ISOLATION AND ACTIVATION OF CATHEPSIN L-INHIBITOR COMPLEX FROM PACIFIC WHITING (MERLUCCIUS-PRODUCTUS)

Cathepsin L from Pacific whiting was separated into two activity peaks (P-I and P-II) on butyl-Sepharose. Acidification of the fractions at pH 3.3 resulted in an 11-fold increase in activity of P-I and a slight decrease in P-II on Z-Phe-Arg-NMec, suggesting that P-I is complex-formed with an inhibitor while P-II is the free enzyme. Analysis of further purified DEAF P-I fractions showed. that only 55% of the activity was titrated by E-64 while low-pH-treated fractions were completely titrated. The DEAE P-I fractions showed highest pH stability at pH 4, while acidified DEAF: P-I fractions showed the highest stability at pH 7.0.