Proteinase K

Infectious proteins (prions) are, ironically, defined by their resistance to proteolytic digestion. A defining characteristic of the transmissible isoform of the prion protein (PrP(Sc)) is its partial resistance to proteinase K (PK) digestion. Diagnosis of prion disease typically relies upon immunodetection of PK-digested PrP(Sc) by Western blot, ELISA or immunohistochemical detection. PK digestion has also been used to detect differences in prion strains. Thus, PK has been a crucial tool to detect and, thereby, control the spread of prions. PK has also been used as a tool to probe the structure of PrP(Sc). Mass spectrometry and antibodies have been used to identify PK cleavage sites in PrP(Sc). These results have been used to identify the more accessible, flexible stretches connecting the β-strand components in PrP(Sc). These data, combined with physical constraints imposed by spectroscopic results, were used to propose a qualitative model for the structure of PrP(Sc). Assuming that PrP(Sc) is a four rung β-solenoid, we have threaded the PrP sequence to satisfy the PK proteolysis data and other experimental constraints.

In this study, enzyme-inorganic hybrid nanoflowers were synthesized using proteinase K and Cu2+ions. The synthesized proteinase K-Cu2+hybrid nanoflowers (P-hNFs) were characterized by their morphology and chemical point of view by using different techniques such as SEM, FTIR, EDX, and XRD. The proteolytic activities and some important characteristics such as optimum pH and temperature of the P-hNFs were also evaluated by comparison with free proteinase K. Optimum pH values of free proteinase K and P-hNFs were determined as pH 10 and pH 11, respectively. Optimum temperatures recorded for both free proteinase K (at pH 10) and P-hNFs (at pH 11) were 40 °C. In our study, for the first time, using some commercial detergents and surfactants, the utility of the P-hNFs as a detergent additive was also systematically evaluated. In these studies, the P-hNFs exhibited better activity than free proteinase K in the presence of all surfactants (CHAPS, DOC, SDS, Triton X-100 and Tergitol) except for Tween 80. Importantly, the P-hNFs was more stable and compatible with all tested solid laundry detergents. The findings demonstrated that the P-hNFs could potentially be used as an additive in detergent formulations.

This study investigates the interfacial behavior of the proteinase K enzyme at air-water interface. Adsorption of enzyme on the surface was induced using saline subphase. The surface packing and stability of the enzyme was investigated using of surface pressure-area (π-A) and surface potential-area (ΔV-A) isotherms. Proteinase K enzyme forms film at air-aqueous interface and demonstrates good stability as shown through compression-decompression cycle experiments. To characterize the surface assembly morphology of the interfacial enzymes UV-vis and fluorescence spectroscopic techniques were used. The data revealed that the enzyme Langmuir monolayer has good homogeneity with no evidence of aggregates during compression. The secondary structure of the enzyme at interface was determined to be α-helix using p-polarized infrared-reflection absorption spectroscopy. This was confirmed through Circular dichroism spectra of the enzyme Langmuir-Blodgett (LB) film which showed that the major conformation present were α-helices.