Proteases from Mucor had a good application prospect in the production of soy-polypeptides for their high hydrolysis efficiency to soy protein and debittering effect to hydrolysate.To explore these proteases,this study used ammonium sulfate precipitation,ion exchange chromatography,hydrophobic chromatography and gel filtration chromatography,and investigated the properties of one aminopeptidase purified from the fermented wheat bran by Actinomucor elegans AS3.2778.The purified aminopeptidase was a particular prolyl-aminopeptidase,which had a very high hydrolysis activity to N-terminal proline of peptides.It had the maximum activity at pH6.5 40~45℃,was stable in the pH range of 5.0~8.0 at <30℃,and could be inhibited by the serine protease inhibitor,PMSF,indicated that it may belong to the serine protease family.The effect of debittering for bitter peptides among SPI hydrolysate with Alcalase was clearly found by proly-aminopeptidase treatment for 3 h.