Expression and purification of pseudomonas aeruginosa keratinase in Bacillus subtilis DB104 expression system

The DNA encoding Pseudomonas aeruginosa keratinase was ligated into pRPA expression vector and transformed into Bacillus subtilis DB104. Recombinant keratinase (rK), secreted by B. subtilis after 72 h of incubation, was purified to electrophoretical homogeneity by nickel affinity chromatography and found to have a molecular mass of 33 kDa. The rK had an optimal pH and temperature at 8.0 and 60 degrees C, respectively, and was stable at pH 6.0-9.0 and 10-50 degrees C. It was strongly inhibited by Cu(2+), Fe(2+), Hg(2+), Fe(3+), ethylene glycol tetraacetic acid, and ethylene diamine tetraacetic acid but activated by Ca(2+), Mg(2+), Zn(2+), dithiothreitol, glutathione, and beta-mercaptoethanol. According to substrate specificity, the rK was considered to be a metalloprotease.