|
The Long chain fatty acyl-CoA synthetase enzyme is a member of the ligase family that activates the breakdown of complex fatty acids. Long chain fatty acyl-CoA synthetase plays a crucial role in intermediary metabolism by catalyzing the formation of fatty acyl-CoA by a two-step process proceeding through an adenylated intermediate. It is an enzyme present in all organisms from bacteria to humans. It catalyzes the pre-step reaction for β-oxidation of fatty acids or can be incorporated in phospholipids. Long chain fatty acyl-CoA synthetase, LC-FACS, plays a role in the physiological regulation of various cellular functions via the production of long chain fatty acyl-CoA esters, which reportedly have affected protein transport, enzyme activation, protein acylation, cell signaling, and transcriptional regulation.〔 The formation of fatty acyl-CoA is catalyzed in two steps: a stable intermediate of fatty acyl-AMP molecule and then the product is formed—fatty acid acyl-CoA molecule. Fatty acyl CoA synthetase catalyzes the activation of a long fatty acid chain to a fatty acyl CoA, requiring the energy of 1 ATP to AMP and pyrophosphate. This step uses 2 "ATP equivalents" because pyrophosphate is cleaved into 2 molecules of inorganic phosphate, breaking a high-energy phosphate bond. == Mechanism and active site == The mechanism for Long Chain Fatty Acyl-CoA Synthetase is a “bi uni uni bi ping-pong” mechanism.〔 The uni and bi prefixes refer to the number of substrates that enter the enzyme and the number of products that leave the enzyme; bi describes a situation where two substrates enter the enzyme at the same time. Ping-pong signifies that a product is released before another substrate can bind to the enzyme. In step one, ATP and a long chain fatty acid enter the enzyme’s active site. Within the active site the negatively charged oxygen on the fatty acid attacks the alpha phosphate on ATP, forming an ATP-long chain fatty acid intermediate. (Step 1, Figure 3) In the second step, Pyrophosphate (PPi) leaves, resulting in an AMP-long chain fatty acid molecule within the enzyme’s active site. (Step 2, Figure 3) Coenzyme A now enters the enzyme and another intermediate is formed which consists of AMP-long chain fatty acid-Coenzyme A. (Step 3, Figure 3) At the end of this mechanism two products are released, AMP and acyl coa synthetase. (Step 4, Figure 3) Acyl CoA is formed from long chain fatty acids through an acyl substitution. In an ATP dependent reaction, the fatty acid carboxylate is converted to a thioester. The final products of this reaction are acyl-CoA, pyrophosphate (PPi) and AMP. 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「Long-chain-fatty-acid—CoA ligase」の詳細全文を読む スポンサード リンク
|