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.
Read more about this topic: Long-chain-fatty-acid—Co A Ligase
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