Cysteine in the Pharmaceutical Industry
In the pharmaceutical sector, the primary use of L-cysteine is as starter material for the production of the cysteine derivatives N-acetyl-L-cysteine and S-(carboxymethyl)-L-cysteine. Both derivatives serve therapeutic uses as mucolytics. The SH groups are formed in vivo in the case of S-(carboxymethyl)-L-cysteine. They destroy the disulfide bridges of proteinsin bronchial phlegm and lower its viscosity.
Of late, N-acetyl-L-cysteine is also being used as a nutraceutical, especially on the U.S. market. As L-cysteine raises the glutathione level, it boosts redox activity, especially in the liver.
L-cysteine also serves as a processing auxiliary for refolding genetically engineered protein active molecules, e.g. in the production of human insulin. This application, too, is based on the capability of the SH-groups to break incorrectly formed disulfide bridges – but in this case to form them correctly again subsequently.
Moreover, L-cysteine is used in the pharma industry as a building block for protein and peptide actives. The customers are companies that produce amino acids that are protected at first, and are subsequently used in peptide synthesis.
In medical diagnostics, cysteine functions as a component of nutrients, e.g. agar plates and nutrient broths used for cultivating bacteria.