Prolyl Oligopeptidase from the Blood Fluke Schistosoma mansoni: From Functional Analysis to Anti-schistosomal Inhibitors

PLoS Negl Trop Dis. 2015 Jun 3;9(6):e0003827. doi: 10.1371/journal.pntd.0003827. eCollection 2015.


Background: Blood flukes of the genus Schistosoma cause schistosomiasis, a parasitic disease that infects over 240 million people worldwide, and for which there is a need to identify new targets for chemotherapeutic interventions. Our research is focused on Schistosoma mansoni prolyl oligopeptidase (SmPOP) from the serine peptidase family S9, which has not been investigated in detail in trematodes.

Methodology/principal findings: We demonstrate 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. Recombinant SmPOP was produced in Escherichia coli and its active site specificity investigated using synthetic substrate and inhibitor libraries, and by homology modeling. SmPOP is a true oligopeptidase that hydrolyzes peptide (but not protein) substrates with a strict specificity for Pro at P1. The inhibition profile is analogous to those for mammalian POPs. Both the recombinant enzyme and live worms cleave host vasoregulatory, proline-containing hormones such as angiotensin I and bradykinin. Finally, we designed nanomolar inhibitors of SmPOP that induce deleterious phenotypes in cultured schistosomes.

Conclusions/significance: We provide the first localization and functional analysis of SmPOP together with chemical tools for measuring its activity. We briefly discuss the notion that SmPOP, operating at the host-parasite interface to cleave host bioactive peptides, may contribute to the survival of the parasite. If substantiated, SmPOP could be a new target for the development of anti-schistosomal drugs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Catalytic Domain / genetics
  • DNA Primers / genetics
  • Escherichia coli
  • Gene Expression Profiling
  • Gene Expression Regulation, Enzymologic / physiology*
  • Hydrolysis
  • Immunoblotting
  • Microscopy, Fluorescence
  • Models, Molecular*
  • Real-Time Polymerase Chain Reaction
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism*
  • Schistosoma mansoni / enzymology*
  • Serine Endopeptidases / genetics
  • Serine Endopeptidases / metabolism*
  • Substrate Specificity


  • DNA Primers
  • Recombinant Proteins
  • Serine Endopeptidases
  • prolyl oligopeptidase

Grant support

This work was supported by the grant P302/11/1481 from Czech Science Foundation (, the project InterBioMed LO1302 from the Ministry of Education, Youth and Sports of the Czech Republic and by the institutional project RVO 61388963 ( LU was partially supported by the Sciex-NMS grant 11.222 from CRUS Switzerland. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.