Cathepsin B is present in situ withinthe pH 5.5 environment of secretory vesicles that produce peptideneurotransmitters.60 The two neuroblastomacell lines showed similar specific activities of cathepsin B. Themicroglial cells displayed high cathepsin B specific activity thatwas 2 to 4 times higher than that of the neuroblastoma cells dependingon the pH. The gene discussed is CTSB; the disease is neuroblastoma.