Cysteine is a naturally occurring hydrophobic amino acid which has a sulfhydryl group and is found in most proteins, however only in small quantities. 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: -CH₂-SH; hydrophobic

Mass: 121.16

Isoelectric point: 5.05

See also

• selenocysteine
• amino acids
• thiols

External links

• http://www.chemie.fu-berlin.de/chemistry/bio/aminoacid/cystein_en.html
• On the hydrophobic nature of cysteine.