Enhancement of keratinolytic activity of a thermophilic subtilase by improving its autolysis resistance and thermostability under reducing conditions.

WF146 protease, a thermophilic subtilase from thermophile Bacillus sp. WF146, suffers excessive autolysis in the presence of reducing agents. In this report, two autolytic sites of WF146 protease were modified by site-directed mutagenesis. The introduction of prolines into the autolytic sites increased the autolysis resistance of the enzyme under reducing conditions. The double mutant N63P/A66P displayed a 2.8-fold longer half-life at 80 degrees C and higher hydrolytic activities than wild-type enzyme toward soluble (casein) and insoluble (keratin azure) substrates at high temperatures. In the presence of reducing agents, N63P/A66P was able to degrade feather at 80 degrees C ( approximately 3 h), with hydrolysis efficiency comparable to that of proteinase K at 50 degrees C ( approximately 24 h). Meanwhile, the mutant N63P/A66P had the ability to hydrolyze PrP(Sc)-like prion protein at high temperatures. In virtue of these properties, N63P/A66P is of great interest to be used in recycling of keratinous wastes, such as feather, and disinfection of medical apparatus. In addition, our study may provide useful information needed to explore keratinolytic potential of thermophilic subtilases, even if they are produced by non-keratinolytic microorganisms.