Interactions of boar acrosin with detergents.

The activity of boar acrosin was found to be stimulated up to 260% by non-ionic detergents if present in concentrations above their critical micelle concentration. In addition, the stability of acrosin was remarkably enhanced in the presence of 0.1% (w/v) detergents. Triton X-100 was found to reduce the affinity of acrosin to the synthetic inhibitor 6-amidino-2(4'-methoxyphenyl)indole by the factor 2.9 when Ki values were measured in buffer solutions in the presence (0.1%, w/v) and absence of Triton X-100. Phospholipids did nearly completely abolish the acrosin activity, this effect being reversibly by addition of 0.1% (w/v) Triton X-100. These results are interpreted in terms of hydrophobic binding sites exposed on the surface of the acrosin molecule. Hence, for the first time data are presented characterizing acrosin as a membrane-associated protein.