L-Cysteine
Introduction
Section titled “Introduction”L-cysteine is a sulfur-containing, semi-essential amino acid, meaning that while the human body can synthesize it from other amino acids like methionine, dietary intake can be beneficial, especially under certain physiological conditions. It is a fundamental building block for proteins and plays a crucial role in numerous biological processes essential for maintaining cellular health and overall bodily function.
Biological Basis
Section titled “Biological Basis”Biologically, L-cysteine is indispensable for its contributions to protein structure and antioxidant defense. It is a key precursor for the synthesis of glutathione, a potent antioxidant tripeptide that protects cells from damage caused by free radicals and oxidative stress.[1]The unique thiol group in L-cysteine enables the formation of disulfide bonds, which are critical for stabilizing the three-dimensional structure and functional activity of many proteins. Furthermore, L-cysteine participates in various detoxification pathways within the body. As an important endogenous metabolite, its levels and metabolic pathways are extensively studied in metabolomics, a field that aims to comprehensively measure metabolites and understand how genetic variants influence their homeostasis.[2]
Clinical Relevance
Section titled “Clinical Relevance”The diverse biological roles of L-cysteine have significant clinical implications. Its central role in glutathione metabolism links it to conditions involving oxidative stress and inflammation. Genetic variations affecting amino acid metabolism, including those related to L-cysteine pathways, can influence an individual’s overall physiological state.[2] For example, studies have identified associations between genetic variants and biomarkers such as cystatin C (CST3), a protein primarily used as a marker for kidney function and also potentially indicative of cardiovascular disease risk.[3]Specifically, single nucleotide polymorphisms (SNPs) near theCST3 gene, such as rs1158167 , have been significantly associated with variations in cystatin C levels. [3] Additionally, enzymes like gamma-glutamyl transferase, which are integral to glutathione metabolism, have shown interesting signals in genome-wide association studies, underscoring the interconnectedness of these biochemical pathways and their impact on health. [4]
Social Importance
Section titled “Social Importance”L-cysteine holds social importance through its natural presence in the diet and its widespread use in health supplements. It is found in various high-protein foods, and its derivative, N-acetylcysteine (NAC), is a common supplement valued for its antioxidant and mucolytic properties. Understanding the genetic factors that influence L-cysteine metabolism and related pathways can contribute to the development of personalized nutrition strategies and targeted therapeutic interventions. This knowledge has the potential to impact public health by addressing conditions linked to oxidative stress, detoxification processes, and overall metabolic balance.
Key Variants
Section titled “Key Variants”| RS ID | Gene | Related Traits |
|---|---|---|
| rs7519001 | SRP14P4 - GM2AP2 | L-Cysteine measurement |
References
Section titled “References”[1] Melzer, David, et al. “A Genome-Wide Association Study Identifies Protein Quantitative Trait Loci (pQTLs).” PLoS Genet, vol. 4, no. 5, 2008, p. e1000072.
[2] Gieger, Christian, et al. “Genetics Meets Metabolomics: A Genome-Wide Association Study of Metabolite Profiles in Human Serum.”PLoS Genet, vol. 5, no. 11, 2009, p. e1000694.
[3] Hwang, Shih-Jen, et al. “A Genome-Wide Association for Kidney Function and Endocrine-Related Traits in the NHLBI’s Framingham Heart Study.” BMC Med Genet, vol. 8, no. Suppl 1, 2007, p. S10.
[4] Wallace, Cathryn, et al. “Genome-Wide Association Study Identifies Genes for Biomarkers of Cardiovascular Disease: Serum Urate and Dyslipidemia.”Am J Hum Genet, vol. 82, no. 1, 2008, pp. 139–49.