vistas (Rice, 1998). 

Extremozymes, enzymes from thermophilic bacteria, have become important in synthetic chemistry. 

Escherichia coli (Niehaus, 1999). Whereas halophiles (Margesin, 2001) and piezo-philes (Abe, 2001) have attracted attention, the main aspect of interest for biotechnological application remains thermal stability, focusing interest on thermophiles or even hyperthermophiles. Increase in temperature has a significant influence on the bioavailability and solubility of organic compounds (not on the solubility of Oz, however, which is nearly zero at extremophilic temperatures ). Current applications of extremozymes include ... 

Hough, D.W. and Danson, M.J. Extremozymes. (1999) Curr Opin Chem Biol, 3,39-46. 

Gomes, J. and Steiner, W., The biocatalytic potential of extremophiles and extremozymes, Food Technol. Biotechnol. 42 279-286 (2004). 

The DNA fragments are expressed (proteins are made from the genes contained in the fragments) most commonly using E. coli. Interestingly, even though E. coli must be cultured under the mild conditions necessary for them to survive, the extremozymes formed seem to have their characteristic catalytic activities, indicating that they have the same structures as when they are formed in their native extreme conditions. 

The mixtures of extremozymes produced by the expression process are then tested to see if they have catalytic activity for the industrial processes of interest. If a given mixture shows catalytic activity, it is then usually subjected to random DNA mutagenesis or molecule breeding to see whether random evolution of the enzymes will lead to improved activities. 

For many years, one way to solve these drawbacks has been the identification and isolation of new biocatalysts with the desired characteristics. The most common procedure for isolation and identification of biocatalysts has also been applied to microbial populations living in harsh environments such as hot springs, abyssal hot vents or geothermal power plants. These microorganisms, known as extremophiles can be foimd in environments of extreme temperature, ionic strength, pH, pressure, metal concentrations or radiation levels. These natural reservoirs of extremozymes directly offer new activities and extreme stabilities but these microorganisms also offer novel metabolic pathways. Table 10.11 summarizes the identified extremoz5mies found in some extremophiles. 

Although the search for novel extremozymes is a hot area of research, the secondary metabolites of these same microbes have attracted little attention. While scientists isolate and characterize new proteins that are stable in extremes of temperature, pH and salinity, others are applying the tools of molecular biology rather than classical culture techniques to study microbial communities. The two techniques give a. very different view of community diversity in part because certain microbes may act like weeds, quickly outgrowing all other, more fastidious members of the community in culture. Many microbes may... 

A number of smaller enzyme-producing companies focus on thermophilic micro-organisms (and other extremophiles) to identify and produce new types of thermostable enzymes Unitika, Pacific Enzymes, Genis, Diversa (formerly Recombinant BioCatalysis), and others. One extremozyme that has already found commercial application is the heat-stable DNA polymerase from Thermus aquaticus (Taq-polymerase) that gave rise to the polymerase chain reaction (PCR). Using PCR, nucleic acids or segments of DNA can by amplified in vitro without having to replace the enzyme after each amplification cycle when the DNA template is denatured by heat. A number of new hyperthermophilic enzymes with temperature optima between 75 and 118°C have been described in the past few years [81], such as... 

Eichler, J. 2001. Biolechnologieal uses of archaeal extremozymes. Biotechnol. Adv. 19, 261-278. 

Goldsmith, P., Amankwah, F., Gunjal, K., and Smith, J. 2003. Financial feasibility of producing value-added seafood from shrimp waste in Quebec. J. Aquat. Food Prod. TechnoL 12, 39-61. Gomes, J. and Steiner, W. 2004. The biocatalytic potential of extremophiles and extremozymes. Food TechnoL Biotechnol. 42, 223-235. 

---