scholarly journals Variation in the organization and subunit composition of the mammalian pyruvate dehydrogenase complex E2/E3BP core assembly

2011 ◽  
Vol 437 (3) ◽  
pp. 565-574 ◽  
Author(s):  
Swetha Vijayakrishnan ◽  
Philip Callow ◽  
Margaret A. Nutley ◽  
Donna P. McGow ◽  
David Gilbert ◽  
...  
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Catalytic Efficiency ◽  
Fine Tuning ◽  
Subunit Composition ◽  
Glucose Homoeostasis ◽  
Multiple Copies ◽  
Accessory Subunit ◽  
Cross Bridges ◽  
Dehydrogenase Complex

Crucial to glucose homoeostasis in humans, the hPDC (human pyruvate dehydrogenase complex) is a massive molecular machine comprising multiple copies of three distinct enzymes (E1–E3) and an accessory subunit, E3BP (E3-binding protein). Its icosahedral E2/E3BP 60-meric ‘core’ provides the central structural and mechanistic framework ensuring favourable E1 and E3 positioning and enzyme co-operativity. Current core models indicate either a 48E2+12E3BP or a 40E2+20E3BP subunit composition. In the present study, we demonstrate clear differences in subunit content and organization between the recombinant hPDC core (rhPDC; 40E2+20E3BP), generated under defined conditions where E3BP is produced in excess, and its native bovine (48E2+12E3BP) counterpart. The results of the present study provide a rational basis for resolving apparent differences between previous models, both obtained using rhE2/E3BP core assemblies where no account was taken of relative E2 and E3BP expression levels. Mathematical modelling predicts that an ‘average’ 48E2+12E3BP core arrangement allows maximum flexibility in assembly, while providing the appropriate balance of bound E1 and E3 enzymes for optimal catalytic efficiency and regulatory fine-tuning. We also show that the rhE2/E3BP and bovine E2/E3BP cores bind E3s with a 2:1 stoichiometry, and propose that mammalian PDC comprises a heterogeneous population of assemblies incorporating a network of E3 (and possibly E1) cross-bridges above the core surface.

scholarly journals Pyruvate dehydrogenase complex and nicotinamide nucleotide transhydrogenase constitute an energy-consuming redox circuit

2015 ◽  
Vol 467 (2) ◽  
pp. 271-280 ◽  
Author(s):  
Kelsey H. Fisher-Wellman ◽  
Chien-Te Lin ◽  
Terence E. Ryan ◽  
Lauren R. Reese ◽  
Laura A.A. Gilliam ◽  
...  
Keyword(s):  
Energy Expenditure ◽  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Negative Energy ◽  
Fine Tuning ◽  
Metabolic Balance ◽  
Cellular Redox ◽  
Nicotinamide Nucleotide Transhydrogenase ◽  
And Function ◽  
Dehydrogenase Complex

Cellular proteins rely on reversible redox reactions to establish and maintain biological structure and function. How redox catabolic (NAD+/NADH) and anabolic (NADP+/NADPH) processes integrate during metabolism to maintain cellular redox homoeostasis, however, is unknown. The present work identifies a continuously cycling mitochondrial membrane potential (ΔΨm)-dependent redox circuit between the pyruvate dehydrogenase complex (PDHC) and nicotinamide nucleotide transhydrogenase (NNT). PDHC is shown to produce H2O2 in relation to reducing pressure within the complex. The H2O2 produced, however, is effectively masked by a continuously cycling redox circuit that links, via glutathione/thioredoxin, to NNT, which catalyses the regeneration of NADPH from NADH at the expense of ΔΨm. The net effect is an automatic fine-tuning of NNT-mediated energy expenditure to metabolic balance at the level of PDHC. In mitochondria, genetic or pharmacological disruptions in the PDHC–NNT redox circuit negate counterbalance changes in energy expenditure. At the whole animal level, mice lacking functional NNT (C57BL/6J) are characterized by lower energy-expenditure rates, consistent with their well-known susceptibility to diet-induced obesity. These findings suggest the integration of redox sensing of metabolic balance with compensatory changes in energy expenditure provides a potential mechanism by which cellular redox homoeostasis is maintained and body weight is defended during periods of positive and negative energy balance.

scholarly journals Formation of N-hydroxy-N-arylacetamides from nitroso aromatic compounds by the mammalian pyruvate dehydrogenase complex

1993 ◽  
Vol 290 (3) ◽  
pp. 783-790 ◽  
Author(s):  
T Yoshioka ◽  
T Uematsu
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Active Site ◽  
Aromatic Compounds ◽  
Pyruvate Dehydrogenase Complex ◽  
Catalytic Efficiency ◽  
Nitroso Compounds ◽  
Factors Affecting ◽  
Porcine Heart ◽  
Alkyl Groups ◽  
Dehydrogenase Complex

Bovine, human and porcine heart mitochondria and isolated porcine heart pyruvate dehydrogenase complex (PDHC) pyruvate-dependently form N-hydroxy-N-arylacetamides from nitroso aromatic compounds, including carcinogenic 4-biphenyl and 2-fluorenyl derivatives. The PDHC-catalysed formation of N-hydroxyacetanilide (N-OH-AA) from nitrosobenzene (NOB), through a Ping Pong mechanism, is optimum at pH 6.8 and is accelerated by thiamin pyrophosphate, but is inhibited by thiamin thiazolone pyrophosphate and ATP. Km pyruvate in the reaction is independent of pH over the range tested, whereas KmNOB increases at lower pH, owing to ionization of an active-site functional group of pKa 6.3. The enzymic ionization decreases log (Vmax/KmNOB). Isolated pyruvate dehydrogenase (E1), a constitutive enzyme of PDHC, forms N-OH-AA by itself and has comparable kinetic parameters to those of the PDHC-catalysed N-OH-AA formation. The catalytic efficiency of PDHC in the formation of N-hydroxy-N-arylacylamides, due to the steric limitation of the active site of E1, is lowered both by bulky alkyl groups of alpha-oxo acids and by p-substituents (but not an o-substituent) on nitrosobenzenes. These nitroso compounds serve as electrophiles in the reaction in which the reductive acetylation step is rate-limiting. The reaction mechanism and other factors affecting N-hydroxy-N-arylacylamide formation are discussed.

Reengineering of the human pyruvate dehydrogenase complex: from disintegration to highly active agglomerates

2017 ◽  
Vol 474 (5) ◽  
pp. 865-875 ◽  
Author(s):  
Jin Guo ◽  
Samira Hezaveh ◽  
Jana Tatur ◽  
An-Ping Zeng ◽  
Uwe Jandt
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Catalytic Reactions ◽  
Catalytic Core ◽  
Highly Active ◽  
Multiple Copies ◽  
Fundamental Research ◽  
Metabolite Channeling ◽  
Enzyme Cascades ◽  
Dehydrogenase Complex

The pyruvate dehydrogenase complex (PDC) plays a central role in cellular metabolism and regulation. As a metabolite-channeling multi-enzyme complex it acts as a complete nanomachine due to its unique geometry and by coupling a cascade of catalytic reactions using ‘swinging arms'. Mammalian and specifically human PDC (hPDC) is assembled from multiple copies of E1 and E3 bound to a large E2/E3BP 60-meric core. A less restrictive and smaller catalytic core, which is still active, is highly desired for both fundamental research on channeling mechanisms and also to create a basis for further modification and engineering of new enzyme cascades. Here, we present the first experimental results of the successful disintegration of the E2/E3BP core while retaining its activity. This was achieved by C-terminal α-helixes double truncations (eight residues from E2 and seven residues from E3BP). Disintegration of the hPDC core via double truncations led to the formation of highly active (approximately 70% of wildtype) apparently unordered clusters or agglomerates and inactive non-agglomerated species (hexamer/trimer). After additional deletion of N-terminal ‘swinging arms’, the aforementioned C-terminal truncations also caused the formation of agglomerates of minimized E2/E3BP complexes. It is likely that these ‘swinging arm’ regions are not solely responsible for the formation of the large agglomerates.

Regulation of pyruvate dehydrogenase complex activity by reversible phosphorylation

2003 ◽  
Vol 31 (6) ◽  
pp. 1143-1151 ◽  
Author(s):  
M.J. Holness ◽  
M.C. Sugden
Keyword(s):  
Fatty Acid ◽  
Pyruvate Dehydrogenase ◽  
Glucose Oxidation ◽  
Tricarboxylic Acid Cycle ◽  
Pyruvate Dehydrogenase Complex ◽  
Oxidative Decarboxylation ◽  
Acid Cycle ◽  
Essential Component ◽  
Glucose Homoeostasis ◽  
Dehydrogenase Complex

PDC (pyruvate dehydrogenase complex) catalyses the oxidative decarboxylation of pyruvate, linking glycolysis to the tricarboxylic acid cycle. Regulation of PDC determines and reflects substrate preference and is critical to the ‘glucose–fatty acid cycle’, a concept of reciprocal regulation of lipid and glucose oxidation to maintain glucose homoeostasis developed by Philip Randle. Mammalian PDC activity is inactivated by phosphorylation by the PDKs (pyruvate dehydrogenase kinases). PDK inhibition by pyruvate facilitates PDC activation, favouring glucose oxidation and malonyl-CoA formation: the latter suppresses LCFA (long-chain fatty acid) oxidation. PDK activation by the high mitochondrial acetyl-CoA/CoA and NADH/NAD+ concentration ratios that reflect high rates of LCFA oxidation causes blockade of glucose oxidation. Complementing glucose homoeostasis in health, fuel allostasis, i.e. adaptation to maintain homoeostasis, is an essential component of the response to chronic changes in glycaemia and lipidaemia in insulin resistance. We develop the concept that the PDKs act as tissue homoeostats and suggest that long-term modulation of expression of individual PDKs, particularly PDK4, is an essential component of allostasis to maintain homoeostasis. We also describe the intracellular signals that govern the expression of the various PDK isoforms, including the roles of the peroxisome proliferator-activated receptors and lipids, as effectors within the context of allostasis.

scholarly journals Selective proteolysis of the protein X subunit of the bovine heart pyruvate dehydrogenase complex. Effects on dihydrolipoamide dehydrogenase (E3) affinity and enzymic properties of the complex

1991 ◽  
Vol 278 (2) ◽  
pp. 423-427 ◽  
Author(s):  
J C Neagle ◽  
J G Lindsay
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Catalytic Efficiency ◽  
Intact Protein ◽  
Loss Of Function ◽  
Complex Activity ◽  
Bovine Heart ◽  
Protein X ◽  
Dehydrogenase Complex ◽  
Selective Proteolysis

Selective proteolysis of the protein X subunit of native bovine heart pyruvate dehydrogenase complex may be accomplished without loss of overall complex activity. Partial loss of function occurs if Mg2+ and thiamin pyrophosphate are not present during proteinase arg C treatment as these cofactors are necessary to prevent cleavage of the E1 alpha subunit. Specific degradation of component X leads to marked alterations in the general enzymic properties of the complex. Lipoamide dehydrogenase (E3) exhibits a decreased affinity for the core assembly and the complex is much more susceptible to inactivation at high ionic strength. The inactive form of the complex is not readily re-activated by removal of salt. It appears that intact protein X and specifically the presence of its cleaved lipoyl domain is not essential for maintenance of an enzymically active pyruvate dehydrogenase complex. However, this protein has an important structural role in promoting the correct association of E3 with the E2 core assembly, an interaction that is required for optimal catalytic efficiency of the complex.

Regulation of the pyruvate dehydrogenase complex

2006 ◽  
Vol 34 (2) ◽  
pp. 217-222 ◽  
Author(s):  
M.S. Patel ◽  
L.G. Korotchkina
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Redox State ◽  
Pyruvate Dehydrogenase Complex ◽  
Energy Status ◽  
Short Term ◽  
Disease States ◽  
Glucose Homoeostasis ◽  
Specific Distribution ◽  
Dehydrogenase Complex

The PDC (pyruvate dehydrogenase complex) plays a central role in the maintenance of glucose homoeostasis in mammals. The carbon flux through the PDC is meticulously controlled by elaborate mechanisms involving post-translational (short-term) phosphorylation/dephosphorylation and transcriptional (long-term) controls. The former regulatory mechanism involving multiple phosphorylation sites and tissue-specific distribution of the dedicated kinases and phosphatases is not only dependent on the interactions among the catalytic and regulatory components of the complex but also sensitive to the intramitochondrial redox state and metabolite levels as indicators of the energy status. Furthermore, differential transcriptional controls of the regulatory components of PDC further add to the complexity needed for long-term tuning of PDC activity for the maintenance of glucose homoeostasis during normal and disease states.

Molecular architecture of the pyruvate dehydrogenase complex: bridging the gap

2006 ◽  
Vol 34 (5) ◽  
pp. 815-818 ◽  
Author(s):  
M. Smolle ◽  
J.G. Lindsay
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Active Sites ◽  
Pyruvate Dehydrogenase Complex ◽  
Pyruvate Decarboxylase ◽  
Molecular Architecture ◽  
Glucose Homoeostasis ◽  
Bulk Medium ◽  
Substrate Channelling ◽  
Rapid Transfer ◽  
Dehydrogenase Complex

The PDC (pyruvate dehydrogenase complex) is a high-molecular-mass (4–11 MDa) complex of critical importance for glucose homoeostasis in mammals. Its multi-enzyme structure allows for substrate channelling and active-site coupling: sequential catalytic reactions proceed through the rapid transfer of intermediates between individual components and without diffusion into the bulk medium due to its ‘swinging arm’ that is able to visit all PDC active sites. Optimal positioning of individual components within this multi-subunit complex further affects the efficiency of the overall reaction and stability of its intermediates. Mammalian PDC comprises a 60-meric pentagonal dodecahedral dihydrolipoamide (E2) core attached to which are 30 pyruvate decarboxylase (E1) heterotetramers and six dihydrolipoamide (E3) homodimers at maximal occupancy. Stable E3 integration is mediated by an accessory E3-binding protein associated with the E2 core. Association of the peripheral E1 and E3 enzymes with the PDC core has been studied intensively in recent years and has yielded some interesting and substantial differences when compared with prokaryotic PDCs.

Sign in / Sign up

Export Citation Format

Share Document