Enzymatic Reaction (image will open in a new window)
Proteinase K (PROK) is a serine endopeptidase with a broad spectrum of action, isolated from the filtrate of the fungus Tritirachium album limber.
Characteristics of Proteinase K from Tritirachium album limber:
Molecular weight: 28,900 daltons.
pH Optimum: 7.5 - 12, using denatured hemoglobin as substrate.
Stability: Although calcium ions do not affect the enzyme activity, they do contribute to its stability when present at a concentration of 1 - 5 μmoles. An interesting characteristic of proteinase K is that it retains its activity in the presence of sodium dodecyl sulphate (SDS) or urea. (0.5 - 1% SDS and 1 - 4 M urea). Raising the temperature of the reaction from 37°C to 50°C - 60°C can increase the activity several folds. A special feature of proteinase K is its ability to digest native proteins, thereby inactivating enzymes such as DNase and RNase without recourse to a denaturation process.
Specificity: In addition to cleavage of peptide bonds, it is able to catalyze peptide amide hydrolysis. 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 activity.
Application: Proteinase K is very 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: PROK: Store at 2 - 8°C; PROKS: Store @ -20°C
Worthington PROK is supplied as a highly purified lyophilized powder. Code PROKS is a 20mg/ml solution containing 50% glycerol. Both are tested to be free of DNase and RNase.