Octopus mantle citrate synthase

1976 ◽  
Vol 54 (6) ◽  
pp. 886-891 ◽  
Author(s):  
J. H. A. Fields ◽  
H. Guderley ◽  
K. B. Storey ◽  
P. W. Hochachka
Keyword(s):  
Citrate Synthase ◽  
Specific Activity ◽  
Energy Charge ◽  
Krebs Cycle ◽  
Fold Increase ◽  
Adenylate Energy Charge ◽  
Michaelis Constant ◽  
Acetyl Coa ◽  
Muscle Work ◽  
Krebs Cycle Intermediates

Citrate synthase (EC 4.1.3.7) in mantle muscle of the octopus, Octopus cyanea, occurs in relatively low specific activity and is largely independent of pH between 7.5 and 9.0. Catalytic activity is regulated by the adenylate energy charge and by at least two Krebs cycle intermediates, α-ketoglutarate and citrate. Of the adenylates, ATP is by far the most potent inhibitor, at near-physiological concentrations (4 mM), causing almost a 20-fold increase in the Michaelis constant for acetyl-CoA. Citrate and α-ketoglutarate, on the other hand, are competitive with respect to oxaloacetate, rather than acetyl-CoA, and bring about large increases in the Michaelis constant for oxaloacetate. The regulatory properties of citrate synthase allow a curtailment of carbon flow into the Krebs cycle during periods of burst muscle work, when mantle anaerobic glycolysis is strongly activated.

The effect of soaking injury in seeds of Phaseolus vulgaris L. on germination, respiration and adenylate energy charge

1998 ◽  
Vol 8 (1) ◽  
pp. 17-28 ◽  
Author(s):  
Johan C. Pretorius ◽  
J. G. Chris Small ◽  
Kurt V. Fagerstedt
Keyword(s):  
Phaseolus Vulgaris ◽  
Energy Charge ◽  
Krebs Cycle ◽  
Threshold Value ◽  
Adenylate Energy Charge ◽  
Respiratory Pathway ◽  
Available Energy ◽  
Saturated Water ◽  
Atp Levels ◽  
Rate Of Oxygen Consumption

AbstractSubmerging Phaseolus vulgaris cv. Top Crop seed in air-saturated water for 16 h markedly depresses subsequent germination. This is termed soaking injury. The postulate by Norton (1986) that soak-injured seeds merely run out of available energy was investigated. Soaking in air-saturated water reduced the total respiration (VT; in terms of O2 uptake) of excised axes and cotyledons resulting in lower ATP levels. The contribution of both the mitochondrial cytochrome respiratory pathway (VCYT) and the alternative respiratory pathway (VALT) to the total respiration (VT) was significantly lower in these axes. However, the adenylate energy charge (AEC) values for both axes and cotyledons excised from soak-injured seeds did not drop below 0.6, the threshold value indicating death of plant material. Differences between the ultrastructure of mitochondria in the radicle tips of axes from unsoaked and water-soaked seeds were observed. However, the capacity to operate the Krebs cycle was similar in all axes and soak-injured seeds were still capable of germinating when the testas were removed or the seeds dried. This means that axes contained a sufficient amount of carbohydrates and potential energy to germinate after soaking. Moreover, soak-injured seeds produced ethanol at a rate which was five times higher than that of unsoaked control seeds, both during the soaking and post-soaking periods. Together with the low rate of oxygen consumption by soak-injured seeds during the same soaking and incubation time, it appears that soak-injured seeds lack the potential to switch from an anaerobic to an aerobic respiration pattern causing low ATP levels in these axes. It is speculated that the latter seems to be the result of limited pyruvate supply, probably due to accelerated and prolonged fermentation or futile combustion through other pathways or both.

Changes in nucleotide pools during conidial germination in Neurospora crassa

1981 ◽  
Vol 59 (11-12) ◽  
pp. 899-905 ◽  
Author(s):  
Richard L. Sabina ◽  
Paulette Dalke ◽  
Alan R. Hanks ◽  
Jane M. Magill ◽  
Clint W. Magill
Keyword(s):  
Neurospora Crassa ◽  
Adenine Nucleotide ◽  
Energy Charge ◽  
Fold Increase ◽  
Conidial Germination ◽  
Adenylate Energy Charge ◽  
Wild Type ◽  
Nucleotide Pools ◽  
Nucleotide Sugars ◽  
Purine Pathway

The acid-soluble nucleotide pools of wild type and several adenine auxotrophs of Neurospora crassa were studied immediately prior to and during conidial germination in the presence of adenine. A two- to four-fold increase in most nucleotide pools was observed after 6 h of germination at 33 °C indicating a general increase in nucleotide pools during this developmental period. The largest components of the acid-soluble nucleotide pools were uracil-containing nucleotide–sugars, which are precursors of chitin and glucan, the major constituents of cell walls. On removal of adenine, the UDP–sugar pools decreased significantly, in adenine auxotrophs, while the pools of UTP increased significantly. ATP levels increased approximately twofold in the first 6 h of germination. After 1 h without exogenous adenine, ATP dropped twofold or more in adenine auxotrophs but not in wild type. There was a net decrease in all adenine nucleotide pools during adenine starvation and a much greater decrease was seen in adenine auxotrophs than in wild type. The adenylate energy charge remained stable despite major changes in the adenylate pools.Accumulation of intermediates was observed in germinated conidia from purine auxotrophs blocked at various steps in the purine pathway. IMP accumulated in ungerminated and in starved conidia of the adenine-8 (ad-8) strain. Ungerminated conidia of the ad-5 strain contained a large pool of 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) while the ad-1 strain had smaller amounts of AICAR, but significantly more than any other strain tested. The AICAR pools disappeared from ad-5 and ad-1 in the presence of 50 mg histidine/100 mL. Similarly the IMP pools in ad-8 decreased markedly in the presence of histidine, indicating that the contribution from the histidine biosynthetic pathway to purine nucleotide formation is significant.

Effects of 5-hydroxytryptamine on carbohydrate metabolism in Hymenolepis diminuta (Cestoda)

1983 ◽  
Vol 61 (2) ◽  
pp. 137-143 ◽  
Author(s):  
M. S. Rahman ◽  
D. F. Mettrick ◽  
R. B. Podesta
Keyword(s):  
Carbohydrate Metabolism ◽  
Gas Phase ◽  
Specific Activity ◽  
Energy Charge ◽  
Hymenolepis Diminuta ◽  
Total Carbon ◽  
Adenylate Energy Charge ◽  
Acetate Excretion ◽  
Carbon Transfer ◽  
Adenine Nucleotide Pool

Under in vitro anaerobic and aerobic incubations the presence of 5-hydroxytryptamine (5-HT) resulted in an accelerated rate of carbon transfer through the carbohydrate metabolic pathways of Hymenolepis diminuta resulting in an increase in worm tissue total carbon pools. Under aerobic incubation, levels of phosphoglycerates, phosphoenolpyruvate (PEP), and pyruvate were significantly increased over the corresponding levels under anaerobic incubation. Excreted end products of carbohydrate metabolism also differed significantly depending on the gas phase and the presence of 5-HT. Under atmospheric (21%) oxygen concentrations excreted levels of lactate, succinate, and acetate were all significantly elevated; under a 95% O2–5% CO2 gas phase only lactate excretion was increased, and under a 95% N2–5% CO2 gas phase only succinate and acetate excretion increased. The presence of oxygen reduced acetate excretion by up to 55% and under the 95% O2–5% CO2 gas phase succinate excretion was reduced 48%. Irrespective of gas phase or the presence of 5-HT, adenine nucleotide pool sizes and the adenylate energy charge remained constant. The addition of 5-HT had no significant effect in increasing the specific activity of phosphofructokinase (PFK). In the presence of ATP the addition of cAMP increased PFK activity by up to 48%; AMP enhanced the enzyme activity by up to 69%, irrespective of the presence or absence of 5-HT. These results are discussed in terms of the effects of 5-HT, gas phase, and nucleotide pools on the motility, metabolism, and control of H. diminuta, and of other parasites which respond to 5-HT.

H55N polymorphism as a likely cause of variation in citrate synthase activity of mouse skeletal muscle

2010 ◽  
Vol 42A (2) ◽  
pp. 96-102 ◽  
Author(s):  
Aivaras Ratkevicius ◽  
Andrew M. Carroll ◽  
Audrius Kilikevicius ◽  
Tomas Venckunas ◽  
Kevin T. McDermott ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Protein Content ◽  
Citrate Synthase ◽  
Genomic Sequence ◽  
Krebs Cycle ◽  
In Silico Analysis ◽  
Inbred Strains ◽  
Mrna Levels ◽  
Acetyl Coa ◽  
C Protein

Citrate synthase (CS) is an enzyme of the Krebs cycle that plays a key role in mitochondrial metabolism. The aim of this study was to investigate the mechanisms underlying low activity of citrate synthase (CS) in A/J mice compared with other inbred strains of mice. Enzyme activity, protein content, and mRNA levels of CS were studied in the quadriceps muscles of A/J, BALB/cByJ, C57BL/6J, C3H/HeJ, DBA/2J, and PWD/PhJ strains of mice. Cytochrome c protein content was also measured. The results of the study indicate that A/J mice have a 50–65% reduction in CS activity compared with other strains despite similar levels of Cs mRNA and lack of differences in CS and cytochrome c protein content. CS from A/J mice also showed lower Michaelis constant ( Km) for both acetyl CoA and oxaloacetate compared with the other strains of mice. In silico analysis of the genomic sequence identified a nonsynonymous single nucleotide polymorphism (SNP) (rs29358506, H55N) in Cs gene occurring near the site of the protein interacting with acetyl CoA. Allelic variants of the polymorphism segregated with the catalytic properties of CS enzyme among the strains. In summary, H55N polymorphism in Cs could be the underlying cause of low CS activity and its high affinity for substrates in A/J mice compared with other strains. This SNP might also play a role in resistance to obesity of A/J mice.

Oyster citrate synthase: control of carbon entry into the Krebs cycle of a facultative anaerobe

1976 ◽  
Vol 54 (6) ◽  
pp. 892-895 ◽  
Author(s):  
J. H. A. Fields ◽  
P. W. Hochachka
Keyword(s):  
Enzyme Activity ◽  
Catalytic Activity ◽  
Crassostrea Gigas ◽  
Citrate Synthase ◽  
Specific Activity ◽  
Krebs Cycle ◽  
Adductor Muscle ◽  
Facultative Anaerobe ◽  
Wet Weight ◽  
Regulatory Properties

Citrate synthase (EC 4.1.3.7) in adductor muscle of the oyster, Crassostrea gigas, occurred in relatively low specific activity, about 1.5 μmol product formed per minute per gram wet weight of tissue. The enzyme activity was essentially independent of pH between pH 7.5 and 9.0. The Km values for acetyl-CoA and oxaloacetate were about 0.005 mM in each case. Catalytic activity was modulated by the adenylates, citrate, and 2-ketoglutarate, all of which were inhibitory. The regulatory properties of the enzyme suggest that during the transition to anoxia oxaloacetate becomes limiting, thus reducing flux through the initial stages of the Krebs cycle.

scholarly journals Energy metabolism and performance of Mytilus galloprovincialis under anaerobiosis

2007 ◽  
Vol 87 (4) ◽  
pp. 941-946 ◽  
Author(s):  
Jose M.F. Babarro ◽  
Uxío Labarta ◽  
María José Fernández Reiriz
Keyword(s):  
Energy Metabolism ◽  
Mytilus Galloprovincialis ◽  
Soft Tissues ◽  
Energy Charge ◽  
Fold Increase ◽  
Anaerobic Treatment ◽  
Strong Increase ◽  
Adenylate Energy Charge ◽  
Survival Potential ◽  
And Performance

Intertidal individuals of Mytilus galloprovincialis were exposed to anaerobiosis in laboratory at 22°C and a set of biochemical metabolites and survival potential determined. Differences in survival potential between individuals emersed or kept in oxygen-free seawater were residual according to ST50 values (survival time, P[asymp ]0.05) but emersed individuals survived significantly longer when considering ST90–100 values (P<0.05). Anaerobiosis was similarly activated under both emersion and incubation in anoxic seawater after 6 h according to a seven-fold increase in succinate. Longer exposure of individuals (up to 48 h) caused succinate (and propionate) to increase but in a higher magnitude under incubation with anoxic seawater. Propionate appeared in soft tissues after 24 h of incubation in anoxic seawater and after 48 h when individuals were emersed. Glycogen was not utilized after 6 h in any case, but was progressively used with longer exposure times and in a higher magnitude under incubation in anoxic seawater (48 h). Adenylate energy charge (AEC) was highly affected by both exposure time (P<0.001) and anaerobic treatment (P<0.01). Rapid breakdown of ATP and phospho-L-arginine (PLA) did occur during the first 24 h of anaerobiosis, the latter ATP drop was accompanied by slight increase of ADP but strong increase of AMP that accumulated in a higher magnitude under incubation in anoxic seawater. Biochemical results of the present study suggested a certain degree of aerobiosis for emersed M. galloprovincialis that in turn is linked to a slight but significant longer survival performance. Most significant biochemical changes occurred during the first 24 h of oxygen deprivation, but significant differences between treatments were observed after 24–48 h. These lag differences in biochemical metabolites together with more accurate survival analyses have to be considered when investigating the energy metabolism linked to the anaerobic performance of M. galloprovincialis.

scholarly journals An ‘in situ’ perfusion system suitable for investigating mammary-tissue metabolism in the lactating rat. Hormonal regulation of acetyl-CoA carboxylase

1988 ◽  
Vol 249 (3) ◽  
pp. 771-777 ◽  
Author(s):  
R A Clegg ◽  
D T Calvert
Keyword(s):  
Hormonal Regulation ◽  
Adenine Nucleotides ◽  
Energy Charge ◽  
Mammary Tissue ◽  
Adenylate Energy Charge ◽  
Acetyl Coa Carboxylase ◽  
Acetyl Coa ◽  
Tissue Samples ◽  
Control Tissue

A technique is described for the non-recirculating perfusion of inguinal/abdominal mammary tissue in situ in anaesthetized lactating rats. Tissue viability was maintained, without resort to infusion of vasoactive chemicals which may also be effectors of cellular metabolism, for at least 90 min. Total tissue adenine nucleotides (per mg of DNA) were somewhat decreased in perfused relative to non-perfused mammary tissue. DNA content (per g wet wt. of tissue) was diminished after 90 min of perfusion to approx. 65% of its value in control tissue. Adenylate energy-charge ratios were lower in perfused tissue in the absence of hormones than in control tissue. They were increased to control values by the presence of either insulin or isoprenaline in the perfusate. No changes occurred in flow rate of the perfusate that might account for these increases. In mammary tissue perfused without addition of hormones, acetyl-CoA carboxylase activities were similar to those measured in control tissue samples, although activity-ratio measurements implied some increase in the phosphorylation of this enzyme. Insulin or isoprenaline increased the activity of acetyl-CoA carboxylase, especially when this was measured at low concentrations of citrate. Confirming conclusions from previous experiments with mammary acini and explant preparations, insulin activated acetyl-CoA carboxylase in mammary tissue, but inhibition of its activity was not mediated by cyclic AMP.

Differential Contribution of Oxidative and Glycolytic Energy to Thrombin-Induced Platelet Functions

1979 ◽  
Vol 42 (02) ◽  
pp. 655-665 ◽  
Author(s):  
Bonro Kobayashi ◽  
Yasuko Watanabe ◽  
Naoyuki Takasugi ◽  
Makiko Kurita
Keyword(s):  
Oxidative Phosphorylation ◽  
Blood Platelets ◽  
Energy Charge ◽  
Krebs Cycle ◽  
Energy Condition ◽  
Pulse Labelling ◽  
Adenylate Energy Charge ◽  
Comparable Amount ◽  
Respiratory Inhibitors ◽  
Platelet Aggregates

SummaryWhen washed rabbit-blood platelets were preincubated in an artificial medium in the absence of external substrates, they aggregated in response to a low concentration of thrombin. The aggregation was completely inhibited after the preincubation with respiratory inhibitors. When glucose together with the respiratory inhibitors was added during the incubation, the aggregation was accelerated, whilst it was counteracted when Krebs-cycle substrates were added.ATP was generated actively during the incubation in the absence of external substrates, as well as in the presence of succinate. The ATP-generation was extremely inhibited by oligomycin. When glucose was added during the incubation with the respiratory inhibitor, the comparable amount of ATP with those in the oxidative systems was generated. Metabolic ADP was accumulated in the oxidative systems, particularly in the presence of succinate, in contrast to its low level in the glucose + oligomycin system. The results suggest that the counteraction of the aggregation by the Krebs-cycle substrate is attributed to the low adenylate energy charge. It is suggested that anaerobic glycolysis creates favorable energy condition for aggregation as compared with oxidative phosphorylation, although the washed platelets can be energized to a level above threshold of the aggregation when either one of the two energy generating systems is exerted.After the incubation of the platelets in the presence of thrombin, a higher level of metabolic ATP was observed under glycolytic condition, than under oxidative condition. Pulse-labelling experiments showed that ADP produced during the aggregation was rephosphorylated in a later part of the incubation in the glucose + KCN-fortified system. In the succinate-fortified system, the re-phosphorylation was very slow. The results suggest that oxidative phosphorylation is reduced in platelet aggregates treated with thrombin.

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