Proteinase K, Molecular Biology Grade, >30 units/mg protein

Proteinase K, Molecular Biology Grade, >30 units/mg protein

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SKU: E008-1

Proteinase K (Endopeptidase K) is a stable and highly reactive serine protease. Evidence from crystal and molecular structure studies indicates the enzyme belongs to the subtilisin family with an active-site catalytic triad (Asp39-His69-Ser224). It remains stable and active in the presence of chemicals that usually denature proteins, such as SDS and urea, chelating agents such as EDTA, sulfhydryl reagents, as well as trypsin or chymotrypsin inhibitors. In the presence of 0.1-0.5% SDS, proteinase K retains activity and will digest a variety of proteins and nucleases in DNA preparations without compromising the integrity of the isolated DNA. The optimum pH is between 7.5-9.0 and the isoelectric point is 8.9.  Ca2+ (1-5 mM) is required for activation. 

Activity Definition: 

One unit will hydrolyze urea-denatured hemoglobin to produce color equivalent to 1.0 μmole of tyrosine per min at pH 7.5 at 37 °C (color by Folin-Ciocalteu reagent).


Proteinase K is commonly used in molecular biology to digest protein and remove contamination from preparations of nucleic acid. Addition of Proteinase K to nucleic acid preparations rapidly inactivates nucleases that might otherwise degrade the DNA or RNA during purification.

Recommend Usage

Prepare recombinant Proteinase K with 50 mM Tris-HCl, 2 mM Calcium acetate.The optimum pH is 8.0.


  • Origin: Recombinant Proteinase K from Tritirachium album
  • Purity: 99%, DNAses and RNAses not detected
  • Activity: >30 units/mg protein
  • Appearance: Lyophilized white powder
  • MW: 28.9 kDa
  • CAS Number: 39450-01-6
  • EC:
Storage: −20°C