Glutathione biosynthesis pathway enzymes (GSH biosynthesis enzymes)

The glutathione biosynthesis pathway enzymes, primarily glutamate-cysteine ligase (GCL) and glutathione synthetase (GSS), are responsible for the de novo synthesis of glutathione (GSH), the most abundant intracellular antioxidant [1, 2]. GCL, consisting of catalytic (GCLC) and modifier (GCLM) subunits, catalyzes the rate-limiting step by forming gamma-glutamylcysteine, which GSS then converts to GSH by adding glycine [1, 3]. This pathway is vital for maintaining cellular redox homeostasis, detoxifying reactive oxygen species (ROS), and protecting cells from oxidative damage [3, 4]. In oncology, many tumors upregulate these enzymes to survive oxidative stress and develop resistance to chemotherapy and radiation [3, 5]. Consequently, inhibitors like buthionine sulfoximine (BSO) have been investigated to sensitize tumors by depleting their antioxidant capacity [4, 5]. Conversely, glutathione depletion is a hallmark of neurodegenerative diseases like Parkinson's and Alzheimer's, where the pathway's failure contributes to neuronal death [6]. Therapeutic strategies in these cases involve supplementing with N-acetylcysteine (NAC) to provide the rate-limiting precursor cysteine for GSH production [7]. Overall, these enzymes represent a critical node for modulating cellular survival and response to environmental stressors across various pathologies.

Other names

GSH synthesis pathwayGamma-glutamyl cycle enzymesGlutamate-cysteine ligase and Glutathione synthetaseGlutathione synthesis pathway

Pharmacological modulation involves the competitive inhibition of the rate-limiting enzyme glutamate-cysteine ligase (GCL) to deplete cellular glutathione levels (e.g., in cancer therapy) or the provision of rate-limiting precursors like cysteine to enhance glutathione production (e.g., in oxidative stress-related disorders).