Thermophilic organisms, proteins

Some good hints to help answer this question have been obtained by studying thermophilic proteins which are in turn obtained from thermophilic organisms. The optimum growth temperature for thermophilic organisms is between 40° and 65°C (moderate thermophiles) and 70° and 105°C (extreme thermophiles). Their respective enzymes have catalytically indistinguishable reactivity and catalytic sites from those isolated from mesophilic organisms. 

Knowing that peptides and amines confer thermal stability on enzymes from certain thermophilic organisms (47-49) led some workers to examine protein stabilization by antibodies. It was found that the presence of specific polyclonal antibodies stabilize several enzymes (50, 51). In addition, not only did antibodies increjise the thermostability of a-amylase, glucoamylase, and subtilisin, but some stability toward acid denaturation, oxidizing agent, and organic solvent exposure was increased in specific cases (52, 53). 

Whereas heat precipitation is used only very rarely with proteins originating from mesophilic organisms, it is a very common step in the purification protocols of proteins from thermophilic organisms, which have been doned and expressed in E. coli. However, even in these cases, it is important that the incubation time is kept as short as possible to minimise deamidation of glutamine and asparagine residues. 

We end this chapter with two much simpler reactions - a couple of desymmetrisations - each special in their own way. The hrst is amazingly efficient, using a lipase/esterase from a thermophilic organism supplied as a recombinant protein by the Diversa corporation. The symmetrical Diels-Alder adduct 231 is rapidly and perfectly desymmetrised to the monoacid61 232 at 70 °C. 

The concept of using heat shock proteins as templates for nanoparticle assembly was further explored by Trent etal. through genetic manipulation of the 9 fi subunits of a heat shock protein isolated from the thermophillic organism of Sulfolobus shibatae This protein offered numerous benefits... 

Fig. 1. Hypothetical temperature profiles of the free energy of (a) mesophilic and (b-d) thermophilic proteins. AC is defined as the difference in the free energies between the native and denatured states. Tm and are the melting temperatures of the mesophilic and thermophilic variants, respectively. The minimum of the AC parabola for a given protein (i.e., maximum stability) is observed at a temperature that is much below the optimal temperature (Topt and T p,) of the respective mesophilic or thermophilic organism.

WedlerFC, Hoffman FM, Kenny R, Garfi J (1976) Maintenance of specificity, information and thermostability in thermophilic Bacillus sp. glutamine synthetase. In Zuber H (ed) Enzymes and proteins from thermophilic organisms. Birkhauser Verlag, Basel, p 187... 

The importance of the ionic bonds in the thermostabilization was emphasized by Perutz (1978). From differences in rate of denaturation in mesophilic and thermophilic molecules, Perutz (1978) has evaluated the extrastabilization energy to be no more than 2 kcal/mole in ferredoxin and 5-10 kcal/mole in glyceraldehyde-3-phosphate dehydrogenase. Proteins from thermophilic organisms offer a very good example, allowing one to... 

Stability of several enzymes like proteases from thermophilic micro-organisms can be increased in aqueous-organic biphasic systems. Owusu and Cowan [67] observed a strong positive correlation between bacterial growth temperature, the thermostability of free protein extracts, and enzyme stability in aqueous-organic biphasic systems (Table 1). Enzymes, like other cell components (membranes, DNA, (RNA ribosomes), are adapted to withstand the environmental conditions under which the organism demonstrates optimal growth. 

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