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CASE FILES: BIOCHEMISTRY
Figure 36-3. Mobilization of fatty acids during times in which the liver is syn-
thesizing glucose via the gluconeogenic pathway. The P-oxidation of fatty
acids by the liver produces the energy needed for gluconeogenesis, but
because the TCA cycle is slowed because of depletion of C4 acids (used for
glucose synthesis), ketone bodies (acetoacetate and P-hydroxybutyrate) are
formed from acetyl-CoA to regenerate CoA for continued P-oxidation. The
ketone bodies are exported to extrahepatic tissues, where they are used as an
energy source.
are activated by fatty acid thiokinases producing fatty acid-CoA and requiring
ATP, as shown in Figure 36-4. The fatty acids are transported across the mito-
chondrial inner membrane as carnitine derivatives utilizing the carnitine shut-
tle. All the rest of the reactions occur in the mitochondrial matrix beginning
with the oxidation of the fatty acid by flavin adenine dinucleotide (FAD)-
linked fatty acyl-CoA dehydrogenase producing
trans-A2-enoyl-CoA.
This
product is hydrated by enoylhydratase producing L-3-hydroxyacyl-CoA. This
product undergoes a second oxidation catalyzed by NAD-linked L-3-hydroxy
fatty acyl-CoA dehydrogenase producing 3-ketoacyl-CoA. This product is
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