Isolated from Tritirachium album. Proteinase K is a serine endopeptidase with a molecular weight of 28,000 that exhibits a broad spectrum of action. In addition to cleaving peptide bonds, it catalyzes peptide amide hydrolysis. Calcium ions do not affect the activity of the enzyme, but they do contribute to stability when present in concentrations of 1-5 µmoles. Proteinase K retains activity in the presence of sodium dodecyl sulphate (SDS) or urea (0.5-1% SDS and 1-4 M urea). Raising the reaction temperature from 37°C to 50°C-60°C can increase the enzyme's activity several fold. Proteinase K is able to digest native proteins, thereby inactivating enzymes such as DNase and RNase without recourse to a denaturation process.
Proteinase K is inactivated by diisopropyl fluorophosphate (DFP) or phenyl methane sulphonyl fluoride (PMSF). Chelating agents such as citrate and EDTA have no affect on the enzyme's activity.
Proteinase K is useful in the isolation of highly native, undamaged DNAs or RNAs, since most microbial or mammalian DNases and RNases are rapidly inactivated by the enzyme, particularly in the presence of 0.5-1% SDS.
|Storage:||Store at 4°C.|
|Activity:||lyophilized Proteinase K supplied at 8 U /mg (DMC) equivalent to 32 U/mg (Manson)|
|Unit definition:||1 DMC-unit catalyzes the hydrolysis of 1 mole Eq of di-methylcasein per min at 25°C, pH 7.0. 1 Manson unit produces 1mmole aminoacid after 1 min at 37.5°C, pH 2.0.|
|Quality control:||highly purified lyophilized powder, tested to ensure absence of DNase and RNase.|