Purification and Characterization of Serum Serpin from Carp (Cyprinus carpio)

A serine proteinase inhibitor, termed serpin62, was purified to homogeneity from carp serum with an increase in specific inhibitory activity of 6.2-fold and a 3% recovery rate after separation from α₁-antitrypsin. Specific inhibitory activity of serpin62 against bovine pancreatic trypsin was less than half of the specific antitryptic activity of α₁-antitrypsin. Under both reducing and nonreducing conditions, serpin62 was estimated to have a molecular weight (62,000) apparently larger than that of α₁-antitrypsin (55,000). They both consist of single polypeptide chains, but serpin62 differs from serine proteinase inhibitors from muscles of carp and white croaker in molecular weight and structure. Antibody raised against serpin62 immunologically crossreacted with serpin62 and had no crossreactivity with fish serum α₁-antitrypsin and muscular analogues. The antibody was susceptible to both serpin62 and its derivatives, which were widely distributed in carp tissues. Serpin62 is most likely distinct from other fish serine proteinase inhibitors expressing antitryptic activity physicochemically and immunologically. Received June 4, 1998; accepted September 10, 1998.