Cellular glutathione synthesis pathway (GSH synthesis pathway)

The cellular glutathione synthesis pathway is a fundamental metabolic process responsible for the de novo production of glutathione (GSH), a tripeptide that serves as the primary endogenous antioxidant in mammalian cells (Lu, 2013 [1]). The pathway consists of two sequential ATP-dependent reactions: first, the rate-limiting formation of gamma-glutamylcysteine from glutamate and cysteine by glutamate-cysteine ligase (GCL), and second, the addition of glycine by glutathione synthetase (GSS) (Forman et al., 2009 [2]). GSH is essential for maintaining cellular redox balance, detoxifying reactive oxygen species (ROS), and regulating various signaling pathways including ferroptosis (Dixon et al., 2012 [4]). In oncology, many tumors upregulate this pathway to survive high levels of oxidative stress and resist therapy, making components like GCL or the upstream cystine transporter (System Xc-) attractive targets for sensitization (Kennedy et al., 2020 [3]). Conversely, enhancing this pathway through precursors like N-acetylcysteine is explored for treating conditions characterized by GSH depletion, such as acetaminophen toxicity and certain neurodegenerative diseases (Lu, 2013 [1]). Pharmacological modulation of this pathway, such as the inhibition of GCL by buthionine sulfoximine, aims to sensitize tumor cells to oxidative stress or induce ferroptosis (Dixon et al., 2012 [4]). The pathway also involves the transport of precursors, most notably the uptake of cystine via the System Xc- transporter, which is often the limiting factor for synthesis in many cell types (Dixon et al., 2012 [4]).

Other names

Glutathione biosynthesisGSH synthesisGamma-glutamyl cycle (biosynthetic component)De novo glutathione synthesis

The pathway is modulated by inhibiting the rate-limiting enzyme glutamate-cysteine ligase (GCL) to deplete glutathione, blocking the cystine/glutamate antiporter (System Xc-) to starve the cell of the precursor cysteine, or providing cysteine prodrugs like N-acetylcysteine to replenish glutathione stores (Lu, 2013 [1]; Dixon et al., 2012 [4]).