Presence of follipsin complexed with alpha 2-macroglobulin in porcine ovarian follicular fluid.

Using the follicular fluid of porcine ovaries as a source, a high-molecular-weight protein having enzyme activity toward t-butyloxycarbonyl-Gln-Arg-Arg-4-methylcoumaryl-7-amide was purified to an apparent homogeneity. Its molecular weight was estimated to be approximately 720,000. The protein was immunoprecipitated with antihuman alpha 2-macroglobulin antibody and was visualized in Western blot analysis using the same antibody. Using Western blot analysis, an 85 kDa polypeptide, which was recognized by antiporcine follipsin antibodies, was detected in this high-molecular-weight protein. When tested for substrates and inhibitors with low molecular weight, the protein showed substrate specificity and an inhibitor profile similar to those of follipsin. On the basis of these results, it was concluded that the protein is a complex of follipsin with alpha 2-macroglobulin. The complexed enzyme activated a single-chain precursor tissue-type plasminogen activator at a drastically reduced rate compared with free follipsin. The present results suggest that intrafollicular follipsin activity is regulated by the proteinase inhibitor alpha 2-macroglobulin.