Cysteine is a naturally occurring hydrophilic ("water loving") amino acid which has a sulfhydryl (SH) group and is found in most proteins. When it is exposed to air it oxidizes to form cystine, which is two cysteine molecules joined by a disulfide bond. One molecule of water (H₂O) is the byproduct from the creation of each molecule of cystine. It can be taken as a supplement in the form of N-acetylcysteine (NAC).

Symbol: C or Cys

Side chain type: hydrophilic

Mass: 121.16

Isoelectric point: 5.05

External link

• http://www.chemie.fu-berlin.de/chemistry/bio/aminoacid/cystein_en.html