Mechanism
Thioesters are more reactive than oxygen esters and are common intermediates in fatty-acid metabolism. These thioesters are made by conjugating the fatty acid with the free SH group of the pantetheine moiety of either coenzyme A (CoA) or acyl carrier protein (ACP).
All thiolases, whether they are biosynthetic or degradative in vivo, preferentially catalyze the degradation of 3-ketoacyl-CoA to form acetyl-CoA and a shortened acyl-CoA species, but are also capable of catalyzing the reverse Claisen condensation reaction. It is well established from studies on the biosynthetic thiolase from Z. ramigera that the thiolase reaction occurs in two steps and follows ping-pong kinetics. In the first step of both the degradative and biosynthetic reactions, the nucleophilic Cys89 (or its equivalent) attacks the acyl-CoA (or 3-ketoacyl-CoA) substrate,leading to the formation of a covalent acyl-CoA intermediate. In the second step, the addition of CoA (in the degradative reaction) or acetyl-CoA (in the biosynthetic reaction) to the acyl–enzyme intermediate triggers the release of the product from the enzyme.
Read more about this topic: Thiolase
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