Metabolism of glutamine and glutathione via gamma-glutamyltranspeptidase and glutamate transport in Helicobacter pylori: possible significance in the pathophysiology of the organism

Mol Microbiol. 2007 Apr;64(2):396-406. doi: 10.1111/j.1365-2958.2007.05661.x. Epub 2007 Mar 23.


gamma-Glutamyltranspeptidase (GGT) is a periplasmic enzyme of Helicobacter pylori implicated in its pathogenesis towards mammalian cells. We have cloned and expressed the H. pylori strain 26695 recombinant GGT protein in Escherichia coli and purified it to homogeneity. The purified protein exhibited hydrolysis activity with very high affinities for glutamine and glutathione shown by apparent K(m) values lower than 1 muM. H. pylori cells were unable to take up extracellular glutamine and glutathione directly. Instead, these substances were hydrolysed to glutamate by the action of GGT outside the cells. The glutamate produced was then transported by a Na(+)-dependent reaction into H. pylori cells, where it was mainly incorporated into the TCA cycle and partially utilized as a substrate for glutamine synthesis. These observations show that one of the principle physiological functions of H. pylori GGT is to enable H. pylori cells to utilize extracellular glutamine and glutathione as a source of glutamate. As glutamine and glutathione are important nutrients for maintenance of healthy gastrointestinal tissue, their depletion by the GGT enzyme is hypothesized to account for the damaging of mammalian cells and the pathophysiology of H. pylori.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Transport Systems, Acidic / metabolism*
  • Catalysis
  • Cloning, Molecular
  • Cytosol / metabolism
  • Electrophoresis, Polyacrylamide Gel
  • Enzyme Activation
  • Glutamic Acid / metabolism*
  • Glutamine / metabolism*
  • Glutathione / metabolism*
  • Helicobacter pylori / cytology
  • Helicobacter pylori / enzymology*
  • Helicobacter pylori / pathogenicity*
  • Hydrogen-Ion Concentration
  • Hydrolysis
  • Kinetics
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism
  • Substrate Specificity
  • gamma-Glutamyltransferase / isolation & purification
  • gamma-Glutamyltransferase / metabolism*


  • Amino Acid Transport Systems, Acidic
  • Recombinant Proteins
  • Glutamine
  • Glutamic Acid
  • gamma-Glutamyltransferase
  • Glutathione