[3][4] The catalytic activities of this enzyme complex involves a coordination system of enzymatic reactions between the alpha and beta subunits.

More specifically, the FAS catalysis mechanism consumes an acetyl coenzyme A (acetyl-CoA) and seven malonyl-CoA molecules to produce a palmitoyl-CoA.

The crystal structure of yeast fatty acid synthase has also been derived, showing both alpha and beta subunits.

Priming is performed in the β subunit, and is catalyzed by the acetyltransferase (AT, equivalent to bacterial (acyl-carrier-protein) S-acetyltransferase) domain, which initiates the process of fatty acid synthesis.

ACP first delivers the acetate group, which had been attached during priming, to the ketoacyl synthase (KS) domain in the α subunit.

The newly bound malonyl-ACP then swings back to the KS domain and transfers the malonate group for chain elongation.

Now in the KS domain, the bound acyl group is condensed with the malonate to form 3-ketoacyl intermediate: β-ketobutyryl-ACP, releasing carbon dioxide in the process.

Another reduction reaction then performed in the enoyl reductase (ER) domain of the β subunit to form a saturated acyl-ACP chain.

Finally, ACP brings the substrate back to the KS domain of the α subunit for another cycle of elongation.

[7][10] Notice the unique characteristic of ACP, which is vital to fatty acid synthesis in its role of shuttling the reaction intermediates between the α and β subunits’ catalytic domains.

[11] Studies have also found that human fatty acid synthase is overly expressed in prostate cancer cells.