The pyruvate dehydrogenase complex is subject to allosteric control, especially inhibition by reaction products. The main regulatory process controlling pyruvate dehydrogenase's activity in eukaryotes is

phosphorylation by ATP and dephosphorylation, which turn off/on the complex

Explanation:

The pyruvate dehydrogenase complex consists of three different enzymes capable of converting pyruvate into acetyl-CoA. The enzymes that form the pyruvate dehydrogenase complex are pyruvate dehydrogenase (E1), dihydrolipoyl transacetylase (E2) and dihydrolipoyl dehydrogenase (E3). In eukaryotic organisms, the pyruvate dehydrogenase complex is controlled by pyruvate dehydrogenase kinase and pyruvate dehydrogenase phosphatase, which turn off and turn on the complex, respectively. In this mechanism, pyruvate dehydrogenase kinase phosphorylates (using ATP) to target serine residues in E1 subunit, while pyruvate dehydrogenase phosphatase dephosphorylates this subunit, thereby deactivating and activating the complex, respectively.