2-Oxo acid dehydrogenase multienzyme complexes. The central role of the lipoyl domain

2-Oxo acid dehydrogenase complexes are composed of multiple copies of at least three different enzymes, 2-oxo acid dehydrogenase, dihydrolipoyl acyltransferase and dihydrolipoamide dehydrogenase. The acyltransferase component harbours all properties required for multienzyme catalysis: it forms a large multimeric core, it contains binding sites for the peripheral components, the acyltransferase active site and mobile substrate carrying lipoyl domains that couple the active sites. In the past years these complexes have disclosed many of their secrets, providing currently a wealth of information on macromolecular structure, assembly and symmetry, active-site coupling, conformational mobility, substrate specificity and metabolic regulation. In this review we will discuss developments concerning the structural and mechanistic features of the 2-oxo acid dehydrogenase complexes, with special emphasis on the structure and role of the lipoyl domains in the complex.