Hormones regulate acetyl-CoA carboxylase by a separate mechanism – phosphorylation (inactive form) and dephosphorylation (active form) of the enzyme. Glucagon, epinephrine, and norepinephrine inactivate the enzyme by cAMP-dependent phosphorylation. Insulin, on the other hand, dephosphorylates and activates the enzyme. Thus, insulin promotes fatty acid synthesis while glucagons inhibits. Insulin stimulates tissues’ uptake of glucose and conversion of pyruvate to acetyl-CoA. This also facilitates fatty acid formation.