Glutathione biosynthetic pathway (GSH pathway)

The glutathione biosynthetic pathway is a fundamental metabolic route responsible for the de novo synthesis of glutathione (GSH), a tripeptide (gamma-glutamyl-cysteinyl-glycine) that serves as the primary endogenous antioxidant in eukaryotic cells (Lu, 2013). The pathway consists of two ATP-dependent steps: the first and rate-limiting step is catalyzed by glutamate-cysteine ligase (GCL), which forms gamma-glutamylcysteine from glutamate and cysteine, and the second step is catalyzed by glutathione synthetase (GS), which adds glycine to the intermediate (NIH). GSH plays a vital role in maintaining cellular redox homeostasis, detoxifying electrophilic xenobiotics through conjugation, and acting as a cofactor for various enzymes like glutathione peroxidase (PubChem). In many cancers, this pathway is upregulated to protect malignant cells from high levels of reactive oxygen species (ROS) and to confer resistance against platinum-based chemotherapy and radiation (Traverso et al., 2013). Conversely, a deficiency in GSH is linked to neurodegenerative diseases like Parkinson's and Alzheimer's, as well as chronic liver diseases (StatPearls). Therapeutic strategies include the use of buthionine sulfoximine (BSO) to inhibit GCL and deplete GSH in tumors, or the administration of N-acetylcysteine (NAC) to provide the rate-limiting precursor cysteine for GSH replenishment in cases of toxicity or oxidative stress (PubMed).

Other names

GSH synthesis pathwayGamma-glutamyl cycle (synthesis phase)De novo glutathione synthesis

The pathway is modulated by either inhibiting the rate-limiting enzyme glutamate-cysteine ligase (GCL) to deplete glutathione (GSH) levels, primarily in oncology to overcome chemoresistance, or by supplementing the pathway with precursors like N-acetylcysteine (NAC) to restore GSH levels in conditions of oxidative stress or toxicity.