Registration Dossier

Administrative data

Link to relevant study record(s)

Description of key information

L-Cysteine, which is the main component of the substance L-Cysteine hydrochloride (monohydrate), is a naturally occuring animo acid. It is mostly a part of proteins. With the digestion of the proteins in the food it can be incorporated into the body or it can be synthezised from precursors in the body. It is metabolized in the normal protein metabolism. 

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential

Additional information

Occurance in Nature

L-Cysteine, which is the main component of the substance L-Cysteine hydrochloride (monohydrate), is widely distributed in the biosphere. The substance is synthesised in living organisms as amino acid and incorporated in proteins. Nevertheless L-Cysteine is the rarest "normal" amino acid in proteins. Often L-Cystein has a specific function in the proteins for example in the redox-reactions of glutathione. Most of the human intake of L-Cysteine is done as part of proteins which are digested into their amino acids and rearranged into new body-specific proteins. According to "Wissenschaftliche Tabellen Geigy, 1979" a concentration of L-Cysteine (MG 121.16) in the blood plasma of 33 µmol/l (= 4 mg/l) was found.