Examples of Enolate Oxyanion Holes

The active site of enoyl-CoA isomerase is a good example of an active site built on the framework of the crotonase fold. It is now weU established that this crotonase fold provides an active site framework that has been used by Nature for a wide range of different chemical reactions, as reviewed recently [73, 85]. The reaction of this enoyl-CoA isomerase is initiated by a catalytic base, Glul36, abstracting a proton from the Ca-carbon, generating the negatively charged enolate 

Citrate synthase catalyzes the aldol reaction between acetyl-CoA and oxaloace-tate. The acyl-CoA Hnk is then cleaved by hydrolysis, releasing a molecule of citrate and free CoA. 

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