Glutathione (GSH) is a tripeptide antioxidant that reduces disulfide bonds between cytoplasmic proteins. The constitutive enzyme glutathione reductase transforms glutathione into its reduced state, which ultimately can provide a measure of cellular toxicity. GSTCD (glutathione S-transferase, C-terminal domain containing) is a 633 amino acid protein belonging to the GSTCD family and contains one GST C-terminal domain. The gene encoding GSTCD maps to human chromosome 4, which represents approximately 6% of the human genome and contains nearly 900 genes. Notably, the Huntingtin gene, which is found to encode an expanded glutamine tract in cases of Huntington's disease, is on chromosome 4. FGFR-3 is also encoded on chromosome 4 and has been associated with thanatophoric dwarfism, achondroplasia, Muenke syndrome and bladder cancer. Chromosome 4 is also tied to Ellis-van Creveld syndrome, methylmalonic acidemia and polycystic kidney disease.