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Redox Regulation of -Glutamyl Transpeptidase

¹ School of Natural Science, University of California at Merced, Merced, California

Correspondence and requests for reprints should be addressed to Henry Jay Forman, Ph.D., School of Natural Sciences, University of California, Merced, P.O. Box 2039, Merced, CA 95340. E-mail: hjforman{at}gmail.com

Abstract

-Glutamyl transpeptidase (GGT) catalyzes the transfer of the glutamyl moiety from glutathione, and glutathione S-conjugates to acceptors to form another amide or to water to produce free glutamate. Functionally, GGT plays important roles in glutathione homeostasis and mercapturic acid metabolism. The expression of GGT is increased as an adaptive response upon the exposure of oxidative stress. The underlying mechanism of this, however, is nebulous, as GGT gene structure is complex and its transcription is usually controlled by multiple promoters that generate several subtypes of GGT mRNAs. Studies reveal that signaling pathways such as Ras, ERK, p38MAPK, and PI3K are involved in the induction of GGT gene expression in response to oxidative stress. Thus, not surprisingly, induction of GGT mRNA subtypes and the involvement of multiple signaling pathways vary depending on cell type and stimuli.

Key Words: glutathione • signal transduction • oxidative stress • transcription

CLINICAL RELEVANCE -Glutamyl transpeptidase is an important enzyme in the maintenance of the steady-state concentration of glutathione both inside cells and in the extracellular fluids. The enzyme activity is used diagnostically, but abnormal activity, both higher and lower than normal, is a likely contributor in the pathology of diseases in which an oxidative component is involved.

 

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