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.

Enzyme activities of D-glucose metabolism in the fission yeast Schizosaccharomyces pombe

1992 ◽  
Vol 38 (12) ◽  
pp. 1313-1319 ◽  
Author(s):  
C. S. Tsai ◽  
J.-L. Shi ◽  
B. W. Beehler ◽  
B. Beck
Keyword(s):  
Steady State ◽  
Alcohol Dehydrogenase ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Pyruvate Decarboxylase ◽  
Washout Rate ◽  
Synthetase Activity ◽  
Dehydrogenase Complex

The activities of key enzymes that are members of D-glucose metabolic pathways in Schizosaccharomyces pombe undergoing respirative, respirofermentative, and fermentative metabolisms are monitored. The steady-state activities of glycolytic enzymes, except phosphofructokinase, decrease with a reduced efficiency in D-glucose utilization by yeast continuous culture. On the other hand, the enzymic activities of pentose monophosphate pathway reach the maximum when the cell mass production of the cultures is optimum. Enzymes of tricarboxylate cycle exhibit the maximum activities at approximately the washout rate. The steady-state activity of pyruvate dehydrogenase complex increases rapidly when D-glucose is efficiently utilized. By comparison, the activity of pyruvate decarboxylase begins to increase only when ethanol production occurs. Depletion of dissolved oxygen suppresses the activity of pyruvate dehydrogenase complex but facilitates that of pyruvate decarboxylase. Acetate greatly enhances the acetyl CoA synthetase activity. Similarly, ethanol stimulates alcohol dehydrogenase and aldehyde dehydrogenase activities. Evidence for the existence of alcohol dehydrogenase isozymes in the fission yeast is presented. Key words: yeast, glucose-metabolizing enzymes.

scholarly journals Pyruvate Dehydrogenase Activity in Group N Streptococci

1980 ◽  
Vol 33 (1) ◽  
pp. 15 ◽  
Author(s):  
MC Broome ◽  
MP Thomas ◽  
J Hillier ◽  
GR Jago
Keyword(s):  
Dehydrogenase Activity ◽  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Pyruvate Decarboxylase ◽  
Whole Cells ◽  
Streptococcus Lactis ◽  
Dehydrogenase Complex

Pyruvate dehydrogenase activity was detected in whole cells but not in cell-free extracts of Streptococcus lactis. However, the three component enzymes (pyruvate decarboxylase, lipoate acetyltransferase and lipoyl dehydrogenase) of the pyruvate dehydrogenase complex were identified in the cell-free extracts. Whole cells of the three species of group N streptococci formed acetoin and diacetyl only after the pathway forming acetate had become saturated. S. lactis subsp. diacetylactis DRC2 formed more acetoin and diacetyl and less acetate from pyruvate than did S. lactis CW. Strains CIO and DRC2 were able to form acetoin via a-acetolactate or diacetyl and to convert acetoin to butane-2,3-diol. S. cremoris HP was able to form acetoin only via a-acetolactate and could not convert acetoin to butane-2,3cdiol.

Molecular biology of acetyl-CoA metabolism

2000 ◽  
Vol 28 (6) ◽  
pp. 591-593 ◽  
Author(s):  
B. J. Nikolau ◽  
D. J. Oliver ◽  
P. S. Schnable ◽  
E. S. Wurtele
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Pyruvate Decarboxylase ◽  
Acetyl Coa Carboxylase ◽  
Atp Citrate Lyase ◽  
Acetyl Coa ◽  
Acetaldehyde Dehydrogenase ◽  
Citrate Lyase ◽  
Biochemical Genetic ◽  
Dehydrogenase Complex

We have characterized the expression of potential acetyl-CoA-generating genes (acetyl-CoA synthetase, pyruvate decarboxylase, acetaldehyde dehydrogenase, plastidic pyruvate dehydrogenase complex and ATP-citrate lyase), and compared these with the expression of acetyl-CoA-metabolizing genes (heteromeric and homomeric acetyl-CoA carboxylase). These comparisons have led to the development of testable hypotheses as to how distinct pools of acetyl-CoA are generated and metabolized. These hypotheses are being tested by combined biochemical, genetic and molecular biological experiments, which is providing insights into how acetyl-CoA metabolism is regulated.

scholarly journals Domain structure and1H-n.m.r. spectroscopy of the pyruvate dehydrogenase complex of Bacillus stearothermophilus

1984 ◽  
Vol 217 (1) ◽  
pp. 219-227 ◽  
Author(s):  
L C Packman ◽  
R N Perham ◽  
G C K Roberts
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Active Sites ◽  
Bacillus Stearothermophilus ◽  
Inner Core ◽  
Polypeptide Chain ◽  
Pyruvate Dehydrogenase Complex ◽  
Terminal Region ◽  
Enzyme Complex ◽  
Dehydrogenase Complex ◽  
Lipoyl Domain

The pyruvate dehydrogenase complex of Bacillus stearothermophilus was treated with Staphylococcus aureus V8 proteinase, causing cleavage of the dihydrolipoamide acetyltransferase polypeptide chain (apparent Mr 57 000), inhibition of the enzymic activity and disassembly of the complex. Fragments of the dihydrolipoamide acetyltransferase chains with apparent Mr 28 000, which contained the acetyltransferase activity, remained assembled as a particle ascribed the role of an inner core of the complex. The lipoic acid residue of each dihydrolipoamide acetyltransferase chain was found as part of a small but stable domain that, unlike free lipoamide, was able still to function as a substrate for reductive acetylation by pyruvate in the presence of intact enzyme complex or isolated pyruvate dehydrogenase (lipoamide) component. The lipoyl domain was acidic and had an apparent Mr of 6500 (by sedimentation equilibrium), 7800 (by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis) and 10 000 and 20 400 (by gel filtration in the presence and in the absence respectively of 6M-guanidinium chloride). 1H-n.m.r. spectroscopy of the dihydrolipoamide acetyltransferase inner core demonstrated that it did not contain the segments of highly mobile polypeptide chain found in the pyruvate dehydrogenase complex. 1H-n.m.r. spectroscopy of the lipoyl domain demonstrated that it had a stable and defined tertiary structure. From these and other experiments, a model of the dihydrolipoamide acetyltransferase chain is proposed in which the small, folded, lipoyl domain comprises the N-terminal region, and the large, folded, core-forming domain that contains the acetyltransferase active site comprises the C-terminal region. These two regions are separated by a third segment of the chain, which includes a substantial region of polypeptide chain that enjoys high conformational mobility and facilitates movement of the lipoyl domain between the various active sites in the enzyme complex.

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 Lipoic acid residues in a take-over mechanism for the pyruvate dehydrogenase multienzyme complex of Escherichia coli

1981 ◽  
Vol 199 (3) ◽  
pp. 513-520 ◽  
Author(s):  
J N Berman ◽  
G X Chen ◽  
G Hale ◽  
R N Perham
Keyword(s):  
Escherichia Coli ◽  
Lipoic Acid ◽  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Pyruvate Decarboxylase ◽  
Enzymic Activity ◽  
Enzyme Mechanism ◽  
Enzyme Complex ◽  
Complex Activity ◽  
Dehydrogenase Complex

The pyruvate dehydrogenase complex of Escherichia coli contains two lipoic acid residues per dihydrolipoamide acetyltransferase chain, and these are known to engage in the part-reactions of the enzyme. The enzyme complex was treated with trypsin at pH 7.0, and a partly proteolysed complex was obtained that had lost almost 60% of its lipoic acid residues although it retained 80% of its pyruvate dehydrogenase-complex activity. When this complex was treated with N-ethylmaleimide in the presence of pyruvate and the absence of CoASH, the rate of modification of the remaining S-acetyldihydrolipoic acid residues was approximately equal to the accompanying rate of loss of enzymic activity. This is in contrast with the native pyruvate dehydrogenase complex, where under the same conditions modification proceeds appreciably faster than the loss of enzymic activity. The native pyruvate dehydrogenase complex was also treated with lipoamidase prepared from Streptococcus faecalis. The release of lipoic acid from the complex followed zero-order kinetics for most of the reaction, whereas the accompanying loss of pyruvate dehydrogenase-complex activity lagged substantially behind. These results eliminate a model for the enzyme mechanism in which specifically one of the two lipoic acid residues on each dihydrolipoamide acetyltransferase chain is essential for the reaction. They are consistent with a model in which the dihydrolipoamide acetyltransferase component contains more lipoic acid residues than are required to serve the pyruvate decarboxylase subunits under conditions of saturating substrates, enabling the function of an excised or inactivated lipoic acid residue to be taken over by another one. Unusual structural properties of the enzyme complex might permit this novel feature of the enzyme mechanism.

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