The C-terminal domain but not the N-terminal domain of PbICP is a potent inhibitor of cysteine proteases except cathepsin B.

Substrate hydrolysis was measured in the presence of the control protein MBP (1 µM or 100 nM), in the presence of MBP-PbICP-C (1 µM), in the presence of MBP-PbICP-N (1 µM) or in the presence of PbICP-C (100 nM). Protease activity in the presence of 1 µM and 100 nM MBP, respectively was considered as 100% and the percentage of residual protease activity in the presence of the inhibitor was calculated.