Cysteine is found extensively in the plant foods human ingest. It is found plentifully in the grasses and thus in the meat of domesticated grazing animals.
Chemically very reactive, cysteine is a sulfur containing amino acid that is unique of its chemistry sulfhydryl group.
Cysteine takes its name from cystine, named after the Greek kustis meaning bladder – cystine was first isolated for kidney stones.
Cysteine, in the presence of mild oxidizing agents, readily dimerizes, that is reacts with another cysteine molecule to form a cysteine molecule.
The sulfur in cysteine molecules plays a crucial role in folding proteins into their correct shapes. For examples sulfur independent proteins are keratin – part of hair, skin and nails and collagen – part of connective tissue like cartilage.
In addition, cysteine is a precursor of methionine and also thiamine, biotin, lipoic acid, coenzymes A and coenzyme M.
The amino acid contains a sulfur group that help to function as antioxidant. Cysteine also can be combined with glutamic acid and glycine in liver cells to form glutathione, which is a principle water soluble antioxidant in cells and the blood.
The human body synthesizes the amino acid cysteine for homocysteine and it is part of human hair, skin and nails as the protein keratin.
Cysteine can be found in red pepper, garlic, onions, broccoli, brussel sprouts, oats and wheat germ.
It is used by bakers to break up the gluten in flour, thus recuing its stickiness and facilitating the kneading of the dough.
Due to their high reactivity, cysteine and its derivatives such as acetylcysteine are also used in expectorants.
What is cysteine?
