Stability of protease Q against autolysis and in sodium dodecyl sulfate and urea solutions

Protease Q, a recently discovered subtilisin-like protease, exhibited unusual stability in 10% sodium dodecyl sulfate (SDS) and 8 M urea solutions. In 2% SDS it exhibited higher activity than the control, and in 10% SDS it retained 50% of its original activity when azocoll was used as substrate. Kinetic studies showed that the decrease in the activity of protease Q in SDS solutions followed a first order kinetics with a half-life of 446, 278, 78, and 24 h in 1%, 2%, 5%, and 10% SDS, respectively, at 25 degrees C. Protease Q was also stable against autolysis. In 20 mM Tris-HCl buffer (pH 8.3) containing 1.0 mM CaCl2, protease Q had a half life of 2822 h and 725 h at room temperature and at 37 degrees C, respectively. The enzyme was able to completely hydrolyze beta-lactoglobulin, beta-casein, and keratin in 8-10 M urea.