L-システイン

解説天然のR(L)形は分解点178 ℃．[α]25D－16.5°(水)．pK1 1.71，pK2 8.33，pK3 10.78．水，エタノール，氷酢酸，アンモニア水に易溶，ほかの有機溶媒に難溶．微量の金属の存在下ではとくに不安定で，空気酸化されてシスチンにかわる．解毒剤や食用補剤に用いられる．LD50 1890 mg/kg(ラット，経口)．森北出版「化学辞典（第2版）

用途化粧品、食品の添加物、酸化防止剤

用途SH 基を有する化合物です。 粘液ムコタンパクのジスルフィド結合を解離 する作用を示します。

用途SH 基を有する化合物です。 粘液ムコタンパクのジスルフィド結合を解離 する作用を示します。

説明Cysteine (abbreviated as Cys or C) is an α-amino acid with the chemical formula HO2CCH(NH2)CH2SH. It is a semi - essential amino acid, which means that it can be biosynthesized in humans. The thiol side chain in cysteine 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. When used as a food additive, it has the E number E920.

天然物の起源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. In contrast, cystine travels safely through the GI tract and blood plasma and is promptly reduced to the two cysteine molecules upon cell entry. Industrial sources The majority of L - cysteine is obtained industrially by hydrolysis of poultry feathers or human hair. Synthetically produced L-cysteine, compliant with Jewish Kosher and Muslim Halal rules, is also available, albeit at a higher price. The synthetic route involves fermentation utilizing a mutant of E. coli. Biosynthesis 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 betasynthase then combines homocysteine and serine to form the asymmetrical thioether cystathionine. The enzyme cystathionine gamma-lyase converts the cystathionine into cysteine and alphaketobutyrate.

使用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. It is used in foods to prevent oxygen from destroying vitamin c and is used in doughs to reduce mixing time.