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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/12/12 15:01:57」(JST)

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Hydroxylation is a chemical process that introduces a hydroxyl group (-OH) into an organic compound. In biochemistry, hydroxylation reactions are often facilitated by enzymes called hydroxylases. Hydroxylation is the first step in the oxidative degradation of organic compounds in air. It is extremely important in detoxification since hydroxylation converts lipophilic compounds into water-soluble (hydrophilic) products that are more readily excreted. Some drugs (e.g. steroids) are activated or deactivated by hydroxylation.

Chemical concepts[edit]

The hydroxylation process involves conversion of a CH group into a COH group. Hydroxylation is an oxidative process. The oxygen that is inserted into the C-H bond is usually derived from atmospheric oxygen (O2). Since O2 itself is a slow hydroxylating agent, catalysts are required to accelerate the pace of the process.

Biological hydroxylation[edit]

The principal hydroxylation agent in nature is cytochrome P-450, hundreds of variations of which are known. Other hydroxylating agents include flavins.^[1]

Hydroxylation of proteins[edit]

The principal residue to be hydroxylated in proteins is proline. The hydroxylation occurs at the γ-C atom, forming hydroxyproline (Hyp), an essential element of collagen, in turn a necessary element of connective tissue. Proline hydroxylation is also a vital component of hypoxia response via hypoxia inducible factors. In some cases, proline may be hydroxylated instead on its β-C atom. Lysine may also be hydroxylated on its δ-C atom, forming hydroxylysine (Hyl).

These three reactions are catalyzed by very large, multi-subunit enzymes prolyl 4-hydroxylase, prolyl 3-hydroxylase and lysyl 5-hydroxylase, respectively. These reactions require iron (as well as molecular oxygen and α-ketoglutarate) to carry out the oxidation, and use ascorbic acid (vitamin C) to return the iron to its oxidized state. Deprivation of ascorbate leads to deficiencies in proline hydroxylation, which leads to less stable collagen, which can manifest itself as the disease scurvy. Since citrus fruits are rich in vitamin C, British sailors were given limes to combat scurvy on long ocean voyages; hence, they were called "limeys".

Examples of hydroxylases[edit]

17α-Hydroxylase
Cholesterol 7 alpha-hydroxylase
Dopamine β-hydroxylase
Phenylalanine hydroxylase
Tyrosine hydroxylase

References[edit]

^ Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISBN 1-57259-153-6.

This protein-related article is a stub. You can help Wikipedia by expanding it.

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1. 11βヒドロキシラーゼ欠損症による先天性副腎過形成 congenital adrenal hyperplasia due to 11 beta hydroxylase deficiency
2. ビタミンDの代謝 metabolism of vitamin d
3. 21－ヒドロキシラーゼ欠損症による非古典的（遅発性）先天性副腎皮質過形成の診断
および治療 diagnosis and treatment of nonclassic late onset congenital adrenal hyperplasia due to 21 hydroxylase deficiency
4. 先天性副腎過形成の稀な原因 uncommon causes of congenital adrenal hyperplasia
5. 成人における21－ヒドロキシラーゼ欠損症による古典的な先天性副腎皮質過形成の治療 treatment of classic congenital adrenal hyperplasia due to 21 hydroxylase deficiency in adults

English Journal

The simultaneous presence of neuroepithelial cells and neuroepithelial bodies in the respiratory gas bladder of the longnose gar, Lepisosteus osseus, and the spotted gar, L. oculatus.

Zaccone D, Dabrowski K, Lauriano ER, de Pasquale A, Macrì D, Satora L, Lanteri G.SourceDepartment of Animal Biology and Marine Ecology, Faculty of Science, University of Messina, Italy. zacconed@unime.it
Acta histochemica.Acta Histochem.2012 Jul;114(4):370-8. Epub 2011 Aug 9.
Anatomical and functional studies on the autonomic innervation as well as the location of airway receptors in the air-bladder of lepisosteids are very fragmentary. These water-breathing fishes share in common with the bichirs the presence of a glottis (not a ductus pneumaticus) opening into the esop
PMID 21831413

Characterization and neural differentiation of mouse embryonic and induced pluripotent stem cells on cadherin-based substrata.

Haque A, Yue XS, Motazedian A, Tagawa Y, Akaike T.SourceDepartment of Biomolecular Engineering, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan.
Biomaterials.Biomaterials.2012 Jul;33(20):5094-106. Epub 2012 Apr 19.
A suitable culture condition using advanced biomaterials has the potential to improve stem cell differentiation into selective lineages. In this study, we evaluated the effects of recombinant extracellular matrix (ECM) components on the mouse embryonic stem (mES) and induced pluripotent stem (miPS)
PMID 22520296

Japanese Journal

Cloning of the Flavonoid 3'-Hydroxylase Gene of Eustoma grandiflorum (Raf.) Shinn. (EgF3'H) and Complementation of an F3'H-deficient Mutant of Ipomoea nil (L.) Roth. by Heterologous Expression of EgF3'H

Takatori Yuka,Shimizu Keiichi,Ogata Jun [他]
The horticulture journal 84(2), 131-139, 2015-04
NAID 40020428810

Ethyl 3,4-dihydroxy benzoate, a unique preconditioning agent for alleviating hypoxia-mediated oxidative damage in L6 myoblasts cells

Nimker Charu,Kaur Gurpreet,Revo Anshula [他]
The journal of physiological sciences 65(1), 77-87, 2015-01
NAID 40020323585

新規去勢抵抗性前立腺癌治療薬アビラテロン酢酸エステル（ザイティガ®錠250 mg）の薬理学的特徴および臨床試験成績

岩田理子,堤健一郎,原田寧
日本薬理学雑誌 145(5), 260-265, 2015
… アビラテロン酢酸エステルは生体内で速やかにアビラテロンへ加水分解され，アンドロゲン合成酵素であるC17,20-lyase/17α-hydroxylase（CYP17）を阻害する．アビラテロンは精巣，副腎および腫瘍組織内におけるアンドロゲン合成を阻害することにより，去勢抵抗性前立腺癌（CRPC）に対して抗腫瘍効果を示す．アビラテロンはヒト精巣由来CYP17を不可逆的に阻害し，ヒト副腎皮質腫瘍細胞株を用いたin vitroでの検討およびマウス …
NAID 130005067369

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★リンクテーブル★

リンク元	「水酸化酵素」「プロリン水酸化酵素」「ヒドロキシラーゼ」「mixed function oxygenase」
拡張検索	「cholesterol 7alpha-hydroxylase」「benzoate 4-hydroxylase」「21-hydroxylase deficiency」「21-hydroxylase欠損症」