WordNet

being or containing a hydroxyl group

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/12/28 15:58:53」(JST)

wiki en

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

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

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

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

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

References

^ 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.

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 副腎ステロイドの代謝 metabolism of adrenal steroids
2. 副腎ステロイド生合成 adrenal steroid biosynthesis
3. 幼児および小児における低カルシウム血症の病因 etiology of hypocalcemia in infants and children
4. Causes of vitamin D deficiency and resistance
5. 多嚢胞性卵巣症候群におけるステロイドホルモン代謝 steroid hormone metabolism in polycystic ovary syndrome

English Journal

Transformation and toxicity assessment of two UV filters using UV/H2O2 process.

Peng M1, Du E2, Li Z1, Li D1, Li H1.
The Science of the total environment.Sci Total Environ.2017 Dec 15;603-604:361-369. doi: 10.1016/j.scitotenv.2017.06.059. Epub 2017 Jun 23.
PMID 28633113

Detection and characterization of the metabolites of rutaecarpine in rats based on ultra-high-performance liquid chromatography with linear ion trap-Orbitrap mass spectrometer.

Cai W1, Guan Y1, Zhou Y1, Wang Y1, Ji H1, Liu Z1.
Pharmaceutical biology.Pharm Biol.2017 Dec;55(1):294-298.
PMID 27927077

Environmental behavior of 12 UV filters and photocatalytic profile of ethyl-4-aminobenzoate.

Li AJ1, Sang Z2, Chow CH2, Law JC2, Guo Y3, Leung KS4.
Journal of hazardous materials.J Hazard Mater.2017 Sep 5;337:115-125. doi: 10.1016/j.jhazmat.2017.04.067. Epub 2017 Apr 28.
PMID 28511043

Japanese Journal

Pilot-scale whole-cell biocatalysis for the hydroxylation of cyclosporine derivative, FR901459, at higher concentrations by Lentzea sp. 7887 using soybean flour as a novel substrate dispersant