Occurrence of a latent serine protease in the follicular fluid of porcine ovary.

Porcine ovary follicular fluid contains a latent form of a protease which is activatable with trypsin. The active enzyme hydrolyzed peptide 4-methylcoumaryl-7-amide (MCA) substrates with a preference for the Arg-MCA bond. The enzyme was strongly inhibited by diisopropylfluorophosphate, aprotinin, leupeptin and antipain, but not by soybean trypsin inhibitor. The apparent molecular weight of the enzyme was approximately 630,000 as estimated by gel filtration. No significant difference in molecular size was seen between the inactive precursor and trypsin-activated enzyme. The results suggest that the present enzyme is a novel type of serine protease.