In this study, we could detect cathepsin B-like, i.e., BANA-hydrolysing, enzymeactivity in the cytosolic fraction of mouse epidermal lysate. The optimum pH and the optimum temperature of this enzyme activity were pH 6.0 and 37℃, respectively. The BANA hydrolysis occured dose dependently to the protein amount of the cytosolic
fraction and, lupeptin, which is a specific inhibitor to cathepsin B, was strongly inhibited BANA hydrolysis at pH 6.0 under 37℃ condition.