Cysteine
CYSTEINE is a non-essential, sulphur-containing amino acid that is the principal source of sulphur in the diet. As long as methionine and Vitamin B6 are present, all sulphur-rich amino acids can be synthesized by the body since all are converted from methionine and an elemental sulphur. The metabolic steps of this formation is as follows: methionine to cystathionine to cysteine to cystine.
Cysteine's most important function is to contribute to the structure of proteins in the form of cystine. Cysteine is more soluble than cystine and contributes its sulphur more readily. It is also very unstable and easily converted to cystine, especially in the absence of Vitamin C. Cystine sometimes forms kidney or bladder stones. At least three times the dose of Vitamin C should accompany cysteine supplementation.
In chronic diseases, the formation of cysteine from methionine is prevented. Cysteine and methionine are used to form several essential compounds, including coenzyme A, heparin, biotin, lipoic acid, and glutathione. Cysteine is an integral part of the enzyme glutathione peroxidase. However, cysteine's sulfur is often converted to sulfate, a substance that can produce calcium deficiency in people on high protein diets.
Along with glycine, glutamic acid, niacin, and chromium, cysteine is a vital component of the glucose tolerance factor. People with diabetic tendencies should not use large supplemental doses of cysteine, unless under supervision, as it is capable of inactivating insulin.
Cysteine also helps to detoxify harmful toxins, thereby protecting and preserving the cells. Cysteine has a chelating effect, removing excess copper from the body. It is a powerful antioxidant; and, when combined with Vitamins C and B1 (Thiamin), has a protective effect on cells exposed to radiation. It also protects the liver and brain from damage caused by alcohol and cigarette smoke. It is one of the best free radical destroyers, and works best when taken with selenium and Vitamin E.
Cysteine is found in abundance in such proteins as hair keratin, insulin, and digestive enzymes (chromotrypsinogen A, trypsinogen, papain, and lactoglobulin). Skin flexibility and texture is influenced by cysteine as it has the ability to slow abnormal crosslinkages in collagen. Because of its ability to break down mucus in the respiratory tract, cysteine is often beneficial in the treatment of bronchitis, emphysema, and tuberculosis.
Homocysteine (HCY) is a toxic amino acid produced during the course of methionine metabolism. In order for homocysteine to be of any use in the body, it must be broken down quickly into other components, including cysteine. Deficient levels of B6, B12, and folate can prevent any rapid conversion producing toxic effects. Derived mainly from pasteurized cow's milk and red meat, homocysteine is a major cause of arterial lesions that make the blood more prone to clotting and producing fatty buildup. It is reported that supplements of B6, choline, and folate can lower HCY levels by 32% in just 3 weeks. (Fluoride also increases HCY levels).
Other names for cysteine include: CYS, amino acid C, and 2-amino-3-mercatopropanoic acid.
Deficiency symptoms include: decreased immunity, deterioration of hair and fingernail growth, premature ageing, and an overall decreased protein uptake.
