A novel endopeptidase, IBSP82, has been purified from storage roots of sweet potato (Ipomoea batatas [L.] Lam) to electrophoretic homogeneity by four purification steps: ammonium sulfate precipitation, Superdex® 75 FPLC GFC, Superdex® 200 FPLC GFC and Tricine–sodium dodecyl sulfate–polyacrylamide (Tricine–SDS–PAGE) gel cutting. Its Mr was estimated to be 82 kDa by Tricine–SDS–PAGE. The enzyme activity of IBSP82 was strongly inhibited by 2 mM PMSF, but not at all by 2 mM iodoacetic acid, 5 mM EDTA or 20 uM pepstatin A. These results indicated that it was a serine type protease. The preferential cleavage sites for this protease were found to be hydrophobic and aromatic amino acid residues at the P1 sites. It was also found that this protease was able to cleave denatured sweet potato β-amylase but not denatured sweet potato trypsin inhibitors. The native sweet potato trypsin inhibitors neither inhibit IBSP82’s activity nor serve as its substrate. [Copyright &y& Elsevier]