Purification and characterization of an aspartic protease from potato leaves

A protease was isolated from potato (Solanum taberosum L. cv, Pampeana) lea ves 48 h after detaching, when aspartic protease (AP) activity is markedly increased, Purification was performed by ammonium sulfate precipitation, io n exchange chromatography and affinity chromatography. A size of 40 kDa was estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis; it is monomeric and its properties are consistent with those of aspartic prot einases (EC 3.4.23): it has a pH optimum of 3 and it is inhibited by pepsta tin. Like other plant APs, leaf AP appears to be glycosylated with a comple x-type N-glycan. The enzyme has properties different from those of a tuber AP previously described, indicating that they may have different physiologi cal roles.