Functional regulation of brain pyruvate dehydrogenase: Postnatal development, anesthesia and food-deprivation

The activity of brain pyruvate dehydrogenase complex (PDHC), is regulated by reversible phosphorylation of the alpha subunit of the E1 component (pyruvate dehydrogenase, EC 1.2.4.1) of PDHC. Using an in vitro back-titration assay, we have evaluated the postnatal development of E1α phosphorylation, as well as the effects of acute pentobarbital administration and food-deprivation on cerebral cortical E1α phosphorylation in synaptosomal and free mitochondrial compartments of the albino rat. Between birth and postnatal day 25, the back-titration phosphorylation increased ca 4-fold, with the largest increase occurring between days 15 and 20. The phosphorylation of E1α in the synaptosomal, but not free mitochondrial fraction, was decreased during pentobarbital anesthesia. Following 72 h of food-deprivation, E1α phosphorylation was decreased in both subcellular fractions. The postnatal increase in E1α back-titration phosphorylation is consistent with and similar in magnitude to previously reported increases in the specific enzymatic activity of PDHC. These results also highlight the potential importance of localized subcellular alterations in mitochondrial metabolism and further validate the back-titration phosphorylation of E1α as a valuable tool for the study of central nervous system PDHC metabolism.