Proteinase K (1 g)

QIAGEN supplies this lyophilized powder preparation of a broad-spectrum, subtilisin-related serine protease originally derived from the fungus Parengyodontium album (Tritirachium album). The recombinant 28.9 kDa enzyme is expressed in Komagataella phaffii (Pichia pastoris) and is extensively purified for high solubility, specific activity and low residual DNA content.

The enzyme cleaves peptide bonds adjacent to the carboxyl group of aliphatic, aromatic and other hydrophobic amino acids. It is active across a wide range of temperatures and pH values, with high activity between 50–65°C across pH 7.5–12.0, and remains stable in the presence of denaturing reagents such as SDS and urea and chelating agents such as EDTA. Soluble calcium is not essential for its activity, so EDTA does not inhibit the enzyme. Its high specific activity enables efficient digestion of proteins — including DNases and RNases — during nucleic acid preparation without compromising DNA or RNA integrity.

For this powder format, QIAGEN specifies activity of ≥30 U/mg lyophilizate and ≥40 U/mg protein, with DNA content ≤10 pg/mg. Storage is at –20°C with ambient shipping, and the format is highlighted for high stability and reproducibility. The enzyme is routinely used for the isolation of genomic, plasmid and high molecular weight DNA and RNA, as well as for the digestion of structural proteins and chromatin. According to QIAGEN, Proteinase K cannot be completely heat-inactivated; residual activity remains even after incubation at 95°C for 10 minutes.