This family of peptidase inhibitors is expressed from plasmodial protozoal species. Falstatin is found to be a potent reversible inhibitor of the P. falciparum cysteine proteases falcipain-2 and falcipain-3, as well as other parasite- and non-parasite-derived cysteine proteases, but is only a relatively weak inhibitor of the P. falciparum cysteine proteases falcipain-1 and dipeptidyl aminopeptidase 1. Thus, P. falciparum requires expression of falstatin to limit proteolysis by certain host or parasite cysteine proteases during erythrocyte invasion.

1: Falstatin, a cysteine protease inhibitor of Plasmodium falciparum, facilitates erythrocyte invasion. Pandey KC, Singh N, Arastu-Kapur S, Bogyo M, Rosenthal PJ; PLoS Pathog. 2006;2:e117. PMID:17083274