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1.
Changes in ribosephosphate isomerase and ribosephosphate pyrophosphokinase activities occurring in tobacco leaf tissues infected with the potato virus Y (PVY) were studied at the stage of acute infection. The results obtained have shown that during the entire experimental period the activities of both enzymes were at the end of a dark phase much higher in virus-infected tissues compared with the values found in healthy control plants. The courses of the activity curves of both enzymes were consistent and correlated with the reproduction curve of PVY. The results obtained suggest a direct involvement of both enzymes inde novo biosynthesis of the virus RNAvia the oxidative pentose phosphate pathway. 相似文献
2.
The content and changes in the activity of phosphogluconate dehydrogenase were followed in leaf tissues of tobacco plants
infected with the potato virus Y (PVY) in the acute phase of infection. The activity of the enzyme was higher in virus-infected
tissues during the entire experimental period compared with the values found in healthy control plants in both crude homogenate
and partially purified enzyme preparation. The courses of the activity curves of both the crude extract and partially purified
enzyme preparations were consistent and correlated with the reproduction curve of the virus. These results suggest that increased
activity of the enzyme was a result of its coarse regulation and indicate its immediate involvement in“de novo” biosynthesis of the virus via the oxidative pentose phosphate pathway. 相似文献
3.
L. Šindelár 《Biologia Plantarum》1986,28(6):440-448
The contents of NADP+, NADPH, changes in the activity of glucose-6-phosphate dehydrogenase and some questions relating to its regulation in leaf
tissues of tobacco plants infected with PVY were studied. The content of NADP+ and the total sum of pyridine nucleotides decreased after inoculation to 15 % and 30 %, respectively, whereas the content
of NADPH increased up to the threefold control value. The contents of NADP+, NADPH and Σ(NADPH + NADP+) linearly correlated with the reproduction curve of PVY. The value of the reduction charge RC and the value of the ratio
NADPH/NADP+ sharply increased after inoculation up to tenfold and eighteenfold values, respectively, of the healthy control.
The activity of glucose-6-phosphate dehydrogenase was markedly increased in virus-infected tissues during the entire experimental
period both in crude homogenate and after its partial purification when compared with the values found in healthy control
plants. The time courses of the activity curves of both crude and partially purified enzymes were coincident and correlated
with the reproduction curve of PVY. The results indicate the involvement of coarse regulation of the activity of the enzyme
by its content without the involvement of fine regulation by the ratio NADPH/NADP+ and RC. 相似文献
4.
Tobacco plants infected with the potato virus Y (PVY) were studied during the acute-infection period. The control enzymes of metabolic pathway of hosts RNA degradation tending to biosynthesis of PVY-RNA, its coarse/fine regulation and content of hosts RNA were monitored. Activities of ribonucleases, phosphomonoesterases and phosphodiesterases in both the crude homogenates and the partially purified enzyme preparations from the diseased leaves were markedly increased when compared to the tissues from healthy plants. The curves of enzyme activities positively correlated with the multiplication curve of the PVY and negatively correlated with the decreased contents of hosts RNA. The enzyme activity in homogenate samples did not significantly differ from the corresponding purified enzyme preparations. 相似文献
5.
N. J. Walesby I. A. Johnston 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1980,139(2):127-133
Summary Cold acclimation in fish is associated with an elevation in metabolic rate. The present study investigates the role of adenine nucleotides and related compounds in metabolic regulation following temperature acclimation. Brook trout (Salvelinus fontinalis) were acclimated for 10 weeks to either +4°C or +24°C. Both groups of fish were exercised at 2.5 body lengths s–1 for 2 weeks prior to sacrifice in order to control for differences in spontaneous activity.Concentrations of ATP, ADP, AMP, P
i
and PC were approximately 2-fold higher in white than red muscles. Temperature acclimation had little effect on total adenine nucleotide concentration in either muscle type. In white fibres acclimation to 4°C results in a 39% increase in [ADP] and [AMP], a 35% decrease in [PC] (phosphorylcreatine), and no significant change in [P
i
]. In contrast temperature has little effect on concentrations of these compounds in red muscle.Parameters of metabolic control — adenylate energy charge ([ATP]+0.5 [ADP]/[ATP]+[ADP]+[AMP]), phosphorylation state ([ATP]/[ADP]·[P
i
]), and the ratios [ATP][ADP] and [ATP][AMP] — were significantly lower in cold- than warm-acclimated white muscle. The observed changes in phosphorylation state and [ATP][AMP] are consistent with an increase in mitochondrial respiration and glycolysis, respectively.In conclusion, changes in metabolites may be an important factor in producing an enhanced metabolic rate in cold-acclimated fish. 相似文献
6.
Gerhard Wegener Nicholas M. Bolas André A. G. Thomas 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(3):247-256
Flight metabolism of locusts has been extensively studied, but biochemical and physiological methods have led to conflicting results. For this reason the non-invasive and non-destructive method of 31P NMR spectroscopy was used to study migratory locusts, Locusta migratoria, at rest and during flight.
Dedicated to Professor Dr. Ernst Zebe (University of Münster) on occasion of his 65th birthday. 相似文献
1. | In the flight muscle of resting locusts the ratio of phosphoarginine to ATP was the same whether determined by NMR (1.76) or biochemically, but the NMR-visible content of inorganic phosphate (Pi) was only 40% of ATP, i.e., much lower than total Pi as determined biochemically. This suggests that most of the Pi in flight muscle is not free, and hence not available as substrate or effector for cytosolic enzymes. Similarly, the free content of ADP and AMP in resting muscle was calculated to be much lower than the total content. |
2. | Flight brought about a marked increase in Pi and a decrease in phosphoarginine in flight muscle although there was no change in intracellular pH. |
3. | At the initiation of flight a new steady state of ATP, Pi, and phosphoarginine was rapidly established and minimal changes occurred after the first 2 s of flight. |
4. | From the free contents of ATP and phosphoarginine in working flight muscle the flight-induced fractional increases in free ADP and free AMP were calculated to be 5.0-fold and 27.4-fold, respectively. As Pi, ADP, and AMP are substrates and potent effectors of enzymes, the flight-induced increase in their contents is likely to have marked effects on metabolic flux in working muscle. |
5. | After short-term flight as well as prolonged flight, phosphoarginine, ATP, and Pi returned rapidly to their preflight levels, indicating that metabolic recovery from flight is rapid. |
6. | The locust appears to be an appropriate model for the study of metabolic regulation in aerobic muscle during exercise. |
7.
Vida Vambutas Walter Bertsch 《Biochemical and biophysical research communications》1976,73(3):686-693
Osmotically disrupted chloroplasts catalyze a rapid, light and AMP and ATP dependent 32Pi incorporation into ATP. Light does not stimulate [14C] AMP incorporation into ATP in this system. AMP in the presence of Pi inhibits electron flow in a manner analogous to ADP inhibition in the absence of Pi. The inhibition of AMP + Pi is reversed on addition of ADP. 相似文献
8.
1. The mitochondrial level of AMP gradually diminishes during incubation of mitochondria with glutamate but does not with succinate. This decline of AMP, associated with stoichiometric increase in ADP and/or ATP, is accelerated by the addition of electron acceptors or 2,4-dinitrophenol, while arsenite, arsenate and rotenone are inhibitory. These results are in agreement with the view that AMP is phosphorylated to ADP in the inner space of rat liver mitochondria via succinyl-CoA synthetase (succinate: CoA ligase (GDP), EC 6.2.1.4) and GTP:AMP phosphotransferase dependent on the oxidation of 2-oxoglutarate, which is promoted by the transfer of electron from NADH to the respiratory chain.2. Studies of the periodical changes of chemical quantities of adenine nucleotides as well as of their labelling with 32Pi reveals the following characteristics concerning mitochondrial phosphorylation. (i) In contrast to the mass action ratio of ATP to ADP, the ratio of ADP to AMP is not affected by the intramitochondrial concentration of Pi. (ii) 32Pi, externally added, is incorporated into ADP much more slowly than into γ-phosphate of ATP. (iii) Conversely, ATP loses its radioactivity from γ-phosphate position more rapidly than [32P]ADP when 32P-labelled mitochondria are incubated with non-radioactive Pi.3. In order to elucidate the above characteristic properties of phosphorylation, a hypothetical scheme is proposed which postulates the two separate compartments in the intramitochondrial pool of Pi; one readily communicates with external Pi and is utilized for the phosphorylation of ADP in oxidative phosphorylation, while the other less readily communicates with external Pi and serves as the precursor of ADP via succinyl-CoA synthetase and GTP:AMP phosphotransferase. 相似文献
9.
Effects of the superinfection with tobacco mosaic virus (TMV) on susceptible tobacco plants infected with potato virus Y (PVY)
were determined. Dynamic changes in the TMV and/or PVY contents, the ribonucleases (RNases), the phosphomonoesterase (PME),
the phosphodiesterase (PDE) and the glucose-6-phosphate dehydrogenase (G6P DH) activities were studied. The PVY infection
caused a substantial reduction in the multiplication of TMV. The content of TMV in the PVY inoculated leaves amounts to 6
and 9 % in the PVY systemically infected leaves when compared with single TMV. Surprisingly, the challenging virus (TMV) enhanced
the content of inducing virus (PVY) in the locally inoculated leaves up to 130 – 141 %. In contrast, the reduction of PVY
content down to 35 – 40 % by TMV was seen in the PVY systemically infected leaves. The activities of the RNase, the PME, the
PDE and the G6P DH were increased (when compared with the healthy plants) during the acute phase of single virus multiplication
(PVY or TMV). The increase in the activities of the enzymes in the leaves with mixed infection was at least as high as the
sum of the increases of single infections. Moreover, a higher increase than the sum was seen for G6P DH and PDE (by about
20 – 35 %).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
The influence of clofibrate on the glycolytic pathway in liver was studied. The changes in the activity of glucokinase and hexokinase were not significant. A reduction of phosphofructokinase (p less than 0.05) and pyruvate kinase activity was found (p less than 0.0005) during clofibrate feeding. An in vitro inhibition of these enzymes could not be demonstrated by clofibrate up to a concentration of 2.5 mM. Crossover plots of glycolytic intermediates indicate that the reduced pyruvate kinase activity may influence the glycolytic pathway in vivo. Clofibrate feeding induces a lower ATP:ADP ratio, a lower adenylate energy charge and elevates AMP levels in rat liver. This may possibly stimulate the hepatic glycogenolysis and the glucose utilisation by this organ. 相似文献
11.
R L Khandelwal 《Archives of biochemistry and biophysics》1978,191(2):764-773
The preincubation of rat liver crude extracts with ATP caused a 60% inactivation of phosphoprotein phosphatase in 30 min at 30 °C. The presence of Mg2+, or cyclic AMP, along with ATP in the preincubation mixture had no effect on the inactivation of phosphatase caused by ATP. The crude liver phosphatase was also inactivated by ADP or PPi; PPi being the most potent inactivating metabolite. AMP, adenosine or Pi were without any effect. The effect of ATP or PPi was completely reversed by cobalt. The cobalt effect was very specific and could not be replaced by several metal ions tested except by Mn2+ which was partly active. With the aid of sucrose density gradient studies, it was also shown that PPicauses an apparent conversion of a 4.1 S form to a 7.8 S form of the enzyme in rat liver extracts. Cobalt, on the other hand, converts the higher 7.8 S form to a lower 4.1 S form of the enzyme. The preincubation of purified rabbit liver phosphoprotein phosphatase with PPi also caused a complete inactivation of the enzyme in 40 min. The inactivation of the enzyme by PPi was completely reversed by cobalt. Unlike the apparent interconversion between different molecular forms of the enzyme by PPi and cobalt in rat liver crude extracts, no such interconversion of purified rabbit liver phosphoprotein phosphatase was observed in the presence of PPi and cobalt. 相似文献
12.
The ATP dipbosphohydrolase (EC 3.6.1.5) from pig pancreas hydrolyzes triphospho- and diphosphonucleosides. The reaction products of ATP hydrolysis are ADP, AMP and orthophosphate, but AMP accumulates at a faster rate than ADP. A time-course study showed a simultaneous breakdown of ATP and ADP with initial rates for ATP and ADP hydrolysis of 2.1 and 3.8μmol/min per mg protein, respectively. However, the rates reached similar values toward the end of the incubation period. According to double reciprocal plots and Dixon plots, the Km values for ATP and ADP are similar, Vmax for ADP hydrolysis is twice the Vmax for ATP hydrolysis and both nucleotides are competitive inhibitors of the other with their Ki values similar to their Km. These results are consistent with a sequential hydrolysis of the two diphosphoester bonds of ATP: ATP first binds to the enzyme, its γ-phosphate group is hydrolyzed and released, resulting in an enzyme-ADP complex which either breaks down to free enzyme and ADP or is further processed via hydrolysis of the β-phosphate group, releasing free enzyme, AMP and Pi. The experimental data showed that the processing step is favored. 相似文献
13.
Analysis of the energy metabolism after incubation of Saccharomyces cerevisiae with sulfite or nitrite 总被引:1,自引:0,他引:1
After addition of 5 mM sulfite or nitrite to glucose-metabolizing cells of Saccharomyces cerevisiae a rapid decrease of the ATP content and an inversely proportional increase in the level of inorganic phosphate was observed. The concentration of ADP shows only small and transient changes. Cells of the yeast mutant pet 936, lacking mitochondrial F1ATPase, after addition of 5 mM sulfite or nitrite exhibit changes in ATP, ADP and inorganic phosphate very similar to those observed in wild type cells. They key enzyme of glucose degradation, glyceraldehyde-3-phosphate dehydrogenase was previously shown to be the most sulfiteor nitrite-sensitive enzyme of the glycolytic pathway. This enzyme shows the same sensitivity to sulfite or nitrite in cells of the mutant pet 936 as in wild type cells. It is concluded that the effects of sulfite or nitrite on ATP, ADP and inorganic phosphate are the result of inhibition of glyceraldehyde-3-phosphate dehydrogenase and not of inhibition of phosphorylation processes in the mitochondria. Levels of GTP, UTP and CTP show parallel changes to ATP. This is explained by the presence of very active nucleoside monophosphate kinases which cause a rapid exchange between the nucleoside phosphates. The effects of the sudden inhibition of glucose degradation by sulfite or nitrite on levels of ATP, ADP and inorganic phosphate are discussed in terms of the theory of Lynen (1942) on compensating phosphorylation and dephosphorylation in steady state glucose metabolizing yeast.Abbreviations ATP
adenosine triphosphate
- ADP
adenosine diphosphate
- AMP
adenosine monophosphate
- Pi
inorganic orthophosphate
Dedicated to Prof. Dr. Hans Grisebach on the occasion of his sixtieth birthday 相似文献
14.
《Plant Physiology and Biochemistry》1999,37(3):195-201
The changes in the activity of glucose-6-phosphate dehydrogenase (G6PDH) (EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (6PGDH) (EC 1.1.1.44) in leaf tissues and the subcellular localisation of their isozymes in protoplasts derived from healthy and potato virus Y (PVY) infected plants of Nicotiana tabacum L. cv. Samsun were determined. The activities of G6PDH and 6PGDH were markedly increased in virus-infected leaves during the acute phase of infection both in crude homogenate and partial purificate (when compared with the values found in healthy control plants) and correlated with the multiplication curve of PVY. Intact chloroplasts and soluble cytosolic proteins were obtained from whole plants upon the culmination of the multiplication curve of PVY and upon the enhancement of the activity of both dehydrogenases by means of differential centrifugation of broken protoplasts. The chloroplastic fraction from infected protoplasts (based on chlorophyll content or NADP+-triosephosphate dehydrogenase activity) showed an enhanced activity of G6PDH (1.81 times that of healthy protoplasts), and 6PGDH (1.77 times). Cytosol from infected protoplasts (based on phosphoenolpyruvate carboxylase activity) contained only slightly enhanced activities of G6PDH and 6PGDH (only 1.26 and 1.16 times, respectively). 相似文献
15.
Byung-Chang Suh Jin H. Son Tong H. Joh Kyong-Tai Kim 《Journal of neurochemistry》1997,68(4):1622-1632
Abstract: We found that extracellular ATP can increase the intracellular Ca2+ concentration ([Ca2+]i) in mouse pineal gland tumor (PGT-β) cells. Studies of the [Ca2+]i rise using nucleotides and ATP analogues established the following potency order: ATP, adenosine 5′-O-(3-thiotriphosphate) ≥ UTP > 2-chloro-ATP > 3′-O-(4-benzoyl)benzoyl ATP, GTP ≥ 2-methylthio ATP, adenosine 5′-O-(2-thiodiphosphate) (ADPβS) > CTP. AMP, adenosine, α,β-methyleneadenosine 5′-triphosphate, β,γ-methyleneadenosine 5′-triphosphate, and UMP had little or no effect on the [Ca2+]i rise. Raising the extracellular Mg2+ concentration to 10 mM decreases the ATP-and UTP-induced [Ca2+]i rise, because the responses depend on the ATP4? and UTP4? concentrations, respectively. The P2U purinoceptor-selective agonist UTP and the P2Y purinoceptor-selective agonist ADPβS induce inositol 1,4,5-trisphosphate generation in a concentration-dependent manner with maximal effective concentrations of ~100 µM. In sequential stimulation, UTP and ADPβS do not interfere with each other in raising the [Ca2+]i. Costimulation with UTP and ADPβS results in additive inositol 1,4,5-trisphosphate generation to a similar extent as is achieved with ATP alone. Pretreatment with pertussis toxin inhibits the action of UTP and ATP by maximally 45–55%, whereas it has no effect on the ADPβS response. Treatment with 1 µM phorbol 12-myristate 13-acetate inhibits the ADPβS-induced [Ca2+]i rise more effectively than the ATP- and UTP-induced responses. These results suggest that P2U and P2Y purinoceptors coexist on PGT-β cells and that both receptors are linked to phospholipase C. 相似文献
16.
Entamoeba histolytica, an amitochondriate protozoan parasite that relies on glycolysis as a key pathway for ATP generation, has developed a unique extended PPi-dependent glycolytic pathway in which ADP-forming acetyl-coenzyme A (CoA) synthetase (ACD; acetate:CoA ligase [ADP-forming]; EC 6.2.1.13) converts acetyl-CoA to acetate to produce additional ATP and recycle CoA. We characterized the recombinant E. histolytica ACD and found that the enzyme is bidirectional, allowing it to potentially play a role in ATP production or in utilization of acetate. In the acetate-forming direction, acetyl-CoA was the preferred substrate and propionyl-CoA was used with lower efficiency. In the acetyl-CoA-forming direction, acetate was the preferred substrate, with a lower efficiency observed with propionate. The enzyme can utilize both ADP/ATP and GDP/GTP in the respective directions of the reaction. ATP and PPi were found to inhibit the acetate-forming direction of the reaction, with 50% inhibitory concentrations of 0.81 ± 0.17 mM (mean ± standard deviation) and 0.75 ± 0.20 mM, respectively, which are both in the range of their physiological concentrations. ATP and PPi displayed mixed inhibition versus each of the three substrates, acetyl-CoA, ADP, and phosphate. This is the first example of regulation of ACD enzymatic activity, and possible roles for this regulation are discussed. 相似文献
17.
Kernel abortion in maize : I. Carbohydrate concentration patterns and Acid invertase activity of maize kernels induced to abort in vitro 总被引:6,自引:4,他引:2
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The distribution of the glycolytic enzymes, phosphofructokinase, aldolase, triosephosphate isomerase, phosphoglycerate kinase, pyruvate kinase, and the oxidative pentose phosphate pathway enzymes, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, was determined in the leaf tissues of two C3-plants, pea and leek, and two C4-plants, maize and sorghum. All enzymes examined were found in epidermal tissue. In pea, maize, and sorghum leaves, the specific activities of these enzymes were usually higher in the nonphotosynthetic epidermal tissue than in the photosynthetic tissues of the leaves. In leek leaves, which were etiolated, specific activities were similar in both epidermal and mesophyll tissue. The distribution of the rate limiting enzymes of glycolysis and the oxidative pentose phosphate pathways probably reflects the capacity of each tissue to generate NADH, NADPH, and ATP from the oxidation of glucose. This capacity appears to be greater in leaf tissues unable to generate reducing equivalents and ATP by photosynthesis, that is, in epidermal tissues and etiolated mesophyll tissue. 相似文献
18.
The ratio of activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase (G6P DH/6PG DH), and the contents of glucose-6-phosphate (G6P), 6-phosphogluconate (6PG) and fructose-6-phosphate (F6P) were studied at various stages of potato virus Y (PVY) multiplication in Nicotiana tabacum cv. Samsun. G6P DH/6PG DH increased through the experiment from 0.42 to 0.53 in leaves of healthy tobacco, and up to 0.59 in PVY systemically infected leaves. However, these ratios in the ruptured protoplast preparations, and the chloroplast and cytosol fractions of healthy protoplasts were similar to that from infected ones. The ratio lower than 1, found in the healthy and/or PVY- infected leaf tissues and in the infected protoplasts as well, confirms the assumption that G6P DH is the control enzyme of oxidative pentosephosphate pathway not only in the healthy but also in the infected plants. The contents of G6P, 6PG and F6P in the period of the highest PVY multiplication were strongly decreased (to 30 – 50 % when compared with control healthy leaves) and were negatively correlated with the G6P DH and 6PG DH activities. 相似文献
19.
J Rosing D J Smith C Kayalar P D Boyer 《Biochemical and biophysical research communications》1976,72(1):1-8
Measurements are reported on the source of the ADP and γ-phosphoryl moieties of the initial ATP formed when chloroplast thylakoid membranes are energized by an acid-base transition. Millisecond mixing and quenching experiments demonstrate that most or all of the initial ATP, formed in amounts considerably less than the amount of CF1-ATPase present, arises from medium ADP and medium Pi. With no or low amounts of added medium ADP, the tightly-bound ADP present in thylakoid membranes is released to the medium on energization, then subsequently forms ATP. These results rule out the possible conversion of the ADP tightly-bound to CF1-ATPase to tightly-bound ATP as a step in the main pathway of chloroplast phosphorylation. Less complete experiments indicate a similar behavior of tightly-bound ADP of submitochondrial particles. 相似文献
20.
The changes in the contents of cyclic AMP, cyclic GMP, ATP, ADP, AMP and fructose-2,6-bisphosphate that occur in the mantle tissue of the mussel Mytilus galloprovincialis Lmk were analysed with regard to the annual gametogenic cycle. Throughout 2 years, the lowest contents of AMP, ADP and ATP were detected during late winter-spring, whereas the maximum appeared in the autumn months. During the second year, fructose-2,6-bisphosphate and cAMP showed a very similar behaviour. The levels of both compounds rose throughout the year until a maximum in September. Their behaviour was also similar to that observed during the first year, but displaced in time. Both in 1998 and in 1999, the highest level of cGMP was detected during the spring-summer months. The results obtained suggest that the glycolytic pathway, with regard to the breeding cycle, might be regulated by fructose-2,6-bisphosphate and cyclic AMP through the activation of 6-phosphofructo-1-kinase, which is the main regulating enzyme of the glycolysis in mantle of M. galloprovincialis. 相似文献