Purification and characterization of a cathepsin inhibitor from catfish (Pangasius sp.) of Indonesian water
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Cathepsin inhibitor has been purified to homogeneity from catfish muscle (Pangasius sp.). The purification was carried out through ammonium sulphate precipitation, followed by ion exchange chromatography using DEAE-Sephadex A-75, followed by gel filtration on Sephadex G-100. Throughout the purification procedure, cathepsin inhibitory activity was determined against hemoglobin. A single band of molecular weight 16.65 kDa was obtained after the Sephadex G-100 filtration and revealed inhibitory activity against cathepsin as estimated by SDS-PAGE. The purified inhibitor possessed a specific activity of 16.9-fold higher than the initial activity with a 1.85 % yield. The optimum pH of the inhibitor was eight at 40°C. The inhibitor was stable at 10-50°C and at pH 7-9. Ions Mn2+ increased the inhibitory activity, while Ca2+ and Co2+ were slightly repressed. The enzyme inhibitor extracted from this study had similar properties to available commercial inhibitors.