Figure 4.

Effect of SPINK2 and α1‐antitrypsin on serine protease activity in sperm extracts. Twenty micrograms of proteins extracted from sperm were incubated with increasing amounts (0–800 nM) of purified SPINK2 (■) and α1‐antitrypsin (○) in a 50 mM Tris‐HCl buffer, pH 8.0 at 37°C for 20 min. The percentage of remaining sperm protease activity is indicated in y‐axis and inhibitor concentration (nM) is indicated in x‐axis