Zona Pellucida-Binding and Fucose-Binding of Boar Sperm Acrosin is Not Correlated with Proteolytic Activity

The major fucose-binding protein of 53 kDa was isolated from boar spermatozoa by mild detergent extraction and subsequent high-performance gel filtration and reversed-phase high-performance liquid chromatography. This protein has been identified as high-molecular-mass acrosin by N-terminal sequencing. Treatment of the isolated protein with diisopropyl fluorophosphate abolishes the enzymatic activity but not the zona pellucida- and fucose-binding properties. Mercaptolysis and S-pyridyl-ethylation of native two-chain acrosin followed by HPLC and SDS-PAGE revealed that the binding properties are located on the acrosin heavy chain.