Purification of a sperm motility stimulator from porcine follicular fluid

1. We purified a glycoprotein possessing a potent ability to stimulate porcine sperm motility, from porcine ovarian follicular fluid. 2. The protein, of molecular weight 52,000, has an N-terminal sequence similar to that of antithrombin III, indicating that it is identical to or highly homologous to antithrombin III. 3. Thus it is proposed that antithrombin III or its homologue is involved in the mammalian fertilization process.