The second step is a hydration reaction. But ultimately, we form the citrate molecule from the oxyloacetate and this acetyl coenzyme a. Now, once we form the citrate molecule, it must be transformed into its isomer molecule known as isocitrate. Why? Well, because only the isocitrate can actually undergo the decarboxylation step that takes place in step three. So, in step two, we have an isomerization reaction that is catalyzed by a connotase.