THE COMPLEX FATE OF α-KETOACIDS

▪ Abstract Plant cells are unique in that they contain four species of α-ketoacid dehydrogenase complex: plastidial pyruvate dehydrogenase, mitochondrial pyruvate dehydrogenase, α-ketoglutarate (2-oxoglutarate) dehydrogenase, and branched-chain α-ketoacid dehydrogenase. All complexes include multiple copies of three components: an α-ketoacid dehydrogenase/decarboxylase, a dihydrolipoyl acyltransferase, and a dihydrolipoyl dehydrogenase. The mitochondrial pyruvate dehydrogenase complex additionally includes intrinsic regulatory protein-kinase and -phosphatase enzymes. The acyltransferases form the intricate geometric core structures of the complexes. Substrate channeling plus active-site coupling combine to greatly enhance the catalytic efficiency of these complexes. These α-ketoacid dehydrogenase complexes occupy key positions in intermediary metabolism, and a basic understanding of their properties is critical to genetic and metabolic engineering. The current status of knowledge of the biochemical, regul...