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V. De novo Synthesis of Fatty Acids

Overview Overview: Tissue locations Overview: Reaction sum     Enzymes and Isolated Reactions Enzymes and Isolated Reactions: Acetyl CoA carboxylase Enzymes and Isolated Reactions: Activities of FA Synthase Enzymes and Isolated Reactions: Characteristics of Fatty Acyl Synthase     Acetyl Groups and Reducing Equivalents     Previous Page Next Page

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+ + 6 H2O

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

Glucose Yields Acetyl CoA -- Schematic

This process is somewhat roundabout.

  1. Glucose is first degraded to pyruvate by aerobic glycolysis in the cytoplasm.
  2. Pyruvate is then transported into the mitochondria, where pyruvate dehydrogenase oxidatively decarboxylates pyruvate, forming acetyl CoA and other products.
  3. Acetyl CoA can then serve as a substrate for citrate synthesis.
  4. 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.


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