Question

Discuss about fatty acid synthase – multienzyme complex and its regulatory role
Evaluation criteria
o Able to introduce fatty acid synthase effectively through a concise and
clear summary
o Able to list the multienzyme complex involved in fatty acid synthase
o Able to discuss the role of fatty acid synthase regulatory
o Proper references

Answer 1

Fatty acid synthase or FAS is a multi enzyme complex that catalyses the fatty acid synthesis. It includes all the polypeptides or proteins or enzymes required for the conversion of acetyl and malonyl CoAs to the corresponding ACPs and the cleavage of bound ACP to release complete fatty acid chains by enzymes termed thioesterases.

Fatty acid synthase consists of a homodimer of two identical subunits. 3 catalytic domains towards the N- terminal ,of ketoacyl synthase (KS), malonyl/ acetyltransferase (MAT) and dehdrase (DH) are separated by a region of 600 residuesfrom the C-terminal domains which consists of thioesterase, acyl carrier protein, ketoacyl reductase and enoyl reductase.  

The production and metabolic activity of fatty acid synthase is subject to transcriptional regulation by Upstream Stimulatory Cofactors (namely USF1 and USF2) and sterol regulatory element binding protein - 1x (SREBP - 1c) in response to feeding/ insulin levels in animals. Regulation of FAS by SREBP - 1c is USF - dependent.