Rat liver lysosomes contain an arylamidase which hydrolyzes valine-β-naphthylamide most rapidly at pH 7.0 among amino acid-β-naph-thylamides tested. The enzyme was eluted in a position of molecular weight of 150,000 and separated from cathepsin H by gel filtration on Sephacryl S- 200. The enzyme was distinguished into seven types having different isoelectric points under isoelectric focusing. These enzymes exhibit maximum activitites in the neutral pH region for the hydrolysis of valine-β-naphthylamide. They appear to be all cysteine proteases since they are inhibited by sulfhydrylblocking ...
