Abstract for presentation at 11th International Congress of Human Genetics

An Ethnic-Specific Polymorphism in Glutamate Cysteine Ligase Abolishes In Vitro Production of Glutathione Intermediates

  • Dr Truc Le, Division of Pediatric Critical Care Medicine, Vanderbilt Children's Hospital, Nashville, TN, United States
  • Dr Frederick Barr, Division of Pediatric Critical Care Medicine, Vanderbilt Children's Hospital, Nashville, TN, United States
  • Dr Alecia Willis, epartment of Genetics, Johns Hopkins University, Baltimore, MD, United States
  • Dr Marshall Summar, Division of Medical Genetics, Vanderbilt University, Nashville, TN, United States

    • Background: Glutathione plays a crucial role in free radical scavenging, oxidative injury, and cellular homeostasis. Glutamate cysteine ligase (GCL) is the rate-limiting enzyme in the glutathione biosynthesis pathway. Polymorphisms within the gene encoding the catalytic subunit (GCLC) can potentially affect an individual's ability to produce glutathione and respond to oxidative injury. Previously, we have identified 11 polymorphisms in the gene encoding GCLC and demonstrated that following cardiac bypass, some of these polymorphisms are associated with an increased incidence of pulmonary hypertension as well as increased markers of oxidative injury. Of note, only one of the identified polymorphisms was a nonsynonymous polymorphism (C1384T). Additionally, this polymorphism was only found in individuals of African descent.
    Objective: To determine the effect of the C1384T polymorphism on the enzymatic activity of GCLC in vitro.
    Methods: Wild-type GCLC enzyme and the GCLC enzyme containing the C1384T polymorphism were expressed using a bacterial protein expression system. The expressed enzymes were used in an in vitro assay to produce gamma-glutamylcysteine (y-GC), a glutathione intermediate. After completion of the assay, y-GC levels were measured using 2 independent methods.
    Results: Wild-type GCLC enzyme and the C1384T-modified variant were used to perform an in vitro assay to produce y-GC. After completion of the assay, there was no detectable production of y-GC by the C1384T-modified variant enzyme as compared to the wild-type enzyme.
    Conclusions: A nonsynonymous, ethnic-specific polymorphism in the GCLC gene produces an enzyme with no detectable production of glutathione intermediates in vitro. The discovery of this ethnic-specific polymorphism that encodes an enzyme with null activity indicates that certain segments of the population of African descent may be predisposed to glutathione depletion and increased cellular injury following oxidative stress.

    Conference Organiser - ICMS Pty Ltd