| L-システイン |
|
|
|
|
|
別称
2-Amino-3-mercaptopropanoic acid
|
| 識別情報 |
| CAS登録番号 |
52-90-4 ,
52-89-1 (塩酸塩) |
| PubChem |
5862 |
| ChemSpider |
574 (ラセミ体) , 5653 (L-体) |
| UNII |
K848JZ4886 |
| EINECS番号 |
200-158-2 |
| KEGG |
C00097 |
| ChEMBL |
CHEMBL54943 |
- C([C@@H](C(=O)O)N)S
C(C(C(=O)O)N)S
|
- InChI=1S/C3H7NO2S/c4-2(1-7)3(5)6/h2,7H,1,4H2,(H,5,6)
Key: XUJNEKJLAYXESH-UHFFFAOYSA-N
InChI=1/C3H7NO2S/c4-2(1-7)3(5)6/h2,7H,1,4H2,(H,5,6)/t2-/m0/s1
Key: XUJNEKJLAYXESH-REOHCLBHBU
InChI=1/C3H7NO2S/c4-2(1-7)3(5)6/h2,7H,1,4H2,(H,5,6)
Key: XUJNEKJLAYXESH-UHFFFAOYAC
|
| 特性[1] |
| 化学式 |
C3H7NO2S |
| モル質量 |
121.16 g mol−1 |
| 外観 |
白色結晶または粉末 |
| 融点 |
240 °C（分解）
|
| 水への溶解度 |
可溶 |
| 比旋光度 [α]D |
+9.4º (H2O, c = 1.3) |
| 特記なき場合、データは常温 (25 °C)・常圧 (100 kPa) におけるものである。 |
システイン (cysteine) はアミノ酸の1つで、2-アミノ-3-スルファニルプロピオン酸のこと。側鎖にメルカプト基を持つ。チオセリンとも言う。略号は C あるいは Cys。酸性条件下では安定だが、中・アルカリ性条件では微量の重金属イオンにより容易に空気酸化されシスチンとなる。酸化型のシスチンと対比し、還元型であることを明らかにするために CySH と記されることもある。
目次
- 1 性質
- 2 存在
- 3 生化学
- 4 利用
- 5 羊
- 6 生合成
- 7 出典
- 8 関連項目
- 9 外部リンク
性質
親水性アミノ酸、中性極性側鎖アミノ酸に分類される。含硫アミノ酸。蛋白質構成アミノ酸のひとつで、非必須アミノ酸。糖原性を持つ。
存在
少量ではあるが大部分の蛋白質にみられる。食物では、赤唐辛子、ニンニク、タマネギ、ブロッコリー、芽キャベツ、オート麦、小麦胚芽に含まれる。体内ではメチオニンから作り出される。
生化学
求核性が非常に高いメルカプト基を持つため求核性触媒として働く。システインのメルカプト基のpKaは約 8 だが、その反応性は環境・条件によって調節される。システインを求核剤として含むタンパク質にユビキチンリガーゼがあり、これはユビキチンを結合するタンパク質に移動させる。カスパーゼはアポトーシスの際のタンパク質分解に関与する。インテインはシステイン触媒の補助によって作用することがある。これらの働きは、通常システインが酸化されない細胞内環境に限定される。
システインはタンパク質を分子間で架橋させることができる。これにより、細胞外の厳しい環境での分子の安定性が向上し、タンパク質分解に対する抵抗性が与えられる（タンパク質の排泄にはコストがかかるので、その必要性は最小限に抑える方が有利である）。細胞内において、ポリペプチド中のシステイン間のジスルフィド結合はタンパク質の三次構造を維持する。インスリンはシステイン架橋されたペプチドの代表例であり、2つの独立したペプチド鎖が1組のジスルフィド結合によってつながれている。毛髪においては、システインによるジスルフィド結合の配列が巻き毛の度合いを決める。
ジスルフィド結合の生成はタンパク質ジスルフィド異性化酵素によって触媒される。細胞内でデヒドロアスコルビン酸が小胞体へと輸送され、酸化的な環境を作り出す。ここでシステインはシスチンに酸化され、求核剤としての作用を失う。
システインの誘導体である N-アセチル-L-システイン (NAC)（N-acetylcysteine）は一般的なサプリメントであり、抗酸化剤のグルタチオンへと代謝される。システインの名はシスチンから付けられたが、これはギリシャ語で膀胱を意味する kustis に由来する。シスチンは腎臓結石から最初に単離された。
利用
主として自然に存在する L-システインの形で、食物、医薬品、パーソナルケア製品に用いられる。最も主要な用途は香料の製造である。例えばメイラード反応で糖と反応させると肉の香りを持つ成分が生成する。また、パンを焼くときの添加剤としても使われる。少量（約 10 ppm 程度）を加えることによって生地がやわらかくなり、製造にかかる時間が短縮される。
パーソナルケアの分野では、主にアジアでパーマネントウエーブに用いられる。システインは髪のケラチンのジスルフィド結合を切断する。
生体分子の構造・動態を研究する際に行われる部位特異的標識実験の対象としても一般的である。マレイミドはマイケル付加によって選択的にシステインと結合する。電子スピン共鳴での部位特異的スピン標識にも用いられる。
誘導体の N-アセチルシステイン (NAC) （N-acetylcysteine）はしばしば鎮咳剤として用いられる。これは、粘液中のジスルフィド結合を切断して液状化させ、痰を切れやすくするためである。既に述べたようにサプリメントとしても使われる。
タバコ製造業の上位5社の1994年の報告によると、システインは紙巻タバコへの599の添加物のうちの1つである。他の添加物と同様、添加の目的は明らかにされていない。
羊
羊にとって、システインは羊毛を作り出すのに必要だが、体内で作り出せない必須アミノ酸なので食草から摂取しなければならない。このため、羊は乾季には羊毛の生産を止める。しかしながら遺伝子組み換えによってシステインを自ら作り出せる羊が開発されている。
生合成
生体内では、メチオニンの硫黄原子がセリンのヒドロキシ基酸素原子と置き換わることにより、シスタチオニンを経由して合成される。
メチオニンがメチオニンアデノシルトランスフェラーゼ (EC 2.5.1.6)、メチルトランスフェラーゼ (EC 2.1.1.-)、アデノシルホモシステイナーゼ (EC 3.3.1.1) によりホモシステイン (homocysteine) となり、これがシスタチオニン-β-シンターゼ (EC 4.2.1.22) によりセリンと結合してシスタチオニン (cystathionine) を経てシスタチオニン-γ-リアーゼ (EC 4.4.1.1) によりシステインとなる。
出典
- ^ Weast, Robert C., ed. (1981), CRC Handbook of Chemistry and Physics (62nd ed.), Boca Raton, FL: CRC Press, p. C-259, ISBN 0-8493-0462-8 .
関連項目
外部リンク
- システイン - 「健康食品」の安全性・有効性情報 （国立健康・栄養研究所）
|
タンパク質を構成するアミノ酸 |
| 主なトピック |
|
|
| 特性 |
| 脂肪族 |
- 分枝鎖アミノ酸 (バリン
- イソロイシン
- ロイシン)
- メチオニン
- アラニン
- プロリン
- グリシン
|
| 芳香族 |
- フェニルアラニン
- チロシン
- トリプトファン
- ヒスチジン
|
| 極性なし |
|
| 正電荷 (pKa) |
- リシン (≈10.8)
- アルギニン (≈12.5)
- ヒスチジン (≈6.1)
|
| 負電荷 (pKa) |
- アスパラギン酸 (≈3.9)
- グルタミン酸 (≈4.1)
- システイン (≈8.3)
- チロシン (≈10.1)
|
|
| 分類 |
- 必須アミノ酸
- ケト原性アミノ酸
- 糖原性アミノ酸
- タンパク質を構成しないアミノ酸（英語版）
|
- 主要な生体物質
- 炭水化物
- アルコール
- 糖タンパク質
- 配糖体
- 脂質
- エイコサノイド
- 脂肪酸/脂肪酸の代謝中間体
- リン脂質
- スフィンゴ脂質
- ステロイド
- 核酸
- 核酸塩基
- ヌクレオチド代謝中間体
- タンパク質
- タンパク質を構成するアミノ酸/アミノ酸の代謝中間体
- テトラピロール
- ヘムの代謝中間体
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Not to be confused with cytosine, cystine, cytisine, cytidine, or Sistine.
"Cys" redirects here. For other uses, see Cys (disambiguation).
L-Cysteine
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|
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| Names |
| IUPAC name
Cysteine
|
| Other names
2-Amino-3-sulfhydrylpropanoic acid
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| Identifiers |
|
CAS Number
|
52-90-4 Y
52-89-1 (hydrochloride) N |
| ChEBI |
CHEBI:15356 Y |
| ChEMBL |
ChEMBL54943 Y |
| ChemSpider |
574 (Racemic) Y
5653 (L-form) Y |
| EC Number |
200-158-2 |
|
IUPHAR/BPS
|
4782 |
| Jmol 3D model |
Interactive image
Interactive image |
| KEGG |
D00026 Y |
| PubChem |
5862 |
| UNII |
K848JZ4886 Y |
InChI
-
InChI=1S/C3H7NO2S/c4-2(1-7)3(5)6/h2,7H,1,4H2,(H,5,6) Y
Key: XUJNEKJLAYXESH-UHFFFAOYSA-N Y
-
InChI=1/C3H7NO2S/c4-2(1-7)3(5)6/h2,7H,1,4H2,(H,5,6)/t2-/m0/s1
Key: XUJNEKJLAYXESH-REOHCLBHBU
-
InChI=1/C3H7NO2S/c4-2(1-7)3(5)6/h2,7H,1,4H2,(H,5,6)
Key: XUJNEKJLAYXESH-UHFFFAOYAC
|
SMILES
-
C([C@@H](C(=O)O)N)S
-
C(C(C(=O)O)N)S
|
| Properties[2] |
|
Chemical formula
|
C3H7NO2S |
| Molar mass |
121.15 g·mol−1 |
| Appearance |
white crystals or powder |
| Melting point |
240 °C (464 °F; 513 K) decomposes |
|
Solubility in water
|
soluble |
| Solubility |
1.5g/100g ethanol 19 degC [1] |
|
Chiral rotation ([α]D)
|
+9.4° (H2O, c = 1.3) |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|
| N verify (what is YN ?) |
| Infobox references |
|
|
Cysteine (abbreviated as Cys or C)[3] is a semi-essential[4] proteinogenic amino acid with the formula HO2CCH(NH2)CH2SH. It is encoded by the codons UGU and UGC. The thiol side chain in cysteine often participates in enzymatic reactions, as a nucleophile. The thiol is susceptible to oxidization to give the disulfide derivative cystine, which serves an important structural role in many proteins. When used as a food additive, it has the E number E920.
Contents
- 1 Sources
- 1.1 Dietary sources
- 1.2 Industrial sources
- 1.3 Biosynthesis
- 2 Biological functions
- 2.1 Precursor to the antioxidant glutathione
- 2.2 Precursor to iron-sulfur clusters
- 2.3 Metal ion binding
- 2.4 Roles in protein structure
- 3 Applications
- 3.1 Reducing toxic effects of alcohol
- 3.2 N-Acetylcysteine
- 4 Sheep
- 5 Dietary Restrictions
- 6 See also
- 7 References
- 8 External links
Sources
Dietary sources
Although classified as a non-essential amino acid, in rare cases, cysteine may be essential for infants, the elderly, and individuals with certain metabolic disease or who suffer from malabsorption syndromes. Cysteine can usually be synthesized by the human body under normal physiological conditions if a sufficient quantity of methionine is available. Cysteine is catabolized in the gastrointestinal tract and blood plasma[citation needed]. In contrast, cystine travels safely through the GI tract and blood plasma and is promptly reduced to the two cysteine molecules upon cell entry.[citation needed]
Cysteine is found in most high-protein foods, including:
- Animal sources: meat (including pork and poultry), eggs, dairy;[5]
- Plant sources: red peppers, garlic, onions, broccoli, brussels sprout, oats, granola, wheat germ, sprouted lentils.[6][unreliable source?]
Like other amino acids, cysteine has an amphoteric character.
(
R)-Cysteine (left) and (
S)-Cysteine (right) in zwitterionic form at neutral pH
Industrial sources
The majority of L-cysteine is obtained industrially by hydrolysis of animal materials, such as poultry feathers or hog hair. Despite widespread belief otherwise, there is little evidence that human hair is used as a source material and its use is explicitly banned in the European Union.[7] Synthetically produced L-cysteine, compliant with Jewish kosher and Muslim halal laws, is also available, albeit at a higher price.[8] The synthetic route involves fermentation using a mutant of E. coli. Degussa introduced a route from substituted thiazolines.[9] Following this technology, L-cysteine is produced by the hydrolysis of racemic 2-amino-Δ2-thiazoline-4-carboxylic acid using Pseudomonas thiazolinophilum.[10]
Biosynthesis
Cysteine synthesis. Cystathionine beta synthase catalyzes the upper reaction and cystathionine gamma-lyase catalyzes the lower reaction.
In animals, biosynthesis begins with the amino acid serine. The sulfur is derived from methionine, which is converted to homocysteine through the intermediate S-adenosylmethionine. Cystathionine beta-synthase then combines homocysteine and serine to form the asymmetrical thioether cystathionine. The enzyme cystathionine gamma-lyase converts the cystathionine into cysteine and alpha-ketobutyrate. In plants and bacteria, cysteine biosynthesis also starts from serine, which is converted to O-acetylserine by the enzyme serine transacetylase. The enzyme O-acetylserine (thiol)-lyase, using sulfide sources, converts this ester into cysteine, releasing acetate.[11]
Biological functions
The cysteine thiol group is nucleophilic and easily oxidized. The reactivity is enhanced when the thiol is ionized, and cysteine residues in proteins have pKa values close to neutrality, so are often in their reactive thiolate form in the cell.[12] Because of its high reactivity, the thiol group of cysteine has numerous biological functions.
Precursor to the antioxidant glutathione
Due to the ability of thiols to undergo redox reactions, cysteine has antioxidant properties. Cysteine's antioxidant properties are typically expressed in the tripeptide glutathione, which occurs in humans as well as other organisms. The systemic availability of oral glutathione (GSH) is negligible; so it must be biosynthesized from its constituent amino acids, cysteine, glycine, and glutamic acid. Glutamic acid and glycine are readily available in most Western diets, but the availability of cysteine can be the limiting substrate.[citation needed]
Precursor to iron-sulfur clusters
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.[13]
Metal ion binding
Beyond the iron-sulfur proteins, many other metal cofactors in enzymes are bound to the thiolate substituent of cysteinyl residues. Examples include zinc in zinc fingers and alcohol dehydrogenase, copper in the blue copper proteins, iron in cytochrome P450, and nickel in the [NiFe]-hydrogenases.[14] The thiol group also has a high affinity for heavy metals, so that proteins containing cysteine, such as metallothionein, will bind metals such as mercury, lead, and cadmium tightly.[15]
Roles in protein structure
In the translation of messenger RNA molecules to produce polypeptides, cysteine is coded for by the UGU and UGC codons.
Cysteine has traditionally been considered to be a hydrophilic amino acid, based largely on the chemical parallel between its thiol group and the hydroxyl groups in the side-chains of other polar amino acids. However, the cysteine side chain has been shown to stabilize hydrophobic interactions in micelles to a greater degree than the side chain in the non-polar amino acid glycine, and the polar amino acid serine.[16] In a statistical analysis of the frequency with which amino acids appear in different chemical environments in the structures of proteins, free cysteine residues were found to associate with hydrophobic regions of proteins. Their hydrophobic tendency was equivalent to that of known non-polar amino acids such as methionine and tyrosine (tyrosine is polar aromatic but also hydrophobic[17]), and was much greater than that of known polar amino acids such as serine and threonine.[18] Hydrophobicity scales, which rank amino acids from most hydrophobic to most hydrophilic, consistently place cysteine towards the hydrophobic end of the spectrum, even when they are based on methods that are not influenced by the tendency of cysteines to form disulfide bonds in proteins. Therefore, cysteine is now often grouped among the hydrophobic amino acids,[19][20] though it is sometimes also classified as slightly polar,[21] or polar.[4]
While free cysteine residues do occur in proteins, most are covalently bonded to other cysteine residues to form disulfide bonds. Disulfide bonds play an important role in the folding and stability of some proteins, usually proteins secreted to the extracellular medium.[22] Since most cellular compartments are reducing environments, disulfide bonds are generally unstable in the cytosol with some exceptions as noted below.
Figure 2: Cystine (shown here in its neutral form), two cysteines bound together by a disulfide bond.
Disulfide bonds in proteins are formed by oxidation of the thiol groups of cysteine residues. The other sulfur-containing amino acid, methionine, cannot form disulfide bonds. 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 rigidity of proteins 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 tertiary structure. Insulin is an example of a protein with cystine crosslinking, wherein two separate peptide chains are connected by a pair of disulfide bonds.
Protein disulfide isomerases catalyze the proper formation of disulfide bonds; the cell transfers dehydroascorbic acid to the endoplasmic reticulum, which oxidises the environment. In this environment, cysteines are, in general, oxidized to cystine and are no longer functional as a nucleophiles.
Aside from its oxidation to cystine, cysteine participates in numerous posttranslational modifications. The nucleophilic thiol group allows cysteine to conjugate to other groups, e.g., in prenylation. Ubiquitin ligases transfer ubiquitin to its pendant, proteins, and caspases, which engage in proteolysis in the apoptotic cycle. Inteins often function with the help of a catalytic cysteine. These roles are typically limited to the intracellular milieu, where the environment is reducing, and cysteine is not oxidized to cystine.
Applications
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.[23] L-Cysteine is also used as a processing aid for baking.[24]
In the field of personal care, cysteine is used for permanent wave applications, predominantly in Asia. Again, the cysteine is used for breaking up the disulfide bonds in the hair's keratin.
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.
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.[25] Its inclusion in cigarettes could offer two benefits: acting as an expectorant, since smoking increases mucus production in the lungs; or increasing the beneficial antioxidant glutathione (which is diminished in smokers).
Reducing toxic effects of alcohol
Cysteine has been proposed as a preventative or antidote for some of the negative effects of alcohol, including liver damage and hangover. It counteracts the poisonous effects of acetaldehyde. Cysteine supports the next step in metabolism, which turns acetaldehyde into the relatively harmless acetic acid. In a rat study, test animals received an LD50 dose of acetaldehyde. Those that received cysteine had an 80% survival rate; when both cysteine and thiamine were administered, all animals survived.[26] No direct evidence indicates its effectiveness in humans who consume alcohol at low levels.
N-Acetylcysteine
N-Acetyl-L-cysteine is a derivative of cysteine wherein an acetyl group is attached to the nitrogen atom. This compound is sold as a dietary supplement, and used as an antidote in cases of acetaminophen overdose,[27] and obsessive compulsive disorders such as trichotillomania.
Sheep
Cysteine is required by sheep to produce wool: It is an essential amino acid that must be taken in from their feed. As a consequence, during drought conditions, sheep produce less wool; however, transgenic sheep that can make their own cysteine have been developed.[28]
Dietary Restrictions
The presence of L-Cysteine is often a point of contention for people following dietary restrictions such as Kosher, Halal, Vegan or Vegetarian as it may be sourced from various human or animal sources.[29] As a result, an increasing amount of L-Cysteine is produced via a microbial or other synthetic processes.
See also
|
Wikimedia Commons has media related to Cysteine. |
- Amino acids
- Cysteine metabolism
- Cystinuria
- Selenocysteine
- Thiols
- Sullivan reaction
References
- ^ Belitz, H.-D; Grosch, Werner; Schieberle, Peter (2009-02-27). Food Chemistry. ISBN 9783540699330
- ^ Weast, Robert C., ed. (1981). CRC Handbook of Chemistry and Physics (62nd ed.). Boca Raton, FL: CRC Press. p. C-259. ISBN 0-8493-0462-8. .
- ^ "Nomenclature and symbolism for amino acids and peptides (IUPAC-IUB Recommendations 1983)", Pure Appl. Chem., 56 (5): 595–624, 1984, doi:10.1351/pac198456050595
- ^ a b "The primary structure of proteins is the amino acid sequence". The Microbial World. University of Wisconsin-Madison Bacteriology Department. Retrieved 16 September 2012.
- ^ "Cysteine". University of Maryland Medical Center.
- ^ "Lentils, sprouted, raw". bitterpoison.com.
- ^ "EU Chemical Requirements". http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2012:083:0001:0295:EN:PDF.
- ^ "Questions About Food Ingredients: What is L-cysteine/cysteine/cystine?". Vegetarian Resource Group.
- ^ Martens, Jürgen; Offermanns, Heribert; Scherberich, Paul (1981). "Facile Synthesis of Racemic Cysteine". Angewandte Chemie International Edition in English. 20 (8): 668. doi:10.1002/anie.198106681.
- ^ Drauz, Karlheinz; Grayson, Ian; Kleemann, Axel; Krimmer, Hans-Peter; Leuchtenberger, Wolfgang; Weckbecker, Christoph (2007). "Amino Acids". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a02_057.pub2. ISBN 3-527-30673-0.
- ^ Hell R (1997). "Molecular physiology of plant sulfur metabolism". Planta. 202 (2): 138–48. doi:10.1007/s004250050112. PMID 9202491.
- ^ Bulaj G, Kortemme T, Goldenberg DP (June 1998). "Ionization-reactivity relationships for cysteine thiols in polypeptides". Biochemistry. 37 (25): 8965–72. doi:10.1021/bi973101r. PMID 9636038.
- ^ Lill R, Mühlenhoff U (2006). "Iron-sulfur protein biogenesis in eukaryotes: components and mechanisms". Annu. Rev. Cell Dev. Biol. 22: 457–86. doi:10.1146/annurev.cellbio.22.010305.104538. PMID 16824008.
- ^ Lippard, Stephen J.; Berg, Jeremy M. (1994). Principles of Bioinorganic Chemistry. Mill Valley, CA: University Science Books. ISBN 0-935702-73-3. [page needed]
- ^ Baker DH, Czarnecki-Maulden GL (June 1987). "Pharmacologic role of cysteine in ameliorating or exacerbating mineral toxicities". J. Nutr. 117 (6): 1003–10. PMID 3298579.
- ^ Heitmann P (January 1968). "A model for sulfhydryl groups in proteins. Hydrophobic interactions of the cystein side chain in micelles". Eur. J. Biochem. 3 (3): 346–50. doi:10.1111/j.1432-1033.1968.tb19535.x. PMID 5650851.
- ^ "A Review of Amino Acids (tutorial)". Curtin University.
- ^ Nagano N, Ota M, Nishikawa K (September 1999). "Strong hydrophobic nature of cysteine residues in proteins". FEBS Lett. 458 (1): 69–71. doi:10.1016/S0014-5793(99)01122-9. PMID 10518936.
- ^ Betts, M.J.; R.B. Russell (2003). "Hydrophobic amino acids". Amino Acid Properties and Consequences of Substitutions, In: Bioinformatics for Geneticists. Wiley. Retrieved 2012-09-16.
- ^ Gorga, Frank R. (1998–2001). "Introduction to Protein Structure--Non-Polar Amino Acids". Retrieved 2012-09-16.
- ^ "Virtual Chembook--Amino Acid Structure". Elmhurst College. Retrieved 2012-09-16.
- ^ Sevier CS, Kaiser CA (November 2002). "Formation and transfer of disulphide bonds in living cells". Nat. Rev. Mol. Cell Biol. 3 (11): 836–47. doi:10.1038/nrm954. PMID 12415301.
- ^ Huang, Tzou-Chi; Ho, Chi-Tang. Hui, Y. H.; Nip, Wai-Kit; Rogers, Robert, eds. "Meat Science and Applications, ch. Flavors of Meat Products". CRC: 71–102. ISBN 978-0-203-90808-2.
- ^ "Food Ingredients and Colors". U.S. Food and Drug Administration. November 2004. Retrieved 2009-09-06 .[dead link]
- ^ Martin, Terry (2009-06-25). "The List of Additives in Cigarettes". about.com. Retrieved 2009-09-06. .
- ^ Sprince H, Parker CM, Smith GG, Gonzales LJ (April 1974). "Protection against acetaldehyde toxicity in the rat by L-cysteine, thiamin and L-2-methylthiazolidine-4-carboxylic acid". Agents Actions. 4 (2): 125–30. doi:10.1007/BF01966822. PMID 4842541.
- ^ Kanter MZ (October 2006). "Comparison of oral and i.v. acetylcysteine in the treatment of acetaminophen poisoning". Am J Health Syst Pharm. 63 (19): 1821–7. doi:10.2146/ajhp060050. PMID 16990628.
- ^ Powell BC, Walker SK, Bawden CS, Sivaprasad AV, Rogers GE (1994). "Transgenic sheep and wool growth: possibilities and current status". Reprod. Fertil. Dev. 6 (5): 615–23. doi:10.1071/RD9940615. PMID 7569041.
- ^ "Kosher View of L-Cysteine". kashrut.com. May 2003.
External links
- Cysteine MS Spectrum
- International Kidney Stone Institute
- http://www.chemie.fu-berlin.de/chemistry/bio/aminoacid/cystein en.html
- Nagano N, Ota M, Nishikawa K (September 1999). "Strong hydrophobic nature of cysteine residues in proteins". FEBS Lett. 458 (1): 69–71. doi:10.1016/S0014-5793(99)01122-9. PMID 10518936.
- 952-10-3056-9 Interaction of alcohol and smoking in the pathogenesis of upper digestive tract cancers - possible chemoprevention with cysteine
- Cystine Kidney Stones
- Kosher View of L-Cysteine
|
Cough and cold preparations (R05)
|
|
| Expectorants |
- Althea root
- Antimony pentasulfide
- Creosote
- Guaiacolsulfonate
- Guaifenesin (+ oxomemazine)
- Ipecacuanha (Syrup of ipecac)
- Levoverbenone
- Potassium iodide
- Senega
- Tyloxapol
- Ammonium Chloride
|
|
| Mucolytics |
- Acetylcysteine
- Ambroxol
- Bromhexine
- Carbocisteine
- Domiodol
- Dornase alfa
- Eprazinone
- Erdosteine
- Letosteine
- Mannitol
- Mesna
- Neltenexine
- Sobrerol
- Stepronin
- Tiopronin
|
|
| Cough suppressants |
Opium alkaloids,
opioids,
and derivatives |
- Acetyldihydrocodeine
- Benzylmorphine
- Butorphanol
- Codeine
- Dextromethorphan
- Dihydrocodeine
- Dimemorfan
- Droxypropine
- Ethylmorphine
- Heroin
- Hydrocodone
- Hydromorphone
- Isoaminile
- Laudanum
- Levomethadone
- Levopropoxyphene
- Methadone
- Nicocodeine
- Nicodicodeine
- Normethadone
- Noscapine
- Pholcodine
- Thebacon
- Tipepidine
|
|
| Other |
- Benzonatate
- Benproperine
- Bibenzonium bromide
- Butamirate
- Clobutinol
- Clofedanol
- Cloperastine
- Diphenhydramine
- Dibunate
- Dimethoxanate
- Dropropizine
- Fedrilate
- Glaucine
- Levodropropizine
- Meprotixol
- Morclofone
- Nepinalone
- Oxolamine
- Oxeladin
- Pentoxyverine
- Pipazetate
- Prenoxdiazine
- Piperidione
- Zipeprol
|
|
|
Antidotes (V03AB)
|
|
Nervous
system |
Nerve agent /
Organophosphate
poisoning |
- Atropine#
- Biperiden
- Diazepam#
- Oximes
- see also: Cholinesterase
|
|
|
Barbiturate
overdose
|
|
|
|
Benzodiazepine
overdose
|
|
|
|
GHB overdose
|
|
|
|
Opioid overdose
|
- Diprenorphine
- Doxapram
- Nalmefene
- Nalorphine
- Naloxone#
- Naltrexone
|
|
|
Reversal of
neuromuscular blockade
|
|
|
|
Circulatory
system |
|
Beta blocker
|
|
|
|
Digoxin toxicity
|
|
|
|
Heparin
|
|
|
|
| Other |
|
Arsenic poisoning
|
|
|
|
Cyanide poisoning
|
- 4-Dimethylaminophenol
- Hydroxocobalamin
- nitrite
- Amyl nitrite
- Sodium nitrite#
- Sodium thiosulfate#
|
|
|
Hydrofluoric acid
|
|
|
Methanol /
Ethylene glycol
poisoning |
- Primary alcohols: Ethanol
- Fomepizole
|
|
|
Paracetamol toxicity
(Acetaminophen)
|
- Acetylcysteine#
- Glutathione
- Methionine#
|
|
|
|
- Dimercaprol#
- Edetates
- Prussian blue#
|
|
|
Other
|
- iodine-131
- Methylthioninium chloride#
- oxidizing agent
- Prednisolone/promethazine
|
|
|
| Emetic |
- Copper sulfate
- Ipecacuanha
|
|
- #WHO-EM
- ‡Withdrawn from market
- Clinical trials:
- †Phase III
- §Never to phase III
|
|
The encoded amino acid
|
|
| General topics |
- Protein
- Peptide
- Genetic code
|
|
|
| By properties |
|
Aliphatic
|
- Branched-chain amino acids (Valine
- Isoleucine
- Leucine)
- Methionine
- Alanine
- Proline
- Glycine
|
|
|
Aromatic
|
- Phenylalanine
- Tyrosine
- Tryptophan
- Histidine
|
|
|
Polar, uncharged
|
- Asparagine
- Glutamine
- Serine
- Threonine
|
|
|
Positive charge (pKa)
|
- Lysine (≈10.8)
- Arginine (≈12.5)
- Histidine (≈6.1)
|
|
|
Negative charge (pKa)
|
- Aspartic acid (≈3.9)
- Glutamic acid (≈4.1)
- Cysteine (≈8.3)
- Tyrosine (≈10.1)
|
|
|
| Other classifications |
- Essential amino acid
- Ketogenic amino acid
- Glucogenic amino acid
- Non-proteinogenic amino acid
|
|
E numbers
|
|
- Colours (E100–199)
- Preservatives (E200–299)
- Antioxidants & acidity regulators (E300–399)
- Thickeners, stabilisers & emulsifiers (E400–499)
- pH regulators & anticaking agents (E500–599)
- Flavour enhancers (E600–699)
- Miscellaneous (E900–999)
- Additional chemicals (E1100–1599)
- Waxes (E900–909)
- Synthetic glazes (E910–919)
- Improving agents (E920–929)
- Packaging gases (E930–949)
- Sweeteners (E950–969)
- Foaming agents (E990–999)
- L-cysteine (E920)
- L-cystine (E921)
- Potassium persulfate (E922)
- Ammonium persulfate (E923)
- Potassium bromate (E924)
- Chlorine (E925)
- Chlorine dioxide (E926)
- Azodicarbonamide (E927)
- Carbamide (E927b)
- Benzoyl peroxide (E928)
|
|
Amino acid metabolism metabolic intermediates
|
|
| K→acetyl-CoA |
|
lysine→
|
- Saccharopine
- Allysine
- α-Aminoadipic acid
- α-Ketoadipate
- Glutaryl-CoA
- Glutaconyl-CoA
- Crotonyl-CoA
- β-Hydroxybutyryl-CoA
|
|
|
leucine→
|
- α-Ketoisocaproic acid
- β-hydroxy β-methylbutyric acid
- β-hydroxy β-methylbutyryl-CoA
- Isovaleryl-CoA
- 3-Methylcrotonyl-CoA
- 3-Methylglutaconyl-CoA
- HMG-CoA
|
|
|
tryptophan→alanine→
|
- N'-Formylkynurenine
- Kynurenine
- Anthranilic acid
- 3-Hydroxykynurenine
- 3-Hydroxyanthranilic acid
- 2-Amino-3-carboxymuconic semialdehyde
- 2-Aminomuconic semialdehyde
- 2-Aminomuconic acid
- Glutaryl-CoA
|
|
|
| G |
|
G→pyruvate→citrate
|
|
glycine→serine→
|
- glycine→creatine: Glycocyamine
- Phosphocreatine
- Creatinine
|
|
|
|
G→glutamate→
α-ketoglutarate
|
|
histidine→
|
- Urocanic acid
- Imidazol-4-one-5-propionic acid
- Formiminoglutamic acid
- Glutamate-1-semialdehyde
|
|
|
proline→
|
- 1-Pyrroline-5-carboxylic acid
|
|
|
arginine→
|
- Agmatine
- Ornithine
- Citrulline
- Cadaverine
- Putrescine
|
|
|
other
|
- cysteine+glutamate→glutathione: γ-Glutamylcysteine
|
|
|
|
G→propionyl-CoA→
succinyl-CoA
|
|
valine→
|
- α-Ketoisovaleric acid
- Isobutyryl-CoA
- Methacrylyl-CoA
- 3-Hydroxyisobutyryl-CoA
- 3-Hydroxyisobutyric acid
- 2-Methyl-3-oxopropanoic acid
|
|
|
isoleucine→
|
- 2,3-Dihydroxy-3-methylpentanoic acid
- 2-Methylbutyryl-CoA
- Tiglyl-CoA
- 2-Methylacetoacetyl-CoA
|
|
|
methionine→
|
- generation of homocysteine: S-Adenosyl methionine
- S-Adenosyl-L-homocysteine
- Homocysteine
- conversion to cysteine: Cystathionine
- alpha-Ketobutyric acid+Cysteine
|
|
|
threonine→
|
|
|
|
propionyl-CoA→
|
|
|
|
|
G→fumarate
|
|
phenylalanine→tyrosine→
|
- 4-Hydroxyphenylpyruvic acid
- Homogentisic acid
- 4-Maleylacetoacetic acid
|
|
|
|
G→oxaloacetate
|
|
|
|
| Other |
|
