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Figure 6 Fatty-acid biosynthesis. Cytoplasmic acetyl-CoA (AcCoA) is the primary substrate for de novo fatty-acid synthesis. This two-carbon compound most commonly derives from the glycolytic degradation of glucose, and its formation is dependent upon several reactions in the mitochondria. The mitochondrial enzyme pyruvate carboxylase is found primarily in tissues that can synthesize fatty acids. AcCoA is converted to malonyl-CoA (MalCoA) by acetyl-CoA carboxylase. Using AcCoA as a primer, the fatty-acid synthase multienzyme complex carries out a series of reactions that elongate the growing fatty acid by two carbon atoms. In this process MalCoA condenses with AcCoA, yielding an enzyme-bound four-carbon ,3-ketoacid that is reduced, dehydrated, and reduced again. The product is enzyme-bound 4:0. This process is repeated six more times, after which 16:0 is released from the complex. The reductive steps require NADPH, which is derived from enzyme reactions and pathways shown in grey. Enz refers to the fatty acid synthase multienzyme complex.

1. Glycolysis

2. Pyruvate dehydrogenase

3. Pyruvate carboxylase

4. Citrate synthase

5. ATP citrate lyase

6. Acetyl-CoA carboxylase

7. Fatty-acid synthase multienzyme complex

8. Pentose phosphate pathway

9. Malate dehydrogenase 10. Malic enzyme

Malate

1. Glycolysis

2. Pyruvate dehydrogenase

3. Pyruvate carboxylase

4. Citrate synthase

5. ATP citrate lyase

6. Acetyl-CoA carboxylase

7. Fatty-acid synthase multienzyme complex

8. Pentose phosphate pathway

9. Malate dehydrogenase 10. Malic enzyme

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