Homologous 3D model of human acrosin was built on the basis of the crystal coordinates of ram and boar acrosin, while the reliability of the model was assessed by Ramachandran plot and Profile-3D analysis. The active site of human acrosin was searched by Insight II/binding site analysis and important functional residues were located at the active site. To explore the binding mode of the 4-guanidinobenzoates with the active site of human acrosin, KF950 was docked into the active site and specific hydrogen-bonding interaction was found to play an important role in inhibitor recognition and orientation. These results provided a basis for the rational design of specific inhibitors to the target enzyme and the discovery of novel contraceptive agents with high potency.

Key words: human acrosin, homology modeling, active site, 4-guanidinozoic acid (4-methoxycarbonyl)- phenyl ester monomesylate, molecular docking