SPECIFIC ASSAY-METHOD FOR THE ACTIVITIES OF CATHEPSIN L-TYPE CYSTEINEPROTEINASES

We have established a new differential assay method for cathepsin L-ty pe proteinases using specific inhibitors, E-64 for all cysteine protei nases, CA-074 for cathepsin B, and PLCPI for cathepsin L-type proteina ses with Z-Phe-Arg-MCA as the substrate. The value of cathepsin B calc ulated by this method did not coincide with value assayed directly in terms of the hydrolysis of Z-Arg-Arg-MCA, a specific substrate for cat hepsin B. The activities of cathepsin L-type proteinases, cathepsins B and J in rat liver and kidney were assayed at the same time using thi s new assay method as a representative example.