scholarly journals The effects of calcium ions and adenine nucleotides on the activity of pig heart 2-oxoglutarate dehydrogenase complex

1979 ◽  
Vol 180 (3) ◽  
pp. 533-544 ◽  
Author(s):  
J G McCormack ◽  
R M Denton
Keyword(s):  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Product Inhibition ◽  
Maximal Velocity ◽  
Brown Adipose ◽  
Dehydrogenase System ◽  
Oxoglutarate Dehydrogenase ◽  
Ph Range ◽  
Fold Activation ◽  
Dehydrogenase Complex

1. The effects of Ca2+ (mainly by using EGTA buffers), pH, ATP and ADP on the activity of the 2-oxoglutarate dehydrogenase complex from pig heart were explored. 2. Ca2+ (about 30 micrometer) resulted in a decrease in the apparent Km for 2-oxoglutarate from 2.1 to 0.16 mM (at pH 7) without altering the maximal velocity. At 0.1 mM-oxoglutarate there was a 4–5-fold activation by Ca2+, with an apparent Km for Ca2+ of 1.2 micrometer. A similar activation was also observed with Sr2+ (Km 15.1 micrometer), but not wised markedly from pH 7.4 TO 6.6. The effects of Ca2+ remained evident over this pH range. 4. In the presence of Mg2+, ATP resulted in a marked increase in the apparent Km for oxoglutarate, whereas ADP greatly decreased thisp arameter. The concentrations of adenine nucleotide required for half-maximal effects were about 10 micrometer in each case. 5. The effects of the adenine nucleotides and Ca2+ on the apparent Km for oxoglutarate appeared to be essentially independent of each other, reversible, and demonstrable in the presence of end product inhibition by NADH and obtained. 6. Effects similar to those described above were also observed on the activity of 2-oxoglutarate dehydrogenase from rat heart and brown adipose tissue. 7. We discuss the mechanisms controlling this enzyme's activity and compare these regulatory features with those of NAD-isocitrate dehydrogenase and the pyruvate dehydrogenase system, which are also sensitive to Ca2+ and adenine nucleotides.

Regulation of VO2 in red muscle: do current biochemical hypotheses fit in vivo data?

1989 ◽  
Vol 256 (4) ◽  
pp. R898-R906 ◽  
Author(s):  
R. J. Connett ◽  
C. R. Honig
Keyword(s):  
Intracellular Ph ◽  
Adenine Nucleotide ◽  
Energy State ◽  
Adenine Nucleotides ◽  
Wide Range ◽  
Glycolytic Intermediates ◽  
Red Muscle ◽  
Ph Range

Observations used to test biochemical models of the regulation of O2 consumption (VO2) by cytosolic phosphate energy state must include a change in intracellular pH and/or a change in the adenine nucleotide or phosphate pools [Connett, R. J. Analysis of metabolic control: new insights using a scaled creatine kinase model. Am. J. Physiol. 254 (Regulatory Integrative Comp. Physiol. 23): R949-R959, 1988]. Data were collected over a wide range of energy turnover from canine muscles in situ. Intracellular PO2, glycolytic intermediates, adenine nucleotides, creatine, phosphocreatine (PCr), phosphate, and intracellular pH were determined for each muscle. PO2 was used to eliminate muscles in which VO2 could have been O2 limited (PO2 less than 0.5 Torr). This removed an important source of heterogeneity. Because adenine nucleotide and phosphate pools were constant relative to the creatine pool, discrimination among models depended solely on pH. The observed pH range from 7.2 to 5.9 did not permit separation of [PCr] from log[( ATP4-]/[ADP3-][H2PO4-]) (phosphorylation potential) as a regulatory parameter for VO2. However, [ADP] could be eliminated as an independent regulator. Because 90% of variability in VO2 was accounted for by phosphate energetics, an independent redox component must be small when intracellular PO2 greater than 0.5 Torr.

scholarly journals Regulation of NAD+-linked isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase by Ca2+ ions within toluene-permeabilized rat heart mitochondria. Interactions with regulation by adenine nucleotides and NADH/NAD+ ratios

1988 ◽  
Vol 252 (1) ◽  
pp. 181-189 ◽  
Author(s):  
G A Rutter ◽  
R M Denton
Keyword(s):  
Isocitrate Dehydrogenase ◽  
Rat Heart ◽  
Adenine Nucleotides ◽  
Heart Mitochondria ◽  
Maximal Effect ◽  
Dehydrogenase System ◽  
Rat Heart Mitochondria ◽  
Oxoglutarate Dehydrogenase ◽  
Intact Heart

1. Toluene-permeabilized rat heart mitochondria have been used to study the regulation of NAD+-linked isocitrate dehydrogenase and 2-oxoglutarate dehydrogenase by Ca2+, adenine and nicotinamide nucleotides, and to compare the properties of the enzymes in situ, with those in mitochondrial extracts. 2. Although K0.5 values (concn. giving half-maximal effect) for Ca2+ of 2-oxoglutarate dehydrogenase were around 1 microM under all conditions, corresponding values for NAD+-linked isocitrate dehydrogenase were in the range 5-43 microM. 3. For both enzymes, K0.5 values for Ca2+ observed in the presence of ATP were 3-10-fold higher than those in the presence of ADP, with values increasing over the ADP/ATP range 0.0-1.0. 4. 2-Oxoglutarate dehydrogenase was less sensitive to inhibition by NADH when assayed in permeabilized mitochondria than in mitochondrial extracts. Similarly, the Km of NAD+-linked isocitrate dehydrogenase for threo-Ds-isocitrate was lower in permeabilized mitochondria than in extracts under all the conditions investigated. 5. It is concluded that in the intact heart Ca2+ activation of NAD+-linked isocitrate dehydrogenase may not necessarily occur in parallel with that of the other mitochondrial Ca2+-sensitive enzymes, 2-oxoglutarate dehydrogenase and the pyruvate dehydrogenase system.

Rat cardiac myocyte adenosine transport and metabolism

1987 ◽  
Vol 252 (1) ◽  
pp. H54-H63 ◽  
Author(s):  
D. A. Ford ◽  
M. J. Rovetto
Keyword(s):  
Metabolic Flux ◽  
Cardiac Myocyte ◽  
Ventricular Myocytes ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Nucleotide Metabolism ◽  
Adenosine Kinase ◽  
Maximal Velocity ◽  
Extracellular Adenosine ◽  
Minimum Estimate

Based on the importance of myocardial adenosine and adenine nucleotide metabolism, the adenosine salvage pathway in ventricular myocytes was studied. Accurate estimates of transport rates, separate from metabolic flux, were determined. Adenosine influx was constant between 3 and 60 s. Adenosine metabolism maintained intracellular adenosine concentrations less than 10% of the extracellular adenosine concentrations and thus unidirectional influx could be measured. Myocytes transported adenosine via saturable [Michaelis constant = 6.2 +/- 2.1 microM and maximal velocity (Vmax) = 9.58 +/- 0.98 X 10(-1) pmol X mg protein-1 X s-1] and nonsaturable (rate constant = 1.8 X 10(-3)/s) processes. A minimum estimate of the Vmax of myocytic adenosine kinase (2 pmol X mg protein-1 X s-1) indicated the saturable component of adenosine influx was independent of adenosine kinase activity. Saturable transport was inhibited by nitrobenzylthioinosine and verapamil (inhibitor constant = 17 +/- 5 microM). Extracellular adenosine taken up by myocytes was rapidly phosphorylated to adenine nucleotides. Not all extracellular adenosine, though, was phosphorylated on entering myocytes, since free, as opposed to protein-bound, intracellular adenosine was detected after digitonin extraction of cells in the presence of 1 mM ethylene-diaminetetraacetic acid.

Studies on the regulation of the human E1 subunit of the 2-oxoglutarate dehydrogenase complex, including the identification of a novel calcium-binding site

2014 ◽  
Vol 459 (2) ◽  
pp. 369-381 ◽  
Author(s):  
Craig T. Armstrong ◽  
J. L. Ross Anderson ◽  
Richard M. Denton
Keyword(s):  
Energy Metabolism ◽  
Binding Site ◽  
Calcium Binding ◽  
Adenine Nucleotides ◽  
Calcium Binding Site ◽  
Site Of Action ◽  
Oxoglutarate Dehydrogenase ◽  
Dehydrogenase Complex

The oxoglutarate dehydrogenase complex regulates energy metabolism through its sensitivity to adenine nucleotides, NADH and Ca2+. In the present study, we show definitively that the E1 subunit is the site of action for these regulators, and identify the Ca2+-binding site.

The Platelet of the Newborn Infant – Adenine Nucleotide Metabolism and Release

1980 ◽  
Vol 43 (02) ◽  
pp. 099-103 ◽  
Author(s):  
J M Whaun ◽  
P Lievaart ◽  
Keyword(s):  
Newborn Infant ◽  
Adenine Nucleotide ◽  
Platelet Rich Plasma ◽  
Adenine Nucleotides ◽  
Newborn Infants ◽  
Specific Radioactivity ◽  
Nucleotide Metabolism ◽  
Breakdown Product ◽  
Term Infants ◽  
Adenine Nucleotide Metabolism

SummaryBlood from normal full term infants, mothers and normal adults was collected in citrate. Citrated platelet-rich plasma was prelabelled with 3H-adenine and reacted with release inducers, collagen and adrenaline. Adenine nucleotide metabolism, total adenine nucleotide levels and changes in sizes of these pools were determined in platelets from these three groups of subjects.At rest, the platelet of the newborn infant, compared to that of the mother and normal adult, possessed similar amounts of adenosine triphosphate (ATP), 4.6 ± 0.2 (SD), 5.0 ± 1.1, 4.9 ± 0.6 µmoles ATP/1011 platelets respectively, and adenosine diphosphate (ADP), 2.4 ± 0.7, 2.8 ± 0.6, 3.0 ± 0.3 umoles ADP/1011 platelets respectively. However the marked elevation of specific radioactivity of ADP and ATP in these resting platelets indicated the platelet of the neonate has decreased adenine nucleotide stores.In addition to these decreased stores of adenine nucleotides, infant platelets showed significantly impaired release of ADP and ATP on exposure to collagen. The release of ADP in infants, mothers, and other adults was 0.9 ± 0.5 (SD), 1.5 ± 0.5, 1.5 ± 0.1 umoles/1011 platelets respectively; that of ATP was 0.6 ± 0.3, 1.0 ± 0.1,1.3 ± 0.2 µmoles/1011 platelets respectively. With collagen-induced release, platelets of newborn infants compared to those of other subjects showed only slight increased specific radioactivities of adenine nucleotides over basal levels. The content of metabolic hypoxanthine, a breakdown product of adenine nucleotides, increased in both platelets and plasma in all subjects studied.In contrast, with adrenaline as release inducer, the platelets of the newborn infant showed no adenine nucleotide release, no change in total ATP and level of radioactive hypoxanthine, and minimal change in total ADP. The reason for this decreased adrenaline reactivity of infant platelets compared to reactivity of adult platelets is unknown.Infant platelets may have different membranes, with resulting differences in regulation of cellular processes, or alternatively, may be refractory to catecholamines because of elevated levels of circulating catecholamines in the newborn period.

scholarly journals L-Arginine Intake Effect on Adenine Nucleotide Metabolism in Rat Parenchymal and Reproductive Tissues

2012 ◽  
Vol 2012 ◽  
pp. 1-4 ◽  
Author(s):  
G. Kocic ◽  
J. Nikolic ◽  
T. Jevtovic-Stoimenov ◽  
D. Sokolovic ◽  
H. Kocic ◽  
...  
Keyword(s):  
Adenosine Deaminase ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Tissue Growth ◽  
Nucleotide Metabolism ◽  
Amp Deaminase ◽  
Male Impotence ◽  
Adenine Nucleotide Metabolism ◽  
Adenosine Concentration ◽  
Male Wistar Rats

L-arginine is conditionally essetcial amino acid, required for normal cell growth, protein synthesis, ammonia detoxification, tissue growth and general performance, proposed in the treatment of men sterility and prevention of male impotence. The aim of the present paper was to estimate the activity of the enzymes of adenine nucleotide metabolism:5′-nucleotidase (5′-NU), adenosine deaminase (ADA), AMP deaminase, and xanthine oxidase (XO), during dietary intake of L-arginine for a period of four weeks of male Wistar rats. Adenosine concentration in tissues is maintained by the relative activities of the adenosine-producing enzyme,5′-NU and the adenosine-degrading enzyme-ADA adenosine deaminase. Dietary L-arginine intake directed adenine nucleotide metabolism in liver, kidney, and testis tissue toward the activation of adenosine production, by increased5′-NU activity and decreased ADA activity. Stimulation of adenosine accumulation could be of importance in mediating arginine antiatherosclerotic, vasoactive, immunomodulatory, and antioxidant effects. Assuming that the XO activity reflects the rate of purine catabolism in the cell, while the activity of AMP deaminase is of importance in ATP regeneration, reduced activity of XO, together with the increased AMP-deaminase activity, may suggest that adenine nucleotides are presumably directed to the ATP regenerating process during dietary L-arginine intake.

P4-154: Succinyl phosphonate, a protector of the 2-oxoglutarate dehydrogenase complex, corrects behavioral impairments in rats exposed to hypoxia or ethanol

2009 ◽  
Vol 5 (4S_Part_16) ◽  
pp. P476-P477 ◽  
Author(s):  
Victoria I. Bunik ◽  
Maxim Lovat ◽  
Alexandra Groznaya ◽  
Anastasia Graf ◽  
Tatiana Dunaeva ◽  
...  
Keyword(s):  
Oxoglutarate Dehydrogenase ◽  
Behavioral Impairments ◽  
Dehydrogenase Complex

scholarly journals Intracellular Mg2+regulates ADP phosphorylation and adenine nucleotide synthesis in human erythrocytes

1998 ◽  
Vol 274 (5) ◽  
pp. E920-E927 ◽  
Author(s):  
Sarah Page ◽  
Michael Salem ◽  
Maren R. Laughlin
Keyword(s):  
Adenine Nucleotide ◽  
Phosphoglycerate Kinase ◽  
Pentose Phosphate ◽  
Human Erythrocytes ◽  
Maximal Velocity ◽  
Nucleotide Synthesis ◽  
Ion Concentrations ◽  
Net Flux ◽  
Normal Fluctuations ◽  
Phosphorylation Rate

13C- and31P-NMR were used in methylene blue-treated human erythrocytes to determine the dependence on intracellular Mg2+concentration ([Mg2+]i) of the pentose phosphate pathway (PPP), the glycolytic pathway, and adenine nucleotide synthesis. The PPP flux had an [Mg2+]iat half-maximal velocity ([Mg2+]i,0.5) of 0.02 mM, well below the physiological range (0.2–0.7 mM). Flux through the PPP was reduced at higher [Mg2+]ias flux through phosphofructokinase was increased ([Mg2+]i,0.5= 0.16 mM). [Mg2+]i,0.5of phosphoglycerate kinase flux, which equals net ADP phosphorylation rate, was 0.27 mM, well within the physiological [Mg2+]irange. The rate of adenine nucleotide synthesis from [2-13C]glucose-derived ribose 5-phosphate and exogenous adenine also exhibited dependence on [Mg2+]ibut was not saturable up to 1.6 mM. Therefore, net flux through the PPP and glycolytic pathways in erythrocytes is not strongly dependent on [Mg2+]iat physiological ion concentrations, but both ADP phosphorylation and adenine nucleotide synthesis are likely to be regulated by normal fluctuations in [Mg2+]i.

scholarly journals Mitochondrial Protein Lipoylation and the 2-Oxoglutarate Dehydrogenase Complex Controls HIF1α Stability in Aerobic Conditions

2016 ◽  
Vol 24 (5) ◽  
pp. 740-752 ◽  
Author(s):  
Stephen P. Burr ◽  
Ana S.H. Costa ◽  
Guinevere L. Grice ◽  
Richard T. Timms ◽  
Ian T. Lobb ◽  
...  
Keyword(s):  
Mitochondrial Protein ◽  
Aerobic Conditions ◽  
Oxoglutarate Dehydrogenase ◽  
Dehydrogenase Complex

scholarly journals Effect of adenine nucleotides on myo-inositol-1,4,5-trisphosphate-induced calcium release

1997 ◽  
Vol 325 (3) ◽  
pp. 661-666 ◽  
Author(s):  
Ludwig MISSIAEN ◽  
Jan B. PARYS ◽  
Humbert DE SMEDT ◽  
Ilse SIENAERT ◽  
Henk SIPMA ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Binding Site ◽  
Calcium Release ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Release Process ◽  
A7r5 Cells ◽  
Channel Opening ◽  
Inositol 1,4,5 Trisphosphate

The effects of a whole series of adenine nucleotides on Ins(1,4,5)P3-induced Ca2+ release were characterized in permeabilized A7r5 smooth-muscle cells. Several adenine nucleotides activated the Ins(1,4,5)P3 receptor. It was observed that 3′-phosphoadenosine 5′-phosphosulphate, CoA, di(adenosine-5′)tetraphosphate (Ap4A) and di(adenosine-5′)pentaphosphate (Ap5A) were more effective than ATP. Ap4A and Ap5A also interacted with a lower EC50 than ATP. In order to find out how these adenine nucleotides affected Ins(1,4,5)P3-induced Ca2+ release, we have measured their effect on the response of permeabilized A7r5 cells to a progressively increasing Ins(1,4,5)P3 concentration. Stimulatory ATP and Ap5A concentrations had no effect on the threshold Ins(1,4,5)P3 concentration for initiating Ca2+ release, but they stimulated Ca2+ release in the presence of supra-threshold Ins(1,4,5)P3 concentrations by increasing the co-operativity of the release process. Inhibition of the Ins(1,4,5)P3-induced Ca2+ release at higher ATP concentrations was associated with a further increase in co-operativity and also with a shift in threshold towards higher Ins(1,4,5)P3 concentrations. ATP had no effect on the non-specific Ca2+ leak in the absence of Ins(1,4,5)P3. We conclude that the adenine-nucleotide-binding site can be activated by many different adenine nucleotides. Binding of these compounds to the transducing domain of the Ins(1,4,5)P3 receptor increases the efficiency of transmitting Ins(1,4,5)P3 binding to channel opening. The inhibition by high ATP concentrations is exerted at a different site, related to Ins(1,4,5)P3 binding.

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