Molecular biology and biochemistry of pyruvate dehydrogenase complexes ¹

Abstract

In most organisms, the pyruvate dehydrogenase complex catalyzes the pivotal irreversible reaction that leads to the consumption of glucose in the aerobic, energy-generating pathways. A combination of biochemical and molecular biology studies have greatly expanded our understanding of the overall structural organization of this multicomponent system, delineated the locations and elucidated the functions of structural domains of the catalytic components, and revealed significant evolutionary changes. Important to this progress was the deduction of the primary amino acid sequences from cDNA clones for each of the catalytic components from several species. The greatest detail is available for the FAD-containing dihydrolipoamide dehydrogenase component, which is the only component for which tertiary structure information has recently emerged. For the dihydrolipoamide acetyltransferase core component, a similar but species-variable multidomain structure is established that is responsible for the distinct architectures of the inner cores, the peripheral binding of the other components, and the conveyance of reaction intermediates between distantly separated active sites. A second lipoyl-bearing component, protein X, has been shown to play a critical role in the organization and function of the complex from many higher organisms. Although much is known about the means of effector modulation of mammalian complex activity, identification of the signal eliciting its regulation by insulin still poses an exciting challenge.

Changes in dihydrolipoamide dehydrogenase expression and activity during postnatal development and aging in the rat brain

“…Structurally, the active form of DLDH is a stable homodimer, with each monomer possessing a non-covalently but tightly bound FAD molecule, a transiently bound NAD + or NADH molecule, and a redox active center containing two cysteine residues (Cys-45 and Cys-50 in both human and rat) that are directly engaged in thiol-disulfide exchange reactions during catalysis (Brautigam, et al, 2005, Ciszak, et al, 2006, Thorpe and Williams, 1976, Williams, 1992. In vivo, DLDH oxidizes dihydrolipoamide that is covalently linked to acyltransferase using NAD + as the electron acceptor, leading to the release of NADH (Patel and Roche, 1990, Vettakkorumakankav and Patel, 1996, Williams, 1992. This reaction is usually referred to as the forward reaction of DLDH, as opposed to the reverse reaction, in which DLDH catalyzes the oxidation of NADH using lipoamide as the electron acceptor.…”

The effect of phosphorylation on pyruvate dehydrogenase

“…PDC from eucaryotes comprises three catalytic components (El, E2, and E3) as well as component X essential to the E2 E3 interaction [1,2]. The E1 component catalyzes the rate-limiting reaction, namely, thiamine pyrophosphate (TPP)-dependent decarboxylation of pyruvate to produce 2-hydroxyethyl-TPP (HETPP) and reductive acetylation of lipoic acid residues covalently bound to E2.…”

Nematode pyruvate dehydrogenase kinases: role of the C-terminus in binding to the dihydrolipoyl transacetylase core of the pyruvate dehydrogenase complex

“…The mammalian E2 contains two distinct lipoyl domains (L1 and L2) located at the N-terminus [38,39]. It has been clearly demonstrated that the mammalian PDK binds to the internal lipoyl domain (L2), perhaps through a highly charged region at the C-terminus, and PDK binding requires the presence of the lipoyl prosthetic group [4,12,40].…”