Biological Chemistry

Abstract

Recombinant full-length human procathepsin F, produced in the baculovirus expression system, was partially processed during the purification procedure to a form lacking the N-terminal cystatin-like domain and activated with pepsin. Active cathepsin F efficiently hydrolyzed Z-FR-MCA (k/K=106 mM[-1]s[-1]) and Bz FVR-MCA (k/K=8 mM[-1]s[-1]), whereas hydrolysis of Z-RR- MCA was very slow (k/K<0.2 mM[-1]s[-1]). Cathepsin F was rapidly and tightly inhibited by cystatin C, chicken cystatin and equistatin with K values in the subnanomolar range (0.03-0.47 nM), whereas Lkininogen was a less strong inhibitor of the enzyme (K=4.7 nM). Stefin A inhibited cathepsin F slowly (k=1.610exp5 mM[-1]s[-1]) and with a lower affinity (K=25 nM). These data suggest that cathepsin F differs from other related endopeptidases by considerably weaker inhibition by stefins.