Proteinase K (250 mg)

A lyophilized, highly purified powder from QIAGEN, this recombinant Proteinase K is a subtilisin-related serine protease from Parengyodontium album (Tritirachium album), expressed in Komagataella phaffii (Pichia pastoris). It is a 28.9 kDa broad-spectrum endopeptidase for highly effective protein digestion across many laboratory applications, and is free of DNase and RNase activity.

The enzyme is typically used at 50–200 µg/mL in nucleic acid preparations at pH 7.5–8.5 and 37–55°C, with incubation times from 30 minutes to 18 hours. The working pH range is 4.0–12.0 with optimum activity at pH 7.5–8.5, and the working temperature range is 20–65°C with optimum activity at 50–56°C. Activity is stimulated by 0.2–1% SDS or 1–4 M urea, while Ca2+ (1–6 mM) protects the enzyme against autolysis and increases its thermal stability. The enzyme is not inactivated by chelating agents (e.g., EDTA), chaotropic salts, detergents, metal ions, thiol reagents, or trypsin-specific inhibitors, but can be inactivated by heating above 65°C or by using inhibitors such as PMSF or DIFP.

Typical applications include inactivation of RNases and DNases during isolation of DNA or RNA from tissues and cell lines, removal of protein impurities, and improving cloning efficiency of PCR products. The lyophilized powder should be stored at –20°C, where it maintains activity of ≥30 U/mg and specific activity of ≥40 U/mg for at least 24 months when kept in the original, unopened container.