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| 2-enoyl coenzyme A (CoA) hydratase ： ウィキペディア英語版 |
Enoyl-CoA hydratase
Enoyl-CoA hydratase is an enzyme that hydrates the double bond between the second and third carbons on acyl-CoA. This enzyme, also known as crotonase, is essential to metabolizing fatty acids to produce both acetyl CoA and energy.〔Bahnson, Brian J., Vernon E. Anderson, and Gregory A. Petsko. "Structural Mechanism of Enoyl-CoA Hydratase: Three Atoms From a Single Water are Added in Either an E1cb Stepwise or Concerted Fashion." Biochemistry 41 (2002): 2621-2629. SciFinder Scholar. 2 December 2007.〕 Note the crystal structure at right of enoyl-coa hydratase from a rat. The crystal structure shows a hexamer formation (not universal, but human enzyme is also hexameric), which leads to the efficiency of this protein. This enzyme has been discovered to be highly efficient, and allows our bodies to metabolize fatty acids into energy very quickly. In fact this enzyme is so efficient that the rate is equivalent to that of diffusion-controlled reactions.〔TEngel, Christian K., Tiila R. Kiema, J. Kalervo Hiltunen, and Rik K. Wierenga. "The Crystal Structure of Enoyl-CoA Hydratase Complexed with Octanoyl-CoA Reveals the Structural Adaptations Required for Binding of a Long Chain Fatty Acid-CoA Molecule." Journal of Molecular Biology 275 (1998): 847-859. SciFinder Scholar. 2 December 2007.〕
==Biological Significance: Metabolism==
Enoyl-CoA hydratase catalyzes the second step in the breakdown of fatty acids or the second step of β-oxidation in fatty acid metabolism shown below. Fatty acid metabolism is how our bodies turn fats or lipids into energy. When fats come into our bodies, they are generally in the form of triacyl-glycerols. These must be broken down in order for the fats to pass into our bodies. When that happens, three fatty acids are released.
In fatty acid metabolism, fatty acids are changed into fatty acyl-CoA. To do this, the carboxylate which occupies one end of the fatty acid is changed into a thioester by substituting coenzyme A for the hydroxyl group. Next the fatty acyl-CoA is oxidized and broken down into an acetyl-CoA molecule and another acyl-CoA. The acetyl CoA is then sent to the citric acid cycle while the remaining acyl-CoA is broken down further into acetyl-CoAs. The complete breakdown of a fatty acid not only generates acetyl-CoA molecules, but it also generates energy in the form of NADH. This NADH goes on to be converted into ATP which can be used in other reactions.〔Nelson, David L., and Michael M. Cox. Lehninger Principles of Biochemistry. 4th ed. New York: W. H. Freeman and Company, 2005. 637-643.〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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