A lipase from Rhizopus sp.ZM-10 was purified to homogeneity using ammonium sulfate precipitation,dialysis,DEAE-Sepharose Fast Flow anion exchange chromatography and Sephadex G-100 gel filtration chromatography.This purification protocol resulted in a 15.3-fold purification of lipase with 22.2% final yield,and the relative molecular weight of the enzyme was determined to be approximately 42 ku using SDS-PAGE.Six modifiers(NBS,EDC,DEPC,CH-T,PMSF,DTNB) were used to react with Rhizopus sp.ZM-10 lipase.The result indicated that aspartate(glutamate),histidine,serine and tryptophan residues were essential groups for the catalytic activity;aspartate(glutamate),histidine and serine residue were in the substrate binding site,and tryptophan residue was important in maintaining the enzyme activity,but not in the substrate binding site of the enzyme.