Abstract: Tomato fruits infected with Fusarium oxysporum produced proteins which exhibited proteolytic activity. The enzyme was partially purified by molecular exclusion and ion-exchange chromatography. Two components with molecular weight estimates of approximately 112, 000 and 63,100 were expressed. The enzyme exhibited maximum activity at pH 6.0 and 35°C. It possessed an apparent Km of approximately 4.3 mg mL-1 for casein. The enzyme was stimulated by the monovalent cations, Na+ and K+ and by the divalent cations; Mg++ and Ca++ but inhibited by ethylene diamine tetra acetic acid and mercuric chloride.