So we have a second coenzyme A molecule that comes into the reaction and it uses its thyl group to actually cleave the bond between the second, the alpha carbon and the third carbon, the beta carbon. And because it's the thyl group of the coenzyme A that is acting as a nucleophile and cleaving that bond this cleavage is known as a Thiolytic cleavage of bico enzyme A. Now, the enzyme that catalyzes the final step of this process is the beta keto thylase enzyme. So in the final step, beta keto thylase catalyzes the cleavage of the sigma bond between the second carbon and the third carbon. And so in this particular reaction, the molecule that is the nucleophile is another coenzyme A. So the coenzyme A acts as a nuclear file and uses a thyl group to basically carry out this thylytic cleavage reaction.