Oocyte maturation involves the activation of various signal trans - duction pathways that converge to activate maturation - promoting factor ( mpf ) ; this is a key activity that catalyses entry into m - phase of meiosis i and meiosis ii 在爪蟾卵中有大量未被激活的cdc2 - cyclinb复合物，称为pre - mpf ， pre - mpf在tyr15位脱磷酸变成活性mpf ，起到这个作用的磷酸酶是cdc25 ， cdc25的活性通过磷酸化和细胞位置进行调控。
