Proteinase K (PROK) is a serine protease with broad specificity towards aliphatic, aromatic and other hydrophobic amino acids. PROK has a molecular weight of 27,000 daltons and is Ca2+ dependent. It is not inactivated by metal ion chelating agents such as EDTA, sulfhydryl reagents, PCMB, TLCK, or TPCK. It also retains activity in 0.5% SDS. It can be inhibited by PMSF or DFP.