Hydroxylation 398687 221892397 2008-06-26T15:40:37Z Itub 426390 recat '''Hydroxylation''' is any chemical process that introduces one or more hydroxyl groups (-OH) into a compound (or radical) thereby [[oxidation|oxidizing]] it. In biochemistry, hydroxylation reactions are often facilitated by [[enzyme]]s called hydroxylases. ==Hydroxylation in proteins== The principal residue to be hydroxylated in proteins is [[Proline]]. The hydroxilation occurs at the <math>\mathrm{C^{\gamma}}</math> 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 (medical)|hypoxia]] response via [[hypoxia inducible factor]]s. In some cases, proline may be hydroxylated instead on its <math>\mathrm{C^{\beta}}</math> atom. Lysine may also be hydroxylated on its <math>\mathrm{C^{\delta}}</math> 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 [[sailor]]s were given [[Lime (fruit)|limes]] to combat scurvy on long ocean voyages; hence, they were called "lymies". ==Examples of hydroxylases== * [[17α-hydroxylase]] * [[Cholesterol 7 alpha-hydroxylase]] * [[Phenylalanine hydroxylase]] * [[Tyrosine hydroxylase]] {{Protein posttranslational modification}} [[Category:Organic redox reactions]] [[Category:Proteins]] [[Category:Posttranslational modification]] {{protein-stub}} [[cs:Hydroxylace]] [[de:Hydroxylierung]] [[fr:Hydroxylation]] [[it:Idrossilazione]] [[ja:ヒドロキシル化反応]] [[pl:Hydroksylowanie]] [[sv:Hydroxylering]]