Enzymes of the glutathione synthetic pathway (GCL/GSS)

The enzymes of the glutathione synthetic pathway, primarily glutamate-cysteine ligase (GCL) and glutathione synthetase (GSS), are responsible for the de novo biosynthesis of glutathione (GSH), the cell's most abundant antioxidant (NIH, 2023). GCL is the rate-limiting enzyme and consists of a catalytic subunit (GCLC) and a modifier subunit (GCLM), while GSS completes the synthesis by adding glycine (NIH, 2019). This pathway plays a critical role in maintaining cellular redox homeostasis, protecting against oxidative stress, and detoxifying various xenobiotics and drugs (NIH, 2023). In oncology, many tumors upregulate these enzymes to maintain low levels of reactive oxygen species (ROS) and resist the effects of chemotherapy and radiation (NIH, 2021). Consequently, inhibiting these enzymes with drugs like buthionine sulfoximine (BSO) is a strategy to deplete GSH and sensitize cancer cells to treatment or induce ferroptosis (Wikipedia, 2024; NIH, 2023). Conversely, impaired activity of these enzymes is associated with neurodegenerative conditions like Parkinson's disease and certain metabolic disorders, highlighting their importance in systemic health (NIH, 2025). The pathway is also integrated with the gamma-glutamyl cycle, which facilitates amino acid transport and GSH recycling (NIH, 2023).

Other names

Glutathione biosynthetic enzymesGSH synthesis enzymesGamma-glutamylcysteine synthetaseGlutamate-cysteine ligaseGlutathione synthetaseGCLGSS

Inhibition of the rate-limiting enzyme glutamate-cysteine ligase (GCL) to deplete intracellular glutathione (GSH) levels, thereby increasing oxidative stress and sensitizing cells to apoptosis or ferroptosis.