Crystal structure of gamma-chymotrypsin in complex with 7-hydroxycoumarin

J Mol Biol. 2001 Nov 30;314(3):519-25. doi: 10.1006/jmbi.2001.5148.


The 1.8 A crystal structure of 7-hydroxycoumarin (7-HC) bound to chymotrypsin reveals that this inhibitor forms a planar cinnamate acyl-enzyme complex. The phenyl ring of the bound inhibitor forms numerous van der Waals contacts in the S1 pocket of the enzyme, with the p-hydroxyl group donating a hydrogen bond to the main-chain oxygen atom of Ser217, and the o-hydroxyl group forming a water-mediated hydrogen bond with the carbonyl oxygen of Val227. The structure of the acyl-enzyme complex suggests that the mechanism of inhibition of 7-HC involves nucleophilic attack by the Ser195 O(gamma) atom on the carbonyl carbon atom of the inhibitor, accompanied by the breaking of the 2-pyrone ring of the inhibitor, and leading to the formation of a cinnamate acyl-enzyme derivative via a tetrahedral transition state. Comparisons with structures of photoreversible cinnamates bound to chymotrypsin reveal that although 7-HC interacts with the enzyme in a similar fashion, the binding of 7-HC to chymotrypsin takes place in a productive conformation in contrast to the photoreversible cinnamates. In summary, the 7-HC-chymotrypsin complex provides basic insight into the inhibition of chymotrypsin by natural coumarins and provides a structural basis for the design of more potent mechanism-based inhibitors against a wide range of biologically important chymotrypsin-like enzymes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites
  • Cattle
  • Chymotrypsin / antagonists & inhibitors*
  • Chymotrypsin / chemistry*
  • Chymotrypsin / metabolism
  • Cinnamates / chemistry
  • Cinnamates / metabolism
  • Crystallography, X-Ray
  • Drug Design
  • Hydrogen Bonding
  • Models, Chemical
  • Models, Molecular
  • Protein Binding
  • Protein Conformation
  • Serine Proteinase Inhibitors / chemistry*
  • Serine Proteinase Inhibitors / metabolism*
  • Structure-Activity Relationship
  • Umbelliferones / chemistry*
  • Umbelliferones / metabolism*


  • Cinnamates
  • Serine Proteinase Inhibitors
  • Umbelliferones
  • 7-hydroxycoumarin
  • Chymotrypsin
  • gamma-chymotrypsin

Associated data

  • PDB/1K2I