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1.
《Redox report : communications in free radical research》2013,18(1-2):35-41
AbstractThe polyphenolic structure common to flavonoids enables them to donate electrons and exert anti-oxidant activity. Since the mitochondrial electron transport chain consists of a series of redox inter-mediates, the effect of flavonoids in a complex mixture of polyphenols, as well as related pure flavonoids, was evaluated on the rat liver mitochondrial electron transport chain. A French maritime pine bark extract (PBE), a complex mixture of polyphenols and related pure flavonoids, was able to reduce cytochrome c reversibly, possibly by donation of electrons to the iron of the heme group; the donated electrons can be utilized by cytochrome c oxidase. Among single flavonoids tested, (-)-epicatechin gallate had the greatest ability to reduce cytochrome c. In addition, PBE competitively inhibited electron chain activity in both whole mitochondria and submitochondrial particles. A 3.5-fold increase in the apparent Km value for succinate was calculated from reciprocal plots. Among the flavonoids tested, taxifolin and (-)-epicatechin gallate showed minor inhibitory effects, while (±)-catechin and (+)-epicatechin were ineffective. Activities of NADH-ubiquinone, succinate-ubiquinone, and ubiquinol-cytochrome c reductases were inhibited by low concentrations of PBE to a similar extent. However, inhibition of cytochrome c oxidase activity required 4-fold higher PBE concen-trations. These results suggest that flavonoids reduce cytochrome c and that PBE inhibits electron transport chain activity mainly through NADH-ubiquinone, succinate-ubiquinone, and ubiquinol-cytochrome c reductases. 相似文献
2.
Moini H Arroyo A Vaya J Packer L 《Redox report : communications in free radical research》1999,4(1-2):35-41
The polyphenolic structure common to flavonoids enables them to donate electrons and exert antioxidant activity. Since the mitochondrial electron transport chain consists of a series of redox intermediates, the effect of flavonoids in a complex mixture of polyphenols, as well as related pure flavonoids, was evaluated on the rat liver mitochondrial electron transport chain. A French maritime pine bark extract (PBE), a complex mixture of polyphenols and related pure flavonoids, was able to reduce cytochrome c reversibly, possibly by donation of electrons to the iron of the heme group; the donated electrons can be utilized by cytochrome c oxidase. Among single flavonoids tested, (-)-epicatechin gallate had the greatest ability to reduce cytochrome c. In addition, PBE competitively inhibited electron chain activity in both whole mitochondria and submitochondrial particles. A 3.5-fold increase in the apparent Km value for succinate was calculated from reciprocal plots. Among the flavonoids tested, taxifolin and (-)-epicatechin gallate showed minor inhibitory effects, while (+/-)-catechin and (+)-epicatechin were ineffective. Activities of NADH-ubiquinone, succinate-ubiquinone, and ubiquinol-cytochrome c reductases were inhibited by low concentrations of PBE to a similar extent. However, inhibition of cytochrome c oxidase activity required 4-fold higher PBE concentrations. These results suggest that flavonoids reduce cytochrome c and that PBE inhibits electron transport chain activity mainly through NADH-ubiquinone, succinate-ubiquinone, and ubiquinol-cytochrome c reductases. 相似文献
3.
Acclimation to long-term water deficit in the leaves of two sunflower hybrids: photosynthesis, electron transport and carbon metabolism 总被引:14,自引:1,他引:13
The influence of long-term water deficit on photosynthesis, electron
transport and carbon metabolism of sunflower leaves has been examined.
Water deficit was imposed from flower bud formation up to the stage of full
flowering in the field on two sunflower hybrids with different drought
tolerance. CO2 assimilation and stomatal conductance of the intact leaves,
determined at atmospheric CO2 and full sunlight (1500-2000 mol quanta m-2
s-1), decreased with water deficit. Maximum quantum
efficiency of PSII (Fy/Fm) and
relative quantum yield of PSII (II) determined under similar
experimental conditions, did not change significantly in severely stressed
leaves. The strong inhibition of the plateau region of the light response
curve, determined at high CO2 (5%) in water-deficient sunflower leaves,
indicates that photosynthesis is also limited by non-stomatal factors. The
decreased slope and the plateau of the CO2 response curves show that the
capacity of carboxylation and RuBP regeneration decreased in severely
stressed intact leaves. Rubisco specific activity decreased in severely
stressed leaves, but Rubisco content increased under prolonged drought. The
increase of Rubisco content was significantly higher in leaves of the
drought-tolerant sunflower hybrid indicating that a higher Rubisco content
could be one factor in conferring better acclimation and higher drought
tolerance. 相似文献
4.
Oxygen is critical to aerobic metabolism, but excessive oxygen (hyperoxia) causes cell injury and death. An oxygen-tolerant strain of HeLa cells, which proliferates even under 80% O2, termed "HeLa-80," was derived from wild-type HeLa cells ("HeLa-20") by selection for resistance to stepwise increases of oxygen partial pressure. Surprisingly, antioxidant defenses and susceptibility to oxidant-mediated killing do not differ between these two strains of HeLa cells. However, under both 20 and 80% O2, intracellular reactive oxygen species (ROS) production is significantly (approximately 2-fold) less in HeLa-80 cells. In both cell lines the source of ROS is evidently mitochondrial. Although HeLa-80 cells consume oxygen at the same rate as HeLa-20 cells, they consume less glucose and produce less lactic acid. Most importantly, the oxygen-tolerant HeLa-80 cells have significantly higher cytochrome c oxidase activity (approximately 2-fold), which may act to deplete upstream electron-rich intermediates responsible for ROS generation. Indeed, preferential inhibition of cytochrome c oxidase by treatment with n-methyl protoporphyrin (which selectively diminishes synthesis of heme a in cytochrome c oxidase) enhances ROS production and abrogates the oxygen tolerance of the HeLa-80 cells. Thus, it appears that the remarkable oxygen tolerance of these cells derives from tighter coupling of the electron transport chain. 相似文献
5.
Respiratory metabolism: glycolysis, the TCA cycle and mitochondrial electron transport 总被引:4,自引:0,他引:4
The respiratory pathways of glycolysis, the tricarboxylic acid (TCA) cycle and the mitochondrial electron transport chain are ubiquitous throughout nature. They are essential for both energy provision in heterotrophic cells and a wide range of other physiological functions. Although the series of enzymes and proteins that participate in these pathways have long been known, their regulation and control are much less well understood. Further complexity arises due to the extensive interaction among these pathways in particular, and also between cytosolic and mitochondrial metabolism in general. These interactions include those between mitochondrial function in the photosynthetic and photorespiratory processes, amino-acid biosynthesis and the regulation of cellular redox. Recently, a wide range of molecular and biochemical strategies have been adopted to elucidate the functional significance of these interactions. 相似文献
6.
7.
Low root temperature effects on soybean nitrogen metabolism and photosynthesis 总被引:10,自引:9,他引:1 下载免费PDF全文
Duke SH Schrader LE Henson CA Servaites JC Vogelzang RD Pendleton JW 《Plant physiology》1979,63(5):956-962
The influences of low root temperature on soybeans (Glycine max [L.] Merr. cv. Wells) were studied by germinating and maintaining plants at root temperatures of 13 and 20 C through maturity. At 42 days from the beginning of imbibition, 13 and 20 C plants were switched to 20 and 13 C, respectively. Plants were harvested after 63 days. Control plants (13 C) did not nodulate, whereas those switched to 20 C did and at harvest had C2H2 reduction rates of 0.2 micromoles per minute per plant. Rates of C2H2 reduction decreased rapidly in plants switched from 20 to 13 C; however, after 2 days, rates recovered to original levels (0.8 micromoles per minute per plant) and then began a slow decline until harvest. Arrhenius plots of C2H2 reduction by whole plants indicated a large increase in the energy of activation below the inflection at 15 C. Highest C2H2 reduction rates (1.6 micromoles per minute per plant) were at 58 days for the 20 C control. Root respiration rates followed much the same pattern as C2H2 reduction in the 20 C control and transferred plants. At harvest, roots from 13 C-treated plants had the highest activities for malate dehydrogenase, glutamate oxaloacetate transaminase, and phosphoenolpyruvate carboxylase. Roots from transferred plants had intermediate activities and those from the 20 C treatment the lowest activities. Newly formed nodules from plants switched from 13 to 20 C had much higher glutamate dehydrogenase than glutamine synthetase activity. 相似文献
8.
9.
Nitrogen (N) availability is widely known as a determinant of plant growth and respiration rate. However, less attention has
been paid to the effect of the type of N source (nitrate, nitrite or ammonium) on the respiratory system. This review summarizes
the latest findings on this topic, with an emphasis on the effect of ammonium and nitric oxide (NO) on the respiratory system,
and the physiological role of alternative oxidase (AOX). First, concentrated ammonium has been found to increase plant respiration
rate (ammonium-dependent respiratory increase, ARI). We will introduce two hypotheses to explain ARI, futile ammonium cycling
and excess reducing equivalents, and verify the validity of each hypothesis. We suggest that these two hypotheses are not
necessarily mutually exclusive. Second, gene expression of AOX is suppressed when N is predominately available as nitrate instead of ammonium. We will discuss possible signaling pathways
leading to this expression pattern. Third, while AOX expression is induced by NO, AOX activity itself is insensitive to NO.
In contrast, activity of cytochrome c oxidase (COX) is sensitive to NO. We outline the NO production pathway, focusing on nitrite-dependent NO production, and
discuss the physiological significance of the fact that AOX activity is insensitive to NO. Finally, this review aims to build
an integrated scheme of the respiratory response to the type of N source, considering leaves in high light conditions or hypoxic
roots. 相似文献
10.
11.
12.
Remedios Ramirez Abdullah Sener Willy J. Malaisse 《Molecular and cellular biochemistry》1995,142(1):43-48
The mitochondrial NADH/NAD+ ratio for free nucleotides in rat pancreatic islets was judged from the cell content in L-glutamate and L-alanine, 2-ketoglutarate and pyruvate, and NH
4
+
. At a physiological concentration of D-glucose, such a ratio averaged 9.6±1.1%. A rise in hexose concentrations, above a threshold value in excess of 5.6 mM, caused a rapid, sustained and rapidly reversible decrease in the mitochondrial NADH/NAD+ ratio. It is speculated that in the process of glucose-stimulated insulin release, the latter change participates in the coupling between metabolic and secretory events by favouring both the activity of key mitochondrial dehydrogenases and the translocation of Ca2+ from the mitochondria into the cytosol. 相似文献
13.
Salt stress effects on the photosynthetic electron transport chain in two chickpea lines differing in their salt stress tolerance 总被引:1,自引:0,他引:1
Nuran Çiçek Abdallah Oukarroum Reto J. Strasser Gert Schansker 《Photosynthesis research》2018,136(3):291-301
The main objective of this study was to evaluate the effects of salt stress on the photosynthetic electron transport chain using two chickpea lines (Cicer arietinum L.) differing in their salt stress tolerance at the germination stage (AKN 87 and AKN 290). Two weeks after sowing, seedlings were exposed to salt stress for 2 weeks and irrigated with 200 ml of 200 mM NaCl every 2 days. The polyphasic OJIP fluorescence transient and the 820-nm transmission kinetics (photosystem I) were used to evaluate the effects of salt stress on the functionality of the photosynthetic electron transport chain. It was observed that a signature for salt stress was a combination of a higher J step (VJ), a smaller IP amplitude, and little or no effect on the primary quantum yield of PSII (φPo). We observed for AKN 290 a shorter leaf life cycle, which may represent a mechanism to cope with salt stress. For severely salt-stressed leaves, an inhibition of electron flow between the PQ pool and P700 was found. The data also suggest that the properties of electron flow beyond PSI are affected by salt stress. 相似文献
14.
M. Geiger V. Haake F. Ludewig U. Sonnewald & M. Stitt 《Plant, cell & environment》1999,22(10):1177-1199
15.
Drought and high-temperature stresses have been extensively studied; however, little is known about their combined impact on plants. In the present study, we determined the photosynthetic gas exchange, chlorophyll fluorescence, nitrogen level, and lipid peroxidation of the leaves of a perennial grass (Leymus chinensis (Trin.) Tzvel.) subjected to three constant temperatures (23, 29 and 32°C), and five soil-moisture levels (75–80%, 60–65%, 50–55%, 35–40% and 25–30% of field capacity, respectively). High temperature significantly decreased plant biomass, leaf green area, leaf water potential, photosynthetic rate (A), maximal efficiency of PSII photochemistry (F
v/F
m), actual PSII efficiency (ΦPSII), the activities of nitrate reductase (NR; EC 1.6.6.1) and glutamine synthetase (GS; EC 6.3.1.2), but markedly increased the ratio of leaf area to leaf weight (SLA), endopeptidase (EP; EC 3.4.24.11) activity, and malondialdehyde (MDA) content, especially under severe water stress conditions. The A and F
v/F
m were significantly and positively correlated with leaf-soluble protein content, and the activities of NR and GS. However, both photosynthesis parameters were significantly and negatively correlated with EP activity and MDA content (P < 0.05). It is suggested that high temperature, combined with severe soil drought, might reduce the function of PSII, weaken nitrogen anabolism, strengthen protein catabolism, and provoke lipid peroxidation. The results also indicate that severe water stress might exacerbate the adverse effects of high temperature, and their combination might reduce the plant productivity and distribution range of L. chinensis in the future. 相似文献
16.
Bożena Szal Agata Jastrzębska Marek Kulka Karolina Leśniak Anna Podgórska Tiit Pärnik Hiie Ivanova Olav Keerberg Per Gardeström Anna M. Rychter 《Planta》2010,232(6):1371-1382
The MSC16 cucumber (Cucumis sativus L.) mitochondrial mutant was used to study the effect of mitochondrial dysfunction and disturbed subcellular redox state
on leaf day/night carbon and nitrogen metabolism. We have shown that the mitochondrial dysfunction in MSC16 plants had no
effect on photosynthetic CO2 assimilation, but the concentration of soluble carbohydrates and starch was higher in leaves of MSC16 plants. Impaired mitochondrial
respiratory chain activity was associated with the perturbation of mitochondrial TCA cycle manifested, e.g., by lowered decarboxylation
rate. Mitochondrial dysfunction in MSC16 plants had different influence on leaf cell metabolism under dark or light conditions.
In the dark, when the main mitochondrial function is the energy production, the altered activity of TCA cycle in mutated plants
was connected with the accumulation of pyruvate and TCA cycle intermediates (citrate and 2-OG). In the light, when TCA activity
is needed for synthesis of carbon skeletons required as the acceptors for NH4
+ assimilation, the concentration of pyruvate and TCA intermediates was tightly coupled with nitrate metabolism. Enhanced incorporation
of ammonium group into amino acids structures in mutated plants has resulted in decreased concentration of organic acids and
accumulation of Glu. 相似文献
17.
18.
Gonzalez E; Aparicio-Tejo P; Gordon A; Minchin F; Royuela M; Arrese-Igor C 《Journal of experimental botany》1998,49(327):1705-1714
Two experiments were carried out to investigate the effects of
water-deficit stress on carbon and nitrogen metabolism of Pisum
sativum nodules. In the first experiment, leaf w was
allowed to reach -1.0 MPa over a period of 14 d whilst in the second
experiment -1.5 MPa was reached during the same time period. Nodule
activities of phosphoenol pyruvate carboxylase, glutamine synthetase,
alkaline invertase, pyruvate decarboxylase, alcohol dehdyrogenase, uridine
pyro-phosphorylase, and malate dehydrogenase activities were not affected
by water-deficit stress. In the first experiment (-1.0 MPa), sucrose
synthase (SS), an enzyme which hydrolyses sucrose to support nodule
metabolism, declined by 50% in activity and about 25% in content, according
to Western immunoblot data. In the second experiment (-1.5 MPa), SS
activity decreased by 75% together with glutamate synthase and aspartate
aminotransferase which declined by 60% and 40%, respectively. Coincident
with the decline of these activities, a dramatic increase in the nodule
content of sucrose and a slight increase in the levels of total free amino
acids were found. It has been recently suggested that the decline in SS
activity and, therefore, a reduced potential to metabolize sucrose may be
an important factor contributing to the overall response of soybean nodules
to water stress. These results suggest that this observation may be also
correct for temperate legumes with indeterminate nodules. However, in this
latter case, the activity of some enzymes involved in nitrogen assimilation
(glutamate synthase and aspartate aminotransferase) were also affected by
water-deficit stress).Key words: Pisum sativum, water
stress, nitrogen metabolism, nodule metabolism, pea, sucrose synthase.
相似文献
19.
Addition of ammonia to Chlorella pyrenoidosa, respiring in the dark following a period of photosynthesis, causes a stimulation of the flow of carbon into the synthesis of amino acids similar to that observed upon addition of ammonia during photosynthesis. In both cases, this stimulation is due not only to the increased availability of NH4+ for reductive amination of -ketoglutarate to glutamate but is also due to stimulation of the rate of conversion of phosphoenolpyruvate to pyruvate. Addition of NH4+in the dark causes a large increase in the formation of 6-phosphogluconate, beyond the increase in 6-phosphogluconate already seen when the light is turned off. When the light is turned off, the level of starch begins to decrease, and the rate of this decrease is not changed by the subsequent addition of ammonia. In contrast, the level of sucrose becomes nearly constant when the light is turned off, but begins immediately to decline when ammonia is added. As observed before, the level of ATP drops temporarily when the light is turned off and then rises to a steady state similar to that seen in the light. Upon the addition of ammonia, a similar transient drop and re-establishment in the level of ATP is seen.
These and other reported results are discussed with respect to sites and mechanisms of light-dark metabolic regulation leading to increased flow of carbon from carbohydrate reserves into mitochondrial metabolism in the dark, and the sites and mechanisms by which ammonia affects the rate of this flow. 相似文献
20.
《Journal of Plant Interactions》2013,8(1):159-166
Abiotic stresses, including nitrogen stress (NS), can hamper photosynthesis and cause oxidative damage to plants. Upregulation of the antioxidative defense system and photosynthesis induced by exogenous glycinebetaine (GB) and humic acid (HA) can mitigate the inhibitory effects of NS on plants. In the present investigation, the beneficial effects of exogenously applied GB and HA were examined on growth, leaf N status, photosynthesis, lipid peroxidation, and activities of some key antioxidant enzymes in the seedlings of maize cv. Zhengdan 958 (ZD958) exposed to NS. NS caused a significant reduction in total dry matter of seedlings of ZD958, but both GB and HA proved effective in mitigating this inhibition, hence, the beneficial effects of GB being more pronounced than those of HA. NS led to a considerable decrease in leaf total N and endogenous GB contents, stomatal conductance (g s), net photosynthetic rate (P n), intercellular CO2 concentration (C i), and activities of two key C4 photosynthesis enzymes phosphoenolpyruvate carboxylase (PEPCase) and ribulose-1,5-bisphosphate carboxylase (RuBPCase) as well as of superoxide dismutase (SOD) and peroxidase (POD). This treatment caused an increase in lipid peroxidation, but showed no effect on POD activity. Exogenous application of varying doses of GB resulted in a decrease in lipid peroxidation and C i, and an increase in leaf total N and endogenous glycinebetaine (EGB) content, P n, and activities of RuBPCase, PEPCase, SOD, and catalase (CAT) under NS. In contrast, application of different doses of HA resulted in a decrease in lipid peroxidation, an increase in P n, g s, and C i as well as SOD, CAT, and POD activities without increasing leaf total N and EGB content, and enhanced RuBPCase and PEPCase activities. The present study suggests that exogenous application of GB and HA can induce tolerance in maize plants to NS, but through the regulation of different mechanisms. 相似文献