The heating of protein preparations of mesophilic organism (e.g.,
E. coli) producesthe obliteration of all soluble multimeric proteins from this organism. In this way, ifa multimeric enzyme from a thermophilic microorganism is expressed in thesemesophilic hosts, the only large protein remaining soluble in the preparation afterheating is the thermophilic enzyme. These large proteins may be then selectivelyadsorbed on lowly activated anionic exchangers, enabling their full purification in justthese two simple steps. This strategy has been applied to the purification of an
![](/images/gifchars/alpha.gif)
-galactosidase and a
![](/images/gifchars/beta2.gif)
-galactosidase from
Thermus sp. strain T2, both expressed in
E. coli, achieving the almost full purification of both enzymes in only these two simplesteps. This very simple strategy seems to be of general applicability to the purificationof any thermophilic multimeric enzyme expressed in a mesophilic host.