Abstract
The 2-oxoacid dehydrogenase complexes (ODHc) consist of multiple copies of three enzyme components: E1, a 2-oxoacid decarboxylase; E2, dihydrolipoyl acyl-transferase; and E3, dihydrolipoyl dehydrogenase, that together catalyze the oxidative decarboxylation of 2-oxoacids, in the presence of thiamin diphosphate (ThDP), coenzyme A (CoA), Mg2+ and NAD+, to generate CO2, NADH and the corresponding acyl-CoA. The structural scaffold of the complex is provided by E2, with E1 and E3 bound around the periphery. The three principal members of the family are pyruvate dehydrogenase (PDHc), 2-oxoglutarate dehydrogenase (OGDHc) and branched-chain 2-oxo acid dehydrogenase (BCKDHc). In this review, we report application of NMR-based approaches to both mechanistic and structural issues concerning these complexes. These studies revealed the nature and reactivity of transient intermediates on the enzymatic pathway and provided site-specific information on the architecture and binding specificity of the domain interfaces using solubilized truncated domain constructs of the multi-domain E2 component in its interactions with the E1 and E3 components. Where studied, NMR has also provided information about mobile loops and the possible relationship of mobility and catalysis.
Highlights
The 2-oxoacid dehydrogenase complexes (ODHc) represent the classic examples of multienzyme complexes
NMR approaches applied on these important multienzyme complexes, which provided an integrated view of many facets, from studies of organic catalysis within the protein structure to general principles governing these giant multiprotein catalytic machines
The E3-binding protein (E3BP) is homologous to E2 subunits and includes a single lipoyl domain followed by a peripheral-subunit-binding domain (PSBD) and the catalytic domain, which is devoid of transacetylase activity required to generate acetyl-coenzyme A (CoA) [23,24] (2) The activities of both mammalian PDHc and BCKDHc are subject to regulation by specific kinases (PDK, BDK) and phosphatases (PDP, BDP) [25,26,27] which control the activity of the complex by reversible phosphorylation/dephosphorylation of serine side chains in E1
Summary
The 2-oxoacid dehydrogenase complexes (ODHc) represent the classic examples of multienzyme complexes. They have molecular masses of 4–10 MDa and they act as ‘macromolecular machines’ in which the subunit associations serve to co-localize the enzymes, and couple their activities to channel substrates and products. Each ODHc occupies a key position in intermediary metabolism and their activity is under stringent control by hormones and dietary factors. These complexes have a very similar design and they all catalyze the decarboxylation of 2-oxoacids to produce acyl-coenzyme A (acyl-CoA), NADH, and CO2 by similar coupled multistep reaction mechanisms (Scheme 1). NMR approaches applied on these important multienzyme complexes, which provided an integrated view of many facets, from studies of organic catalysis within the protein structure to general principles governing these giant multiprotein catalytic machines
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