Induction and inhibition of cathepsin B and hemoglobin-hydrolase activity in murine B16 melanoma by thiol protease inhibitors

The effects of potent thiol protease inhibitors in vitro (leupeptin, antipain, chymostatin and E-64 (N-[N-(L-3-trans-carboxyoxirane-2-carbonyl)-L-leucyl]agmatine) on intracellular cathepsin B and hemoglobin (Hb)-hydrolase from cultured B16 melanoma cells were studied. E-64 induced cultured B16 melanoma cells to decrease the activities of intracellular cathepsin B (EC 3.4.22.1.) but did not have this effect with Hb-hydrolase or acid phosphatase (EC 3.1.3.2). Leupeptin, antipain and chymostatin induced B16 melanoma cells to increase the activities of intracellular cathepsin B and Hb-hydrolase but not that of acid phosphatase. These results indicate that there are two kinds of thiol protease inhibitors, each with a varying reaction to cultured B16 melanoma--inhibition of intracellular cathepsin B, and conversely, inducement of both cathepsin B and Hb-hydrolase.