| 翻訳と辞書 |
Kinase
In biochemistry, a kinase is an enzyme that catalyzes the transfer of phosphate groups from high-energy, phosphate-donating molecules to specific substrates. This process is known as phosphorylation, where the substrate gains a phosphate group and the high-energy ATP molecule donates a phosphate group. This transesterification produces a phosphorylated substrate and ADP. Conversely, it is referred to as dephosphorylation when the phosphorylated substrate donates a phosphate group and ADP gains a phosphate group (producing a dephosphorylated substrate and the high energy molecule of ATP). These two processes, phosphorylation and dephosphorylation, occur four times during glycolysis.〔 TheFreeDictionary.com〕〔(【引用サイトリンク】title=History of ATP research milestones from an ATP-related chemistry )〕 Kinases are part of the larger family of phosphotransferases. Kinases are not to be confused with phosphorylases, which catalyze the addition of inorganic phosphate groups to an acceptor, nor with phosphatases, which remove phosphate groups. The phosphorylation state of a molecule, whether it be a protein, lipid, or carbohydrate, can affect its activity, reactivity, and its ability to bind other molecules. Therefore, kinases are critical in metabolism, cell signalling, protein regulation, cellular transport, secretory processes, and many other cellular pathways.
==Biochemistry and functional relevance==
Kinases mediate the transfer of a phosphate moiety from a high energy molecule (such as ATP) to their substrate molecule, as seen in the figure below. Kinases are needed to stabilize this reaction because the phosphoanhydride bond contains a high level of energy. Kinases properly orient their substrate and the phosphoryl group within their active sites, which increases the rate of the reaction. Additionally, they commonly use positively charged amino acid residues, which electrostatically stabilize the transition state by interacting with the negatively charged phosphate groups. Alternatively, some kinases utilize bound metal cofactors in their active sites to coordinate the phosphate groups.
Kinases are used extensively to transmit signals and regulate complex processes in cells. Phosphorylation of molecules can enhance or inhibit their activity and modulate their ability to interact with other molecules. The addition and removal of phosphoryl groups provides the cell with a means of control because various kinases can respond to different conditions or signals. Mutations in kinases that lead to a loss-of-function or gain-of-function can cause cancer and disease in humans, including certain types of leukemia and neuroblastomas, glioblastoma, spinocerebellar ataxia (type 14), forms of agammaglobulinaemia, and many others.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
■ウィキペディアで「Kinase」の詳細全文を読む
スポンサード リンク
| 翻訳と辞書 : 翻訳のためのインターネットリソース |
Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.
|
|