# FAQ: What buffer should I use for Proteinase K?

Proteinase K is active in a wide range of buffers including all Restriction Enzyme NEBuffers, Q5 Reaction Buffer, OneTaq Standard Reaction Buffer, Standard Taq Reaction Buffer and RNAPol Reaction Buffer. Proteinase K is active with an optimal pH between 7.5 and 12.0 (Ebeling et al., 1974) and temperatures between 20 and 60°C (Bajorath et al., 1988). Activity is stimulated when up to 2% SDS or up to 4 M Urea are included in the reaction (Hilz et al., 1975). Calcium is important for thermostability of Proteinase K but it is not required for catalysis, therefore Proteinase K is also active in buffers containing chelating agents such as EDTA (Bajorath et al., 1988).