Arresting tissue invasion of a parasite by protease inhibitors chosen with the aid of computer modeling

Biochemistry. 1991 Nov 26;30(47):11221-9. doi: 10.1021/bi00111a005.


Computer modeling of the three-dimensional structure of an enzyme, based upon its primary sequence alone, is a potentially powerful tool to elucidate the function of enzymes as well as design specific inhibitors. The cercarial (larval) protease from the blood fluke Schistosoma mansoni is a serine protease hypothesized to assist the schistosome parasite in invading the human circulatory system via the skin. A three-dimensional model of the protease was built, taking advantage of the similarity of the sequence of the cercarial enzyme to the trypsin-like class of serine proteases. A large hydrophobic S-1 binding pocket, suspected from previous kinetic studies, was located in the model and confirmed by new kinetic studies with both synthetic peptide substrates and inhibitors. Unexpected structural characteristics of the enzyme were also predicted by the model, including a large S-4 binding pocket, again confirmed by assays with synthetic peptides. The model was then used to design a peptide inhibitor with 4-fold increased solubility, and a series of synthetic inhibitors were tested against live cercariae invading human skin to confirm that predictions of the model were also applicable in a biologic assay.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Computer Simulation
  • Humans
  • Larva
  • Molecular Sequence Data
  • Oligopeptides / metabolism
  • Protease Inhibitors / chemistry
  • Protease Inhibitors / pharmacology*
  • Protein Conformation
  • Schistosoma mansoni / drug effects
  • Schistosoma mansoni / pathogenicity*
  • Sequence Homology, Nucleic Acid
  • Serine Endopeptidases / metabolism*
  • Serine Proteinase Inhibitors / chemistry
  • Serine Proteinase Inhibitors / pharmacology*
  • Skin / parasitology*
  • Substrate Specificity


  • Oligopeptides
  • Protease Inhibitors
  • Serine Proteinase Inhibitors
  • Serine Endopeptidases