Proteinase K Lyophilized Powder, ≥ 30 U/mg, Recombinant (Yeast). Proteinase K, a broad-spectrum serine protease, is first extracted and purified from Engyodontium album. It is named Proteinase K because it can degrade Keratin. The crystallization and molecular structure of Proteinase K indicates it belongs to subtilisin family; whose active site has a characteristic catalytic triple amino acid Asp39-His69-Ser224. Proteinase K has no significant substrate specificity and main cleavage site is the peptide bond at the carboxyl end of the hydrophobic amino acid such as aliphatic or aromatic. Recombinant Proteinase K is derived from yeast based on the optimized gene of Engyodontium album by site-directed mutation. It is purified by chromatography process and with calcium and glycerin as protective agents. Extremely effective on native proteins and can be used to rapidly inactivate endogenous nucleases such as RNases and DNases. This property makes Proteinase K particularly suitable for the isolation of native RNA and DNA from tissues or cell lines.