Glutathione is a compound synthesized from cysteine, perhaps the most important member of the body's toxic waste disposal team. Like cysteine, glutathione contains the crucial thiol (-SH) group that makes it an effective antioxidant. There are virtually no living organisms on this planet-animal or plant whose cells don't contain some glutathione. Scientists have speculated that glutathione was essential to the very development of life on earth. glutathione has many roles; in none does it act alone. It is a coenzyme in various enzymatic reactions. The most important of these are redox reactions, in which the thiol grouping on the cysteine portion of cell membranes protects against peroxidation; and conjugation reactions, in which glutathione (especially in the liver) binds with toxic chemicals in order to detoxify them. glutathione is also important in red and white blood cell formation and throughout the immune system. glutathione's clinical uses include the prevention of oxygen toxicity in hyperbaric oxygen therapy, treatment of lead and other heavy metal poisoning, lowering of the toxicity of chemotherapy and radiation in cancer treatments, and reversal of cataracts. (http://www.dcnutrition.com/AminoAcids/) glutathione participates in leukotriene synthesis and is a cofactor for the enzyme glutathione peroxidase. It is also important as a hydrophilic molecule that is added to lipophilic toxins and waste in the liver during biotransformation before they can become part of the bile. glutathione is also needed for the detoxification of methylglyoxal, a toxin produced as a by-product of metabolism. This detoxification reaction is carried out by the glyoxalase system. Glyoxalase I (EC 4.4.1.5) catalyzes the conversion of methylglyoxal and reduced glutathione to S-D-Lactoyl-glutathione. Glyoxalase II (EC 3.1.2.6) catalyzes the hydrolysis of S-D-Lactoyl-glutathione to glutathione and D-lactate. GSH is known as a substrate in both conjugation reactions and reduction reactions, catalyzed by glutathione S-transferase enzymes in cytosol, microsomes, and mitochondria. However, it is also capable of participating in non-enzymatic conjugation with some chemicals, as in the case of n-acetyl-p-benzoquinone imine (NAPQI), the reactive cytochrome P450-reactive metabolite formed by acetaminophen, that becomes toxic when GSH is depleted by an overdose (of acetaminophen). glutathione in this capacity binds to NAPQI as a suicide substrate and in the process detoxifies it, taking the place of cellular protein thiol groups which would otherwise be covalently modified; when all GSH has been spent, NAPQI begins to react with the cellular proteins, killing the cells in the process. The preferred treatment for an overdose of this painkiller is the administration (usually in atomized form) of N-acetylcysteine, which is used by cells to replace spent GSSG and renew the usable GSH pool. (http://en.wikipedia.org/wiki/glutathione).