Abstract
Addition of L-glutamate or several citric acid cycle intermediates stimulated the phosphorylation of a protein with apparent molecular weight of 43,000 ( P43 ) in P2-fractions from rat cerebral cortex, and this phosphorylation was inhibited by dichloroacetic acid, a specific inhibitor of pyruvate dehydrogenase kinase. Comparison of several molecular properties of phosphorylated P43 and the phosphorylated alpha-subunit of pyruvate dehydrogenase indicated that both proteins are extracted by a similar procedure and have an identical apparent molecular weight and isoelectric point. Furthermore, digestion of both phosphorylated proteins by several different proteases in the presence of SDS yielded a similar pattern of phosphorylated peptides indicating that these proteins have a considerable sequence homology. Thus, various pieces of evidence indicate that P43 and the alpha-chain of pyruvate dehydrogenase are very similar if not identical. The possible implication of a glutamate stimulated phosphorylation of pyruvate dehydrogenase for long term potentiation and epilepsy is discussed.
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