Application

Useful for the proteolytic inactivation of nucleases during the isolation of DNA and RNA.Removes endotoxins that bind to cationic proteins such as lysozyme and ribonuclease A.Reported useful for the isolation of hepatic, yeast, and mung bean mitochondriaDetermination of enzyme localization on membranesTreatment of paraffin embedded tissue sections to expose antigen binding sites for antibody labeling.Digestion of proteins from brain tissue samples for prions in Transmissible Spongiform Encephalopathies (TSE) research.

Protease footprinting by Proteinase K digestion can reveal protein-protein surface interactions. The enzyme from Sigma has been used in the pre-hybridization step of chicken embryos. It has also been used for the enrichment of PrPSc, a prion protein that is present in sheep, hamster and mouse scrapie samples.

Proteinase K is useful for the proteolytic inactivation of nucleases during the isolation of DNA and RNA.It is used for the removal of endotoxins bound to cationic proteins such as lysozyme and ribonuclease A.It is useful for the isolation of hepatic, yeast, and mung bean mitochondria and is used to determine enzyme localization on membranesIt is used for the treatment of paraffin embedded tissue sections to expose antigen binding sites for antibody labeling and for digestion of proteins from brain tissue samples for prions in Transmissible Spongiform Encephalopathies (TSE) research. Product SAE0009 is provided as a lyophilized powder. Product SAE0009 has been used to break down human lens protein¹.

Biochem/physiol Actions

Proteinase K has a broad specificity and degrades many proteins even in the native state. It mainly cleaves the peptide bond adjacent to the carboxyl group of aliphatic and aromatic amino acids with blocked a-amino groups.The optimum pH is between 7.5-9.0 and the isoelectric point is 8.9 Ca²⁺ (1-5 mM) is required for activation. Proteinase K is inhibited by diisopropyl fluorophosphate (DFIP), and phenylmethanesulfonyl fluoride (PMSF).

Proteinase 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 is stable in a broad range of environments: pH, buffer salts, detergents (SDS), and temperature. 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.

General description

Proteinase K (PK) from fungi, Tritirachium album encodes a 40 kDa protein. The N-terminal propeptide region shows homology with bacterial subtilisin. PK crystallizes even under microgravity conditions on the space shuttle mission. PK is an effective protein system for studying protein engineering process.

Unit 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).