From WikiLectures

Cysteine ​​is a non-essential amino acid that, like methionine , has a sulfur atom in its molecule.

Cysteine ​​molecule

Metabolism cysteine[edit | edit source]

Cysteine ​​synthesis takes place in the human organism from homocysteine ​​and serine .

The degradation of cysteine ​​begins with the oxidation of the -SH group to -SO2- by the enzyme cysteine ​​dioxygenase. In the resulting L-cysteine ​​sulfinate , the -NH2 group is replaced by a keto group with the help of transaminase , and β-sulfinylpyruvate is formed . In the final reaction, it is split by desulfinase into pyruvate and sulfite (SO3-), or final sulfate (SO4-). Cysteine ​​is an important source of taurine . L-cysteine ​​sulfinate is decarboxylated to hypotaurine and subsequent oxidation of the -SO2- - group to -SO3- produces taurine.

Cysteine synthesis

Alternative non-oxidative degradation of cysteine ​​produces pyruvate and sulfane (H2S).

Importance[edit | edit source]

  • In peptides, cysteine ​​is essential for the formation of disulfide bridges.
  • It is a substrate for glutathione.
  • It is a substrate for taurine. The latter is conjugated with bile acids or other substances that increase their solubility in water.
  • Decarboxylation of cysteine ​​produces cysteamine , which is part of coenzyme A.
  • It has a high proportion of keratin protein (hair, nails).

Links[edit | edit source]

Related articles[edit | edit source]


References[edit | edit source]

  • MATOUŠ, Bohuslav, et al. Fundamentals of medical chemistry and biochemistry. 2010 edition. Prague: Galen, 2010. 0 pp.  ISBN 978-80-7262-702-8 .