Cysteine
Cysteine is a sulphur-containing amino acid and the building block that gives glutathione its working thiol group. Its supply is one of the two key controls on how fast cells make glutathione.
Also called L-cysteine, Cys.
The availability of cysteine, together with the activity of glutamate cysteine ligase, is a key determinant of glutathione synthesis (Lu 2013).
Outside cells much of it exists as cystine, two cysteines joined, which cells must bring in and split. When cystine was removed from their culture medium, human cartilage cells lost glutathione and became more vulnerable to oxidant-driven death (Del Carlo 2003).
In older adults, red-cell cysteine and glutathione were both lower than in younger adults, and two weeks of cysteine and glycine raised glutathione by about 95% (Sekhar 2011). Trials commonly supply it as N-acetylcysteine (NAC), a more stable form, as in the GlyNAC trials in older adults (Kumar 2023).
Sources
- Lu SC. Glutathione synthesis. Biochim Biophys Acta 2013.
- Carlo MD Jr, Loeser RF. Increased oxidative stress with aging reduces chondrocyte survival: correlation with intracellular glutathione levels. Arthritis Rheum 2003.
- Sekhar RV, Patel SG, Guthikonda AP et al. Deficient synthesis of glutathione underlies oxidative stress in aging and can be corrected by dietary cysteine and glycine supplementation. Am J Clin Nutr 2011.
- Kumar P, Liu C, Suliburk J et al. Supplementing Glycine and N-Acetylcysteine (GlyNAC) in Older Adults Improves Glutathione Deficiency, Oxidative Stress, Mitochondrial Dysfunction, Inflammation, Physical Function, and Aging Hallmarks: A Randomized Clinical Trial. J Gerontol A Biol Sci Med Sci 2023.
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