Number three is it's a rate limiting step? And we'll come back to this step when we'll look at step number four. Now, once we form the Malno Co enzyme A molecule, let's put it aside for a moment and let's look at step number one. Now, the enzyme that catalyzes steps one through step seven is fatty acid syntax. And remember that fatty acid synthase or simply SAS is a single polypeptide chain that actually contains seven different catalytic sites, seven different catalytic domains, as well as an ACP domain. And the ACP domain stands for Acyl carrier protein.