Catalyzes peptide amide hydrolysis

 • Broad spectrum of action

 • Cleaves peptide bonds

 • Active in SDS and urea

Proteinase K (EC 3.4.21.14. Isolated from Tritirachium album) is a serine endopeptidase with a molecular weight of 28000. It exhibits a broad spectrum of action, in addition to cleavage of peptide bonds, it is able to catalyze 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. 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 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 fluorophosphates (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.