Record Information
Creation date2010-04-08 22:10:18 UTC
Update date2015-07-20 22:53:02 UTC
Primary IDFDB012679
Secondary Accession NumbersNot Available
Chemical Information
FooDB NameCysteine hydrochloride
DescriptionDietary supplement, nutrient. Dough conditioner Cysteine (abbreviated as Cys or C) is an ?-amino acid with the chemical formula HO2CCH(NH2)CH2SH. It is a non-essential amino acid, which means that it is biosynthesized in humans. Its codons are UGU and UGC. The side chain on cysteine is thiol, which is nonpolar and thus cysteine is usually classified as a hydrophobic amino acid. The thiol side chain often participates in enzymatic reactions, serving as a nucleophile. The thiol is susceptible to oxidization to give the disulfide derivative cystine, which serves an important structural role in many proteins. Cysteine is named after cystine.; Cysteine is a very popular target for site-directed labeling experiments to investigate biomolecular structure and dynamics. Maleimides will selectively attach to cysteine using a covalent Michael addition. Site-directed spin labeling for EPR or paramagnetic relaxation enhanced NMR also uses cysteine extensively.; Cysteine is an important source of sulfide in human metabolism. The sulfide in iron-sulfur clusters and in nitrogenase is extracted from cysteine, which is converted to alanine in the process.; Cysteine is required by sheep in order to produce wool: it is an essential amino acid which must be taken in as food from grass. As a consequence, during drought conditions, sheep stop producing wool; however, transgenic sheep which can make their own cysteine have been developed.[citation needed]; Cysteine, mainly the L-enantiomer, is a precursor in the food, pharmaceutical, and personal care industries. One of the largest applications is the production of flavors. For example, the reaction of cysteine with sugars in a Maillard reaction yields meat flavors. L-cysteine is also used as a processing aid for baking. Small quantities (in the tens of ppm range) help to soften the dough and thus reduce processing time.; High levels of Cysteine, due to its reducing capacity, have been shown to inactivate insulin under certain conditions. This is because insulin contains three disulfide bonds, one of which can be reduced by cysteine. If this happens, insulin looses its characteristic structure and thus looses functionality. During a hypoglycemia attack (where there is too much insulin in the blood causing an unsafe drop in blood sugar) Cysteine can be used to inactivate insulin, allowing blood sugar levels to normalize. In some cases, the use of Thiamine, vitamin C, and Cysteine have been successful in treating severe cases of hypoglycemia. Additionally, due to its interaction with insulin, diabetics should avoid supplements or medications that contain cysteine or have the potential to increase cysteine levels.; In a 1994 report released by five top cigarette companies, cysteine is one of the 599 additives to cigarettes. Like most cigarette additives, however, its use or purpose is unknown. Its inclusion in cigarettes could offer two benefits: Acting as an expectorant, since smoking increases mucus production in the lungs; and increasing the beneficial antioxidant glutathione (which is diminished in smokers).; N-acetyl-L-cysteine (NAC) is a derivative of cysteine wherein an acetyl group is attached to the nitrogen atom. This compound is sometimes considered as a dietary supplement, although it is not an ideal source since it is catabolized in the gut.[citation needed] NAC is often used as a cough medicine because it breaks up the disulfide bonds in the mucus and thus liquefies it, making it easier to cough up. It is also this action of breaking disulfide bonds that makes it useful in thinning the abnormally thick mucus in Cystic Fibrosis patients. NAC is also used as a specific antidote in cases of acetaminophen overdose.; Oxidation of cysteine produces the disulfide cystine. More aggressive oxidants convert cysteine to the corresponding sulfinic acid and sulfonic acid. Cysteine residues play a valuable role by crosslinking proteins, which increases the protein stability in the harsh extracellular environment, and also functions to confer proteolytic resistance (since protein export is a costly process, minimizing its necessity is advantageous). Inside the cell, disulfide bridges between cysteine residues within a polypeptide support the protein's secondary structure. Insulin is an example of a protein with cystine crosslinking, wherein two separate peptide chains are connected by a pair of disulfide bonds.
CAS Number52-89-1
Zinc cysteinateMeSH
L CysteineMeSH
Half cystineMeSH
(r)-cysteine hydrochloridebiospider
3-Mercaptoalanine hydrochloridebiospider
Cystein chloridebiospider
Cysteine chlorhydratebiospider
Cysteine chlorohydratebiospider
Cysteine HCL (anhydrous)biospider
Cysteine hydrochloride (anhydrous)biospider
Cysteine hydrochloride, USANdb_source
Cysteine monohydrochloridebiospider
Cysteine, (l)biospider
Cysteine, hydrochloride, l-biospider
Cysteine, l-, hydrochloridebiospider
Cysteine, l-, monohydrochloridebiospider
L-(+ )-cysteine hydrochloridebiospider
L-(+)-cysteine hydrochloridebiospider
L-2-Amino-3-mercaptopropanoic acid monohydrochloridebiospider
L-cysteine hydrochloridebiospider
L-cysteine hydrochloride anhydrousbiospider
L-cysteine monohydrochloridebiospider
L-cysteine, hydrochloridebiospider
L-Cysteine, hydrochloride (1:1)biospider
Predicted Properties
pKa (Strongest Acidic)2.35ChemAxon
pKa (Strongest Basic)9.05ChemAxon
Physiological Charge0ChemAxon
Hydrogen Acceptor Count3ChemAxon
Hydrogen Donor Count3ChemAxon
Polar Surface Area63.32 ŲChemAxon
Rotatable Bond Count2ChemAxon
Refractivity28.22 m³·mol⁻¹ChemAxon
Polarizability11.46 ųChemAxon
Number of Rings0ChemAxon
Rule of FiveYesChemAxon
Ghose FilterYesChemAxon
Veber's RuleYesChemAxon
MDDR-like RuleYesChemAxon
Chemical FormulaC3H8ClNO2S
IUPAC name2-amino-3-sulfanylpropanoic acid hydrochloride
InChI IdentifierInChI=1S/C3H7NO2S.ClH/c4-2(1-7)3(5)6;/h2,7H,1,4H2,(H,5,6);1H
Isomeric SMILESCl.NC(CS)C(O)=O
Average Molecular Weight157.619
Monoisotopic Molecular Weight156.996426902
DescriptionThis compound belongs to the class of chemical entities known as cysteine and derivatives. These are compounds containing cysteine or a derivative thereof resulting from reaction of cysteine at the amino group or the carboxy group, or from the replacement of any hydrogen of glycine by a heteroatom.
KingdomChemical entities
Super ClassOrganic compounds
ClassOrganic acids and derivatives
Sub ClassCarboxylic acids and derivatives
Direct ParentCysteine and derivatives
Alternative Parents
  • Cysteine or derivatives
  • Alpha-amino acid
  • Amino acid
  • Alkylthiol
  • Carboxylic acid
  • Monocarboxylic acid or derivatives
  • Hydrocarbon derivative
  • Hydrochloride
  • Primary amine
  • Organosulfur compound
  • Organooxygen compound
  • Organonitrogen compound
  • Organic nitrogen compound
  • Primary aliphatic amine
  • Carbonyl group
  • Amine
  • Organic oxygen compound
  • Organopnictogen compound
  • Organic oxide
  • Aliphatic acyclic compound
Molecular FrameworkAliphatic acyclic compounds
External DescriptorsNot Available
Physico-Chemical Properties - Experimental
Physico-Chemical Properties - Experimental
Physical stateNot Available
Physical DescriptionNot Available
Mass CompositionNot Available
Melting PointMp 175-178° dec.DFC
Boiling PointNot Available
Experimental Water SolubilityNot Available
Experimental logPNot Available
Experimental pKaNot Available
Isoelectric pointNot Available
ChargeNot Available
Optical RotationNot Available
Spectroscopic UV DataNot Available
DensityNot Available
Refractive IndexNot Available
SpectraNot Available
ChemSpider IDNot Available
ChEMBL IDNot Available
KEGG Compound IDNot Available
Pubchem Compound ID60960
Pubchem Substance IDNot Available
ChEBI ID52891
Phenol-Explorer IDNot Available
DrugBank IDNot Available
HMDB IDNot Available
CRC / DFC (Dictionary of Food Compounds) IDHJQ86-N:HJQ82-J
Dr. Duke IDNot Available
BIGG IDNot Available
KNApSAcK IDNot Available
HET IDNot Available
Flavornet IDNot Available
GoodScent IDrw1349801
SuperScent IDNot Available
Wikipedia IDCysteine_hydrochloride
Phenol-Explorer Metabolite IDNot Available
Duplicate IDSNot Available
Old DFC IDSNot Available
Associated Foods
FoodContent Range AverageReference
Biological Effects and Interactions
Health Effects / BioactivitiesNot Available
EnzymesNot Available
PathwaysNot Available
MetabolismNot Available
BiosynthesisNot Available
Organoleptic Properties
  1. The Good Scents Company (2009). Flavor and fragrance information catalog. <> Accessed 15.10.23.
MSDSNot Available
Synthesis ReferenceNot Available
General ReferenceNot Available
Content Reference