Purification of Halophilic Enzymes

Halophilic enzymes are very unstable in low salt concentrations. Because some of the important fractionation methods in protein chemistry, such as electrophoresis or ion-exchange chromatography, cannot be applied at high salt concentrations, the available fractionation methods are rather limited. This basic difficulty is the main reason why the number of halophilic enzymes studied in pure form is very small. 

The existing purification procedures fall into two groups the non-halophilic approach and the halophilic approach. In the first, at certain stages in the purification procedure, the salt concentration is reduced and techniques that are suitable to low salt concentrations are applied. Inactivation in these conditions can be overcome partially either by protecting the native enzyme with its substrate or cofactors 

According to the halophilic approach, all the purification steps are performed in high salt concentrations. The advantage of this approach is the high level of recovery achieved in each step. This ap- 

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A very interesting application of affinity chromatography to the purification of halophilic enzymes was reported by Sundquist and Fahey (1988). These authors have purified the enzymes bis-y-glu-tamylcysteine reductase and dihydrolipoamide dehydrogenase from H. halohium using immobilized metal ion affinity chromatography in high-salt buffers. 

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