Purification and Characterization of a Cysteine Protease Inhibitor from Chum Salmon(Oncorhynchus keta)Plasma

摘要

A cysteine protease inhibitor(CPI)in chum salmon(Oncorhynchus keta)plasma(CSP)was detected after performing inhibitory activity staining against papain under nonreducing condition.The CPI was purified from CSP by affinity chromatography with a yield and purification ratio of 0.94% and 30.36-fold,respectively.CSP CPI had a molecular mass of 70 kDa based on the results of SDS-PAGE and Sephacryl S-100 gel filtration.CSP CPI was a glycoprotein based on the periodic acid-Schiff(PAS)staining of the SDS-PAGE gel and classified as a kininogen.CSP CPI was stable in the pH range of 6.0-9.0 with maximal stability at pH 7.0.CSP CPI presented thermal stability at temperatures below 50°C and exhibited maximal activity at temperatures of 20-40°C.CSP CPI was determined to be a noncompetitive inhibitor against papain,with an inhibitor constant(K_i)of 105 nM.