Role of γ-glutamyltranspeptidase in detoxification of xenobiotics in the yeasts Hansenula polymorpha and Saccharomyces cerevisiae

GGTI gene of the methylotrophic yeast Hansenula polymorpha appears to be a structural and functional homologue of Saccharomyces cerevisiae CIS2/ECM38 gene encoding gamma-glutamyltranspeptidase (gamma GT). This is confirmed by the absence of the corresponding activity of gamma GT in the mutant with disrupted GGTI gene. It was shown that gamma GT of both H. polymorpha and S. cerevisiae are involved in detoxification of electrophilic xenobiotics, as the corresponding mutants appeared to be defective in the disappearance of the fluorescent vacuolar complex of GSH with xenobiotic bimane and the further diffuse distribution of this complex in the cytosol. We hypothesize that metabolism of electrophilic xenobiotics in the yeasts H. polymorpha and S. cerevisiae occurs through a gamma GT-dependent mercapturic acid pathway of GSH-xenobiotic detoxification, similar to that known for mammalian cells, with cysteine-xenobiotics and/or N-acetylcysteine-xenobiotics as the end products. (c) 2006 International Federation for Cell Biology. Published by Elsevier Ltd. All rights reserved.