Purification and biochemical characterization of a novel protease from Penicillium digitatum - Use in bioactive peptides production

This work reports the production of a novel serine protease enzyme (P. dig-protease) from the fungus Penicillium digitatum. The protease was purified from the culture supernatant to homogeneity using ammonium sulfate precipitation, Sephadex G-150 gel filtration and carboxymethyl-sepharose ion exchange chromatography with a 13-fold increase in specific activity. The apparent molecular weight of P. dig-protease was estimated to be 120 kDa by native high performance liquid chromatography (HPLC), sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed a single polypeptide at about 30 kDa that indicates a tetrameric protein. The proteolytic activity was inhibited by phenylmethylsulfonyl fluoride suggesting a serine-protease enzyme. P. dig-protease stability was investigated over broad range of pH, temperature, salt concentrations, surfactants and metal ions. The purified P. dig-protease was used for the production of bioactive peptides. Red scorpionfish (Scorpaena notata) muscle was hydrolyzed with P. dig-protease in order to obtain peptides with biological activities. Interestingly, the hydrolysate revealed the presence of antioxidant and angiotensin-I converting enzyme inhibitor peptides.