Thermo Scientific Proteinase K is a broad-range endolytic protease widely used for digestion of proteins in nucleic acid preparations. It degrades proteins even in the presence of detergents. Proteinase K cleaves peptide bonds at the carboxylic sides of aliphatic, aromatic, or hydrophobic amino acids. The Proteinase K is classified as a serine protease. The smallest peptide to be hydrolyzed by this enzyme is a tetrapeptide.