Proteinase K is a stable serine protease with broad substrate
specificity. It degrades many proteins in the native state even in
the presence of detergents. Proteinase K was isolated from a fungus
able to grow on keratin and the enzyme can digest native keratin
(hair); hence its name "Proteinase K". Evidence from crystal and
molecular structure studies indicates the enzyme belongs to the
subtilisin family with an activesite catalytic triad (Asp39-His69-Ser224). The predominant site of cleavage is the peptide bond adjacent to
the carboxyl group of aliphatic and aromatic amino acids with
blocked alpha amino groups. It is commonly used for its broad
specificity. The mode and specificity of action has been studied.
Proteinase K is frequently used in molecular biology applications
to digest unwanted proteins, such as nucleases from DNA or RNA
preparations from microorganisms, cultured cells, and plants. The
enzyme is typically used at 50200 ug/ml in nucleic acid
preparations at pH 7.58.0 and 37℃. Incubation times vary from 30
minutes to 18 hours. Proteinase K is usually removed by subsequent
phenol extractions, although it can autodigest during long
Proteinase K has been used to remove endotoxins bound to cationic
proteins such as lysozyme and ribonuclease A. It has been used for
determination of enzyme localization on membranes, treatment of
paraffin embedded tissue sections to expose antigen binding sites
for antibody labeling, and remove nucleases for in situ
Research on prions in Transmissible Spongiform Encephalopathies
(TSE) and proposed diagnostic tests utilize Proteinase K digestion
of proteins from brain tissue samples. Protease footprinting by
Proteinase K digestion can reveal protein-protein surface
Proteinase K is active in 1% TritonTM X-100 and fully active in 0.5% (w/v) SDS. SDS and urea will
denature protein substrates resulting in increased digestion rates.
Proteinase K itself is denatured much more slowly by these agents.
Molecular mass: 28,930 Da (amino acid sequence); 28,500 Da
Extinction coefficient: E1% = 14.2 (280 nm, 10 mM NaCl and 5 mM
CaCl2, pH 8.0)
Activators: 15 mM Ca2+ is required for activation. When calcium is removed from the
enzyme (by addition of EDTA), 25% of the catalytic activity is
lost. However, if the EDTA-Ca2+ complex is removed from the enzyme solution by gel filtration, a
total of 80% of the enzyme activity is lost and only a small
activation will occur
upon addition of excess Ca2+ to the Ca2+-free enzyme.
InhibitorsProteinase K is inhibited by DIFP or PMSF (the latter
used at final concentration 5 mM). It is partly inactivated, but
not inhibited, by EDTA (see Activators). Proteinase K is not
inhibited by iodoacetic acid, the trypsin-specific inhibitor TLCK,
the chymotrypsin-specific inhibitor TPCK, and
One unit will hydrolyze urea-denatured hemoglobin to produce color
equivalent to 1.0 umole
(181ug) of tyrosine per minute at pH 7.5 at 37℃.
Appearance: White lyophilized powder
pH: 7.512.0 (urea-denatured hemoglobin as substrate), but most
often used in pH range 7.59.0.
Temperature: maximum activity at 37℃ (In the temperature range of
2060℃, a minimum of 80% of the activity observed at 37℃ is
Precautions and Disclaimer
This product is for R&D use only, not for drug, household, or
other uses. Please consult the Safety Data Sheet for information
regarding hazards and safe handling practices.
This product is soluble in water (12 mg/ml).
Shelf Life & Storage
This product is supplied as a lyophilized powder. Store the product
A Proteinase K solution remains active over a broad pH range
(4.012.5, optimal pH 8.0) and also over the temperature range of
2565℃ during use. At pH 8.0, solutions remain active for at least
12 months at 28℃. At pH 411.5, solutions containing Ca2+ (16 mM) are expected to remain active for several weeks. An 80%
ammonium sulfate suspension stored at 28℃ remains active for at
least 12 months.
1g/bag, 5g/bag, 10g/bag, or as request.