V. De novo Synthesis of Fatty Acids
Overview: Reaction sum
Sum of the reactions:
8 acetyl CoA + 7 ATP + 14 (NADPH + H+) -> palmitate
(16:0) + 8 CoA + 7 (ADP + Pi) + 14 NADP+ +
This is the overall process for fatty acid synthesis. Acetyl CoA for fatty acid synthesis comes mostly from glycolytic breakdown of glucose.
Glucose Yields Acetyl CoA -- Schematic
This process is somewhat roundabout.
- Glucose is first degraded to pyruvate by aerobic glycolysis in the
- Pyruvate is then transported into the mitochondria, where pyruvate dehydrogenase oxidatively decarboxylates pyruvate, forming acetyl CoA and other
- Acetyl CoA can then serve as a substrate for citrate
- Citrate, in turn, can be transported out of the mitochondria to the cytoplasm (where fatty acid synthesis occurs), and there split to generate cytoplasmic acetyl CoA for fatty acid synthesis.
Citrate can also be oxidized by the tricarboxylic acid cycle in the mitochondria to yield energy. Notice that the need first to form citrate, then to transport it to the cytoplasm and then split it in order to get acetyl CoA for fatty acid synthesis provides several points at which control over acetyl CoA availability can be exerted.