Boar Acrosin. Isolation of Two Active Forms from Boar Ejaculated Sperm

Abstract

A simple method avoiding the use of nonionogenic detergent was developed for the isolation of 2 forms of boar acrosin from ejaculated sperm. Each of the 2 forms was electrophoretically homogeneous and showed 1 N-terminal sequence only: Val-Val. The 2 acrosin forms isolated differ in molecular mass and amino acid composition. .alpha.-Acrosin, the form showing a higher molecular mass (MW .apprx. 50,000), is stable in acid media. When exposed to pH > 4, it is converted into .beta.-acrosin (MW .apprx. 35,000) by autodigestion. The isolation of the .alpha.-form was therefore carried out below pH 4 to eliminate autodigestion to the .beta.-form. The .beta.-form is stable for a certain period at neutral pH, especially if stabilized by Ca2+ ions. The autodigestion of .alpha.-acrosin to .beta.-acrosin probably results in the liberation of the C-terminal portion of the molecule of the .alpha.-form; this portion is composed of roughly 85 residues and is rich in proline.