Glutathione­degrading enzymes in the complex landscape of tumors (Review).

ABSTRACT

Glutathione (GSH)­degrading enzymes are essential for starting the first stages of GSH degradation. These enzymes include extracellular γ­glutamyl transpeptidase (GGT) and intracellular GSH­specific γ­glutamylcyclotransferase 1 (ChaC1) and 2. These enzymes are essential for cellular activities, such as immune response, differentiation, proliferation, homeostasis regulation and programmed cell death. Tumor tissue frequently exhibits abnormal expression of GSH­degrading enzymes, which has a key impact on the development and spread of malignancies. The present review summarizes gene and protein structure, catalytic activity and regulation of GSH­degrading enzymes, their vital roles in tumor development (including regulation of oxidative and endoplasmic reticulum stress, control of programmed cell death, promotion of inflammation and tumorigenesis and modulation of drug resistance in tumor cells) and potential role as diagnostic biomarkers and therapeutic targets.