Proteinase K (Tritirachium album limber); Purity: A lyophilized powder. Chromatographically purified to remove DNase and RNase activity. Stable over a wide pH range : 4.0-12.5, optimal pH 7.5-8.0, using denatured hemoglobin as substrate. Although calcium ions do not affect the enzyme activity, they do protect Proteinase K against autolysis and increase thermal stability when present at a concentration of 1-5moles. It retains its activity in the presence of SDS or urea (0.5-1% SDS and 1-4M urea). Raising the temperature of the reaction from 37C to 50-60C can increase the activity several fold. Proteinase K is inactivated by diisopropyl fluorophosphate or phenyl methane sulphonyl fluoride. Chelating agents such as citrate and EDTA have no effect on the enzyme activity. Proteinase K can also be inactivated by heating above 65C for 15-20 min or by extraction with phenyl/chloroform., 100 mg