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A novel extracellular protease with fibrinolytic activity from the culture supernatant of Cordyceps sinensis: purification and characterization

A novel serine protease with fibrinolytic activity named CSP was purified from the culture supernatant of the fungus Cordyceps sinensis, a kind of Chinese herbal medicine. Analysis of the purified enzyme by SDS‐PAGE indicated that CSP was a single polypeptide chain with an apparent molecular weight of 31 kDa, and N‐terminal sequencing revealed that the first ten amino acid residues of the enzyme were Ala‐Leu‐Ala‐Thr‐Gln‐His‐Gly‐Ala‐Pro‐Trp‐. When casein was used as a substrate, the proteolytic activity of CSP reached its maximum at pH 7.0 and 40 °C. The effect of chemical agents on the enzyme activity indicated that CSP is a serine protease with a free cysteine residue near the active site. It hydrolysed fibrinogen, fibrin and casein with a high efficiency, while hydrolysing bovine serum albumin (BSA) and human serum albumin (HSA) to a lesser extent. CSP was found to be a plasmin‐like protease, but not a plasminogen activator, and it preferentially cleaved the Aα chain of fibrinogen and the α‐chain of fibrin. Therefore, the extracellular protein CSP may represent a potential new therapeutic agent for the treatment of thrombosis. Copyright © 2007 John Wiley & Sons, Ltd.