Structural basis for natural lactonase and promiscuous phosphotriesterase activities

J Mol Biol. 2008 Jun 20;379(5):1017-28. doi: 10.1016/j.jmb.2008.04.022. Epub 2008 Apr 16.


Organophosphates are the largest class of known insecticides, several of which are potent nerve agents. Consequently, organophosphate-degrading enzymes are of great scientific interest as bioscavengers and biodecontaminants. Recently, a hyperthermophilic phosphotriesterase (known as SsoPox), from the Archaeon Sulfolobus solfataricus, has been isolated and found to possess a very high lactonase activity. Here, we report the three-dimensional structures of SsoPox in the apo form (2.6 A resolution) and in complex with a quorum-sensing lactone mimic at 2.0 A resolution. The structure also reveals an unexpected active site topology, and a unique hydrophobic channel that perfectly accommodates the lactone substrate. Structural and mutagenesis evidence allows us to propose a mechanism for lactone hydrolysis and to refine the catalytic mechanism established for phosphotriesterases. In addition, SsoPox structures permit the correlation of experimental lactonase and phosphotriesterase activities and this strongly suggests lactonase activity as the cognate function of SsoPox. This example demonstrates that promiscuous activities probably constitute a large and efficient reservoir for the creation of novel catalytic activities.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution
  • Apoenzymes / chemistry
  • Apoenzymes / genetics
  • Apoenzymes / metabolism
  • Base Sequence
  • Biodegradation, Environmental
  • Carboxylic Ester Hydrolases / chemistry
  • Carboxylic Ester Hydrolases / genetics
  • Carboxylic Ester Hydrolases / metabolism
  • Catalytic Domain / genetics
  • Crystallography, X-Ray
  • DNA Primers / genetics
  • DNA, Archaeal / genetics
  • Insecticides / metabolism
  • Kinetics
  • Lactones / metabolism
  • Models, Molecular
  • Mutagenesis, Site-Directed
  • Organophosphates / metabolism
  • Phosphoric Triester Hydrolases / chemistry*
  • Phosphoric Triester Hydrolases / genetics
  • Phosphoric Triester Hydrolases / metabolism
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Spectrometry, X-Ray Emission
  • Sulfolobus solfataricus / enzymology
  • Sulfolobus solfataricus / genetics


  • Apoenzymes
  • DNA Primers
  • DNA, Archaeal
  • Insecticides
  • Lactones
  • Organophosphates
  • Recombinant Proteins
  • Carboxylic Ester Hydrolases
  • N-acyl homoserine lactonase
  • Phosphoric Triester Hydrolases