The inactivation of pyruvate dehydrogenase by fatty acid in isolated rat liver mitochondria.

The influence of fatty acid on the interconversion of the pyruvate dehydrogenase complex (PDH) between its active (dephospho-) and inactive (phospho-) forms and on the intramitochondrial $\text{ATP}\text{ADP}$, $\text{NADH}\text{NAD}{}^{\mathrm{+}}$ and $\text{acetyl-CoA}\text{CoASH}$ ratios was studied in isolated rat liver mitochondria. Conditions were found in which the PDH activity was inversely correlated only with the $\text{NADH}\text{NAD}{}^{\mathrm{+}}$ ratio. Under other conditions the PDH activity was inversely correlated solely with the $\text{acetyl-CoA}\text{CoASH}$ ratio. These experiments suggest that the activity of the regulatory enzymes involved in the inactivation and reactivation of the pyruvate dehydrogenase multienzyme complex may be controlled by both the intramitochondrial $\text{NADH}\text{NAD}{}^{\mathrm{+}}$ and $\text{acetyl-CoA}\text{CoASH}$ ratios.