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外観
白色の結晶性粉末
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定義
本品は、次の化学式で表されるアミノ酸である。
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溶解性
水に溶けやすく、エタノールにほとんど溶けない。
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解説
スレオニン，トレオニンともいい、α(アルファ)-アミノ酸の一つ。略号はThrまたはT。分子内に2個の不斉炭素原子をもつので四つの立体異性体（L、D、L-アロ、D-アロ）がある。天然にあるのはL型である。1935年ローズWilliam Cumming Rose（1887―1985）らによりフィブリンの酸加水分解物から単離された。L-スレオニンはタンパク質を構成するアミノ酸の一つで、全卵タンパク質の5.3％、乳タンパク質の4％を占める。またカゼインなどのタンパク質中にリン酸エステルの形でも存在する。スレオニンとN-アセチル-D-ガラクトサミンの間のO-グリコシド結合は糖鎖（グルコースやガラクトースなどの糖が鎖状に連なった物質）がタンパク質に結合する様式の一つである。スレオニンのヒドロキシ基のリン酸化はタンパク質のリン酸化の様式の一つである。酵母、細菌では、アスパラギン酸からホモセリンを経るか、グリシンにスレオニンアルドラーゼが働いて合成され、代謝されて、グリシン、α-ケトブチル酸、2-アミノアセト酢酸などになる。分子量119.12。水によく溶け、アルコール、エーテルには溶けない。
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化粧品の成分用途
ヘアコンディショニング剤、皮膚コンディショニング剤
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説明
Threonine (abbreviated as Thr or T) is an α-amino acid with the chemical formula HO2CCH(NH2)CH(OH)CH3. Its codons are ACU, ACA, ACC, and ACG. This essential amino acid is classified as polar. Together with serine, threonine is one of two proteinogenic amino acids bearing an alcohol group (tyrosine is not an alcohol but a phenol, since its hydroxyl group is bonded directly to an aromatic ring, giving it different acid/base and oxidative properties). It is also one of two common amino acids that bear a chiral side chain, along with isoleucine.
The threonine residue is susceptible to numerous posttr anslational modifications. The hydroxy side-chain can undergo Olinked glycosylation. In addition, threonine residues undergo phospho rylation through the action of a threonine kinase. In its phosphorylated form, it can be referred to as phospho threonine.
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化学的特性
White crystalline powder
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天然物の起源
Foods high in threonine include cottage cheese, poultry, fish, meat, lentils, Black turtle bean and Sesame seeds.
Racemic threonine can be prepared from crotonic acid by alphafunctionalization using mercury (II) acetate.
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来歴
Threonine was discovered as the last of the 20 common proteinogenic amino acids in the 1930s by William Cumming Rose.
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使用
DL-Threonine is used as a polar essential amino acid. It serves as a precursor of glycine as well as used in the biosynthesis of proteins. Further, it is used for biochemical research. In addition to this, it is used as a nutrition enhancer.
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生合成
As an essential amino acid, threonine is not synthesized in humans, hence we must ingest threonine in the form of threoninecontaining proteins. In plants and microorganisms, threonine is synthesized from aspartic acid via α-aspartyl-semialdehyde and homoserine. Homoserine undergoes O-phosphorylation; this phosphate ester undergoes hydrolysis concomitant with relocation of the OH group. Enzymes involved in a typical biosynthesis of threonine include :
aspartokinase
β-aspartate semialdehyde dehydrogenase
homoserine dehydrogenase
homoserine kinase
threonine synthase.
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代謝
Threonine is metabolized in two ways:
It is converted to pyruvate via threonine dehydrogenase. An intermediate in this pathway can undergo thiolysis with CoA to produce acetyl-CoA and glycine.
In humans, it is converted to α-ketobutyrate in a less common pathway via the enzyme serine dehydratase, and thereby enters the pathway leading to succinyl-CoA.
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