Palmitoyl-acyl carrier protein thioesterase

Bhore, S.J., Shah, F.H., 2012. Genetic transformation of the American oil palm (Elaeis oleiferd) immature zygotic embryos with antisense Palmitoyl-acyl carrier protein thioesterase (PATE) gene. World Appl. Sci. J. 16 (3), 362-369. 

The thioesterase activity of the fatty acid synthase prefers the palmitoyl acyl carrier protein thioester as substrate. 

Jones, A., Davies, H.M., Voelker, T.A. 1995. Palmitoyl-acyl carrier protein (ACP) thioesterase and the evolutionary origin of plant acyl-ACP thioesterases. Plant Cell 7 359-371. 

Fig. 3. Generic reaction sequence for the FASs. ACP, acyl carrier protein AT, acetyltransferase MT, malonyl transferase KS, P-ketoacyl synthase KR, P-ketoacyl reductase DH, dehydrase ER, enoyl reductase TE, thioesterase FT, palmitoyl transferase. In the animal FAS the acetyl and malonyl loading reactions are catalyzed by the same acyl transferase and the chain-termination reaction is catalyzed by a thioesterase. In the fungal FAS, the malonyl loading and palmitoyl unloading reactions are catalyzed by the same acyl transferase. Stereochemical analyses in the laboratories of Comforth and Hammes established that in both animal and fungal FASs the KS-catalyzed condensation reaction proceeds with inversion of configuration at the malonyl C2 position, followed by KR-catalyzed reduction of the 3-keto moiety to the 3R alcohol by transfer of the pro-4S hydride from NADPH, and DH-catalyzed dehydration to a trans-enoyl moiety by the syn elimination of the 2S hydrogen and the 3/f hydroxyl as water. However, the stereochemistry of the final reduction reaction catalyzed by ER domain proceeds with different stereochemistry. The animal FAS transfers the pro-4R hydride of NADPH to the pro-3/f position with simultaneous addition of a solvent proton to the pro-2S position, whereas the fungal FAS takes the pro-4S hydride of NADPH into the pro-3S position and the solvent proton is incorporated at the pro-25 position.

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