Prolyl Oligopeptidase from the Blood Fluke Schistosoma mansoni: designing active-site inhibitors with anti-schistosomal activity

Pavla Fajtová1, Saša Štefanić2, Martin Hradilek1, Jan Dvořák1,3, Jiří Vondrášek1, Adéla Jílková1, Lenka Ulrychová1, James H. McKerrow4, Conor R. Caffrey4, Michael Mareš1, Martin Horn1*

1Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nam. 2, Prague, Czech Republic, *
2Institute of Parasitology, University of Zurich, Winterthurerstrasse 266, Zurich, Switzerland
3School of Biological Sciences, Queen´s University Belfast, 97 Lisburn Road, Belfast, United Kingdom
4Skaggs School of Pharmacy and Pharmaceutical Sciences, 9500 Gilman Drive, University of California San Diego, California, USA


Blood flukes of the genus Schistosoma cause schistosomiasis, a parasitic disease that infects over 240 million people worldwide, and there is a need to identify new targets for chemotherapeutic interventions. Schistosoma mansoni prolyl oligopeptidase (SmPOP) from the serine peptidase family S9 has not been investigated in detail, so far. We demonstrated that SmPOP is expressed in adult worms and schistosomula in an enzymatically active form. By immunofluorescence microscopy, SmPOP is localized in the tegument and parenchyma of both developmental stages. SmPOP was produced in the bacterial expression system and its active site specificity was investigated using synthetic substrate libraries and a SmPOP homology model. SmPOP is a true oligopeptidase that hydrolyzes peptide (but not protein) substrates with a strict specificity for Pro at P1. Both the recombinant enzyme and live worms cleave host vasoregulatory, proline-containing hormones such as angiotensin and bradykinin. Finally, we designed nanomolar inhibitors of SmPOP that are effective against schistosomes. Our results suggest that SmPOP plays a role in host-parasite interactions and is a potential target for the development of anti-schistosomal drugs.