Expression of γ-Glutamyl Transpeptidase Protects Ramos B Cells from Oxidation-induced Cell Death

David R. Karp, Kiyoshi Shimooku, Peter E. Lipsky

Research output: Contribution to journalArticlepeer-review

162 Scopus citations


The ectoenzyme, γ-glutamyl transpeptidase (GGT, EC cleaves glutathione (GSH) to facilitate the recapture of cysteine for synthesis of intracellular GSH. The impact of GGT expression on cell survival during oxidative stress was investigated using the human B cell lymphoblastoid cell line, Ramos. Ramos cells did not express surface GGT and exhibited no GGT enzyme activity. In contrast, Ramos cells stably transfected with the human GGT cDNA expressed high levels of surface GGT and enzymatic activity. GGT-transfected Ramos cells were protected from apoptosis when cultured in cyst(e)ine-deficient medium. The GGT-expressing cells also had lower levels of intracellular reactive oxygen species (ROS). Homocysteic acid and alanine, inhibitors of cystine and cysteine uptake, respectively, caused increased ROS content and diminished viability of GGT expressing cells. Exogenous GSH increased the viability of the GGT-transfected cells more effectively than that of control cells, whereas the products of GSH metabolism prevented death of both the control and GGT-transfected cells comparably. These data indicate that GGT cleavage of GSH and the subsequent recapture of cysteine and cystine allow cells to maintain low levels of cellular ROS and thereby avoid apoptosis induced by oxidative stress.

Original languageEnglish (US)
Pages (from-to)3798-3804
Number of pages7
JournalJournal of Biological Chemistry
Issue number6
StatePublished - Feb 9 2001

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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