Proteinase K 39450-01-6, supplied under product code PK-PG-39450-01-6, is a subtilisin-type serine endoprotease obtained from Engyodontium album (formerly Tritirachium album). The native fungal enzyme is manufactured by submerged fermentation and purified through chromatographic steps to produce a white to off-white lyophilized powder. The pharmaceutical-grade API is designated for formulation into tablets, capsules, granules, and injectable preparations for oral and parenteral administration. Reported molecular mass is approximately 28.9 kDa, and the molecule contains two calcium-binding sites that contribute to thermal stability. In aqueous solution, activity is retained over pH 7.5–12, with an optimum near 55 °C. Unlike trypsin, Proteinase K remains active in 0.5% sodium dodecyl sulfate, 1% Triton X-100, and 1% Tween 20. The CAS registry number 39450-01-6 identifies the native protease preparation rather than a recombinant variant.

What Specifications Govern Proteinase K 39450-01-6 for Sterile and Non-Sterile Dosage Forms?

For each batch, the release specification includes activity, purity, and safety attributes that vary with intended route of administration. Injectable grade material requires bacterial endotoxin control below 0.1 EU/mg and compliance with USP <85>; oral grade material may be released with a higher endotoxin limit if supported by toxicity data. Specific activity is determined by casein hydrolysis at 37 °C and pH 7.5, with a typical acceptance criterion of not less than 30 U/mg. DNase and RNase activities are evaluated by incubation with DNA or RNA substrate followed by agarose gel electrophoresis; no substrate degradation should be observed. Residual moisture is controlled to ≤ 5.0% by USP <731>, and elemental impurities are determined by ICP-MS according to ICH Q3D. The product is not subject to a harmonized pharmacopoeial monograph for Proteinase K; therefore specifications are supplier-defined and aligned to ICH Q6B for biological drug substances. Table 1 summarizes the representative release profile for oral and injectable applications.

Process-related impurities in pharmaceutical-grade Proteinase K include residual host cell proteins, residual nucleic acids, and media components. The batch release program therefore combines orthogonal methods: SDS-PAGE for purity, ELISA for host cell protein, qPCR for residual DNA, and ICP-MS for elemental impurities. Purity by SDS-PAGE is typically specified as not less than 95%, with no single impurity band exceeding 5%. High-molecular-mass aggregates are monitored by size-exclusion chromatography and limited to ≤ 5.0% for injectable applications to reduce the risk of immunogenicity. Peptide mapping may be used to confirm enzyme identity against a reference standard of the native protease. These methods follow ICH Q6B and applicable USP general chapters for biological products.

Dry granulation is preferred over aqueous wet granulation for tablet and capsule formulations containing this protease because the enzyme undergoes irreversible thermal denaturation above 65 °C and loses activity at pH below 4.0 during prolonged exposure. Roller compaction on a laboratory-scale compactor with roll pressure 30–50 kN and gap 1.0–2.0 mm produces granules with bulk density 0.45–0.65 g/mL suitable for capsule filling or tablet compression. Air-jet milling of the lyophilized API at temperature ≤ 35 °C is used to reduce particle size to D90 ≤ 150 µm by laser diffraction, improving content uniformity in low-dose strengths. Blending in a twin-shell V-blender at 15–25 rpm for 10–15 min is specified; high-shear impellers above 500 rpm can induce local heating and protein aggregation. Tablet compression on an instrumented single-punch press with 8 mm round B-tooling is typically adjusted to 6–10 kN compression force to achieve hardness 60–80 N and friability ≤ 1.0% per USP <1216>. Capsule filling on a dosator or tamping-pin encapsulation line requires relative humidity below 40% RH to prevent powder sticking and fill-weight drift. For granules intended for suspension or sachet packaging, ambient relative humidity above 60% requires pre-drying of excipients and nitrogen purging of the granulation vessel to maintain moisture below 3.0%.

After oral administration, the enzyme is subject to gastric acid instability; immediate-release tablets and capsules are therefore unlikely to deliver intact protease to the small intestine without protection. Enteric coating with methacrylic acid–ethyl acrylate copolymer or hydroxypropyl methylcellulose acetate succinate is evaluated by two-stage dissolution testing: 2 h in 0.1 N hydrochloric acid at 37 °C, followed by pH 6.8 phosphate buffer. Published data for this specific enzyme in oral solid dosage forms is limited; acid-labile behavior must be confirmed by activity assay after simulated gastric fluid exposure. Alternatively, granules may be filled into hard-gelatin capsules with buffering excipients such as sodium bicarbonate or tromethamine to raise local pH. Diluent selection should avoid reducing sugars such as lactose monohydrate when storage exceeds 25 °C, because glycation of lysine residues can decrease specific activity. Mannitol and microcrystalline cellulose are preferred for direct compression and roller compaction due to low moisture and non-reducing behavior.

When Proteinase K Replaces Trypsin or Papain in Oral and Injectable Formulations

Because the enzyme retains proteolytic activity in 0.5% SDS and 1% nonionic surfactants, it is differentiated from trypsin, which undergoes rapid denaturation under the same conditions. Unlike papain and bromelain, Proteinase K does not require activation by L-cysteine or 2-mercaptoethanol; this removes thiol-related excipient incompatibilities in tablet and capsule matrices. The functional pH range of 7.5–12 is broader than that of trypsin (7.0–9.0) and papain (6.0–7.0), while pepsin is restricted to acidic conditions (1.5–3.5). Proteinase K is irreversibly inhibited by phenylmethanesulfonyl fluoride and diisopropyl fluorophosphate; therefore manufacturing equipment cleaning validation must demonstrate removal of these inhibitors if they are used in the same facility. Table 2 compares the relevant catalytic and stability properties with other proteases used in pharmaceutical formulation.

Aseptic processing rather than terminal sterilization is the required manufacturing route for injectable Proteinase K because moist-heat treatment at 121 °C causes irreversible aggregation and activity loss. The lyophilized API is dissolved at 2–10 mg/mL in a buffered vehicle at pH 6.0–7.5, typically 10–50 mM Tris-HCl or HEPES, and filtered through a 0.22 µm PVDF or PES membrane. Calcium chloride at 1–5 mM may be added to stabilize the calcium-binding sites, but phosphate buffers above 50 mM should be avoided because precipitation with calcium ions can reduce filter throughput and final product clarity. Lyophilization cycles for injectable dosage forms typically include freezing at -40 °C, primary drying at -20 °C to -10 °C for 24–48 h, and secondary drying at 25 °C for 8–12 h. Mannitol or trehalose at 4–6% w/v is used as cryoprotectant and bulking agent. Endotoxin in finished filled containers is verified per USP <85>, and container closure integrity is tested per USP <1207>. Proteinase K degrades gelatin, albumin, and casein; these proteinaceous excipients are incompatible in liquid formulations unless separated by lyophilization or replaced with non-degradable alternatives. Published data for this specific configuration is limited, so filter compatibility and hold times require process qualification runs on the actual aseptic filling line.

Enzyme activity in finished dosage forms is assayed by casein hydrolysis, and assay variability arises from sample preparation temperature and pH. Mechanical stress during capsule filling or tablet compression can reduce activity relative to the input API; therefore batch records should include in-process activity testing after granulation and after compression. The product is incompatible with strong oxidizing agents such as hydrogen peroxide and hypochlorite-based sanitizers; equipment cleaning should use alkaline detergents followed by rinses verified by total organic carbon or UV absorbance. Long-term storage of the bulk API is specified at -20 °C ± 5 °C with desiccant under nitrogen, and repeated freeze-thaw cycles are to be avoided. At 2–8 °C, opened containers should be used within 30 days unless stability data support a longer hold time.

Pharmaceutical-grade Proteinase K differs from molecular biology–grade reagent by controlled endotoxin, bioburden, residual solvents, and supply-chain documentation suitable for cGMP manufacturing under 21 CFR 210 and 211. Reagent-grade preparations may carry higher endotoxin loads and are not released with full ICH Q6B documentation; they are therefore not suitable as API for injection or oral drug product. The cGMP grade is supplied with certificate of analysis, origin statement, and stability data generated per ICH Q1A(R2).