Cystine (inci)

Cystine (this usually refers to L-cystine), a disulfide of cysteine, is a natural, proteinogenic amino acid. It occurs in high concentrations, peptide-bound, mainly in skin and hair. Cystine is formed by oxidation of 2 L-cysteine residues. The disulfide bridges (see structural formula) contribute to the stability of tertiary structures.

L-cystine is a white crystalline powder, insoluble in water and water, the disulfide is easily soluble in alkaline lye and mineral acids.

Cystine is contained up to 17 % in the keratin and is connected there via disulfide bridges.

Thus, keratin (from hair, bristles or feathers) contains about 11 % peptide-bound L-cystine. There are also kidney stones which consist of L-cystine.

Cystine is mainly produced by fermentation using genetically modified bacteria of the Escherichia coli type.

Furthermore, cystine can be obtained by hydrolysis of keratin-containing proteins (poultry feathers, hair).

L-cystine is widely used in the food industry.

L-cystine as well as various cystine compounds are used in cosmetic formulations.

Dicapryl cystine is a preparation which, like dimethyl cystinate (INCI), is effective as an antistatic agent in hair cosmetics.

L-Cystine (INCI) also has an antistatic effect (reduces static electricity by neutralizing the electrical charge on the surface of skin and hair); it is also used as a hair conditioner (makes hair easy to comb, smooth, soft and shiny and gives it volume).