L-Cysteine
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L-Cysteine

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L-Cysteine is a non-essential amino acid that can be synthesized by the human body under normal physiological conditions if a sufficient quantity of methionine is available. L-Cysteine is commonly used as a precursor in the food and pharmaceutical industries. L-Cysteine is used as a processing aid for baking, as an additive in cigarettes, as well as in the preparation of meat flavours.

Category
L-Amino Acids
Catalog number
BAT-008087
CAS number
52-90-4
Molecular Formula
C3H7NO2S
Molecular Weight
121.16
L-Cysteine
IUPAC Name
(2R)-2-amino-3-sulfanylpropanoic acid
Synonyms
Cysteine, L-; (R)-2-Amino-3-mercaptopropanoic acid; (R)-2-Amino-3-sulfanylpropanoic acid; (R)-Cysteine; L-(+)-Cysteine; L-Alanine, 3-mercapto-; L-Cys; Cystein; Cysteine; E 920; Half-cystine; NSC 8746; Propanoic acid, 2-amino-3-mercapto-, (R)-; Thioserine; β-Mercaptoalanine
Related CAS
4371-52-2 (Deleted CAS) 154605-72-8 (Deleted CAS) 1404190-35-7 (Deleted CAS)
Appearance
White crystalline powder
Purity
≥95%
Density
1.6666 g/cm3
Melting Point
240°C (dec.)
Boiling Point
293.9±35.0°C at 760 mmHg
Storage
Store at RT
Solubility
Soluble in Aqueous Acid, Water
InChI
InChI=1S/C3H7NO2S/c4-2(1-7)3(5)6/h2,7H,1,4H2,(H,5,6)/t2-/m0/s1
InChI Key
XUJNEKJLAYXESH-REOHCLBHSA-N
Canonical SMILES
C(C(C(=O)O)N)S

L-Cysteine is a naturally occurring, sulfur-containing amino acid that plays a crucial role in various biological processes. It is a non-essential amino acid, which means that the human body can synthesize it under normal physiological conditions. However, it can also be obtained from dietary sources, such as poultry, eggs, dairy products, and certain plant-based foods. The molecular structure of L-Cysteine includes a thiol group, which is responsible for its characteristic reactivity and ability to form disulfide bonds, pivotal in protein structure stabilization. L-Cysteine is often used in its hydrochloride form, known as L-Cysteine HCl, which enhances its solubility and stability, making it more accessible for commercial and therapeutic purposes.

One of the primary applications of L-Cysteine is in the food industry, where it serves as a dough conditioner in bakery products. By breaking down gluten, it improves the elasticity and workability of the dough, which leads to enhanced texture and volume of the final baked goods. Moreover, L-Cysteine is utilized as a flavor enhancer, particularly in the production of savory flavors that replicate the taste of poultry and meat. It also plays a role in the Maillard reaction, a chemical reaction between amino acids and reducing sugars, which gives browned foods their distinctive flavor profile.

In the pharmaceutical industry, L-Cysteine is valued for its mucolytic properties, making it effective in treating conditions involving excessive mucus production. It acts by breaking down the disulfide bonds in mucus, thereby reducing its viscosity and facilitating easier expulsion from the respiratory tract. This therapeutic application is especially beneficial for patients with chronic obstructive pulmonary disease (COPD) and cystic fibrosis. Additionally, L-Cysteine is used as a precursor in the synthesis of glutathione, a critical antioxidant in the body, thus playing a role in managing oxidative stress-related conditions.

The cosmetic industry also harnesses the benefits of L-Cysteine, primarily for its ability to strengthen hair and improve skin health. It is a key component in hair care products, where it helps to repair and strengthen hair shafts by promoting the formation of keratin, a structural protein in hair. In skincare, L-Cysteine’s antioxidant properties help to protect the skin from damage caused by environmental pollutants and ultraviolet (UV) radiation. By combating oxidative stress, it aids in maintaining youthful and healthy skin appearance.

Lastly, L-Cysteine finds application in the biotechnology sector, particularly in cell culture and fermentation processes. It serves as a growth supplement in culture media, providing essential nutrients that promote the growth and maintenance of microbial and mammalian cells. In fermentation technology, L-Cysteine can be utilized to enhance the production yield of specific biochemicals and proteins. Its role in maintaining the redox balance in microbial cultures underscores its importance in optimizing and scaling up biotechnological production processes.

1.Shifting redox states of the iron center partitions CDO between crosslink formation or cysteine oxidation.
Njeri CW;Ellis HR Arch Biochem Biophys. 2014 Sep 15;558:61-9. doi: 10.1016/j.abb.2014.06.001. Epub 2014 Jun 11.
Cysteine dioxygenase (CDO) is a mononuclear iron-dependent enzyme that catalyzes the oxidation of L-cysteine to L-cysteine sulfinic acid. The mammalian CDO enzymes contain a thioether crosslink between Cys93 and Tyr157, and purified recombinant CDO exists as a mixture of the crosslinked and non crosslinked isoforms. The current study presents a method of expressing homogenously non crosslinked CDO using a cell permeative metal chelator in order to provide a comprehensive investigation of the non crosslinked and crosslinked isoforms. Electron paramagnetic resonance analysis of purified non crosslinked CDO revealed that the iron was in the EPR silent Fe(II) form. Activity of non crosslinked CDO monitoring dioxygen utilization showed a distinct lag phase, which correlated with crosslink formation. Generation of homogenously crosslinked CDO resulted in an ∼5-fold higher kcat/Km value compared to the enzyme with a heterogenous mixture of crosslinked and non crosslinked CDO isoforms.
2.Lysine- and cysteine-based protein adductions derived from toxic metabolites of 8-epidiosbulbin E acetate.
Lin D;Wang K;Guo X;Gao H;Peng Y;Zheng J Toxicol Lett. 2016 Dec 15;264:20-28. doi: 10.1016/j.toxlet.2016.10.007. Epub 2016 Nov 2.
Furanoid 8-epidiosbulbin E acetate (EEA) is a major constituent of herbal medicine Dioscorea bulbifera L. (DB), a traditional herbal medicine widely used in Asian nations. Our early studies demonstrated that administration of EEA caused acute hepatotoxicity in mice and the observed toxicity required P450-mediated metabolic activation. Protein modification by reactive metabolites of EEA has been suggested to be an important mechanism of EEA-induced hepatotoxicity. The objectives of the present study were to investigate the interaction of the electrophilic reactive metabolites derived from EEA with lysine and cysteine residues of proteins and to define the correlation of protein adductions of EEA and the hepatotoxicity induced by EEA. EEA-derived cis-enedial was found to modify both lysine and cysteine residues of proteins. The observed modifications increased with the increase in doses administered in the animals. The formation of protein adductions derived from the reactive metabolites of EEA were potentiated by buthionine sulfoximine, but were attenuated by ketoconazole.
3.Electron transfer pathways in a light, oxygen, voltage (LOV) protein devoid of the photoactive cysteine.
Kopka B;Magerl K;Savitsky A;Davari MD;Röllen K;Bocola M;Dick B;Schwaneberg U;Jaeger KE;Krauss U Sci Rep. 2017 Oct 17;7(1):13346. doi: 10.1038/s41598-017-13420-1.
Blue-light absorption by the flavin chromophore in light, oxygen, voltage (LOV) photoreceptors triggers photochemical reactions that lead to the formation of a flavin-cysteine adduct. While it has long been assumed that adduct formation is essential for signaling, it was recently shown that LOV photoreceptor variants devoid of the photoactive cysteine can elicit a functional response and that flavin photoreduction to the neutral semiquinone radical is sufficient for signal transduction. Currently, the mechanistic basis of the underlying electron- (eT) and proton-transfer (pT) reactions is not well understood. We here reengineered pT into the naturally not photoreducible iLOV protein, a fluorescent reporter protein derived from the Arabidopsis thaliana phototropin-2 LOV2 domain. A single amino-acid substitution (Q489D) enabled efficient photoreduction, suggesting that an eT pathway is naturally present in the protein. By using a combination of site-directed mutagenesis, steady-state UV/Vis, transient absorption and electron paramagnetic resonance spectroscopy, we investigate the underlying eT and pT reactions.
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