共查询到20条相似文献,搜索用时 31 毫秒
1.
S Boubekeur N Camougrand O Bunoust M Rigoulet B Guérin 《European journal of biochemistry》2001,268(19):5057-5065
This work was undertaken to clarify the role of acetaldehyde dehydrogenases in Saccharomyces cerevisiae metabolism during growth on respiratory substrates. Until now, there has been little agreement concerning the ability of mutants deleted in gene ALD4, encoding mitochondrial acetaldehyde dehydrogenase, to grow on ethanol. Therefore we constructed mutants in two parental strains (YPH499 and W303-1a). Some differences appeared in the growth characteristics of mutants obtained from these two parental strains. For these experiments we used ethanol, pyruvate or lactate as substrates. Mitochondria can oxidize lactate into pyruvate using an ATP synthesis-coupled pathway. The ald4Delta mutant derived from the YPH499 strain failed to grow on ethanol, but growth was possible for the ald4Delta mutant derived from the W303-1a strain. The co-disruption of ALD4 and PDA1 (encoding subunit E1alpha of pyruvate dehydrogenase) prevented the growth on pyruvate for both strains but prevented growth on lactate only in the double mutant derived from the YPH499 strain, indicating that the mutation effects are strain-dependent. To understand these differences, we measured the enzyme content of these different strains. We found the following: (a) the activity of cytosolic acetaldehyde dehydrogenase in YPH499 was relatively low compared to the W303-1a strain; (b) it was possible to restore the growth of the mutant derived from YPH499 either by addition of acetate in the media or by introduction into this mutant of a multicopy plasmid carrying the ALD6 gene encoding cytosolic acetaldehyde dehydrogenase. Therefore, the lack of growth of the mutant derived from the YPH499 strain seemed to be related to the low activity of acetaldehyde oxidation. Therefore, when cultured on ethanol, the cytosolic acetaldehyde dehydrogenase can partially compensate for the lack of mitochondrial acetaldehyde dehydrogenase only when the activity of the cytosolic enzyme is sufficient. However, when cultured on pyruvate and in the absence of pyruvate dehydrogenase, the cytosolic acetaldehyde dehydrogenase cannot compensate for the lack of the mitochondrial enzyme because the mitochondrial form produces intramitochondrial NADH and consequently ATP through oxidative phosphorylation. 相似文献
2.
T. Karl A. J. Curtis T. N. Rosenstiel R. K. Monson & R. Fall 《Plant, cell & environment》2002,25(9):1121-1131
Emissions of acetaldehyde from tree leaves were investigated by proton‐transfer‐reaction mass spectrometry (PTR‐MS), a technique that allows simultaneous monitoring of different leaf volatiles, and confirmed by derivatization and high‐performance liquid chromatography analysis. Bursts of acetaldehyde were released by sycamore, aspen, cottonwood and maple leaves following light–dark transitions; isoprene emission served as a measure of chloroplastic processes. Acetaldehyde bursts were not accompanied by ethanol, but exposure of leaves to inhibitors of pyruvate transport or respiration, or anoxia, led to much larger releases of acetaldehyde, accompanied by ethanol under anoxic conditions. These same leaves have an oxidative pathway for ethanol present in the transpiration stream, resulting in acetaldehyde emissions that are inhibited in vivo by 4‐methylpyrazole, an alcohol dehydrogenase (Adh) inhibitor. Labelling of leaf volatiles with 13CO2 suggested that the pools of cytosolic pyruvate, the proposed precursor of acetaldehyde bursts, were derived from both recent photosynthesis and cytosolic carbon sources. We hypothesize that releases of acetaldehyde during light–dark transitions result from a pyruvate overflow mechanism controlled by cytosolic pyruvate levels and pyruvate decarboxylase activity. These results suggest that leaves of woody plants contribute reactive acetaldehyde to the atmosphere under different conditions: (1) metabolic states that promote the accumulation of cytosolic pyruvate, triggering the pyruvate decarboxylase reaction; and (2) leaf ethanol oxidation resulting from ethanol transported from anoxic tissues. 相似文献
3.
The physiology and biochemistry of Sarcina ventriculi was studied in order to determine adaptations made by the organism to changes in environmental pH. The organism altered carbon and electron flow from acetate, formate and ethanol production at neutral pH, to predominantly ethanol production at pH 3.0. Increased levels of pyruvate dehydrogenase (relative to pyruvate decarboxylase) and acetaldehyde dehydrogenase occurred when the organism was grown at neutral pH, indicating the predominance of carbon flux through the oxidative branch of the pathway for pyruvate metabolism. When the organism was grown at acid pH, there was a significant increase in pyruvate decarboxylase levels and a decrease in acetaldehyde dehydrogenase, causing flux through the non-oxidative branch of the pathway. CO2 reductase and formate dehydrogenase were not regulated as a function of growth pH. Pyruvate dehydrogenase possessed Michaelis-Menten kinetics for pyruvate with an apparent K
m of 2.5 mM, whereas pyruvate decarboxylase exhibited sigmoidal kinetics, with a S0.5 of 12.0 mM. Differences in total protein banding patterns from cells grown at pH extremes suggested that synthesis of pyruvate decarboxylase and other enzymes was in part responsible for metabolic regulation of the fermentation products formed. 相似文献
4.
Hasso v. Hugo Siegfried Schoberth Vijay K. Madan Gerhard Gottschalk 《Archives of microbiology》1972,87(3):189-202
Summary Four clostridial species (C. pasteurianum, C. butylicum, C. butyricum and C. tetanomorphum) grow on pyruvate. Two other species (C. roseum and C. rubrum) only ferment this compound; this is probably due to their inability to synthesize hexose phosphates from pyruvate (fructose-1,6-diphosphatase and pyruvate carboxylase are absent).The fermentation of pyruvate by the above clostridia yields acetate, carbon dioxide, hydrogen and small amounts of compounds more reduced than acetate. Hydrogen pressure increases the amount of ethanol, butanol and butyrate formed during the fermentation of pyruvate. Since C. roseum and C. rubrum contain a ferredoxin: NADP reductase it seems likely that NADPH2 is the coenzyme involved in ethanol formation. In accordance with this acetaldehyde and alcohol dehydrogenases exhibit activity with NADPH2.The glyceraldehyde-3-phosphate dehydrogenase of the clostridia under investigation is NAD specific and so is the -hydroxy-butyryl-CoA dehydrogenase with the exception of C. kluyveri.The specific activity of hydrogenase and the coenzyme specificity of NAD(P) reductase vary among the clostridial species. 相似文献
5.
Björn Peters Anja Junker Katharina Brauer Bernadette Mühlthaler David Kostner Markus Mientus Wolfgang Liebl Armin Ehrenreich 《Applied microbiology and biotechnology》2013,97(6):2521-2530
Gluconobacter oxydans, a biotechnologically relevant species which incompletely oxidizes a large variety of carbohydrates, alcohols, and related compounds, contains a gene for pyruvate decarboxylase (PDC). This enzyme is found only in very few species of bacteria where it is normally involved in anaerobic ethanol formation via acetaldehyde. In order to clarify the role of PDC in the strictly oxidative metabolism of acetic acid bacteria, we developed a markerless in-frame deletion system for strain G. oxydans 621H which uses 5-fluorouracil together with a plasmid-encoded uracil phosphoribosyltransferase as counter selection method and used this technique to delete the PDC gene (GOX1081) of G. oxydans 621H. The PDC deletion mutant accumulated large amounts of pyruvate but almost no acetate during growth on d-mannitol, d-fructose or in the presence of l-lactate. This suggested that in G. oxydans acetate formation occurs by decarboxylation of pyruvate and subsequent oxidation of acetaldehyde to acetate. This observation and the efficiency of the markerless deletion system were confirmed by constructing deletion mutants of two acetaldehyde dehydrogenases (GOX1122 and GOX2018) and of the acetyl-CoA-synthetase (GOX0412). Acetate formation during growth of these mutants on mannitol did not differ significantly from the wild-type strain. 相似文献
6.
Steven Biesterveld Marika D. Kok Cor Dijkema Alexander J. B. Zehnder Alfons J. M. Stams 《Archives of microbiology》1994,161(6):521-527
The xylose metabolism of Bacteroides xylanolyticus X5-1 was studied by determining specific enzyme activities in cell free extracts, by following 13C-label distribution patterns in growing cultures and by mass balance calculations. Enzyme activities of the pentose phosphate pathway and the Embden-Meyerhof-Parnas pathway were sufficiently high to account for in vivo xylose fermentation to pyruvate via a combination of these two pathways. Pyruvate was mainly oxidized to acetyl-CoA, CO2 and a reduced cofactor (ferredoxin). Part of the pyruvate was converted to acetyl-CoA and formate by means of a pyruvate-formate lyase. Acetyl-CoA was either converted to acetate by a combined action of phosphotransacetylase and acetate kinase or reduced to ethanol by an acetaldehyde dehydrogenase and an ethanol dehydrogenase. The latter two enzymes displayed both a NADH- and a NADPH-linked activity. Cofactor regeneration proceeded via a reduction of intermediates of the metabolism (i.e. acetyl-CoA and acetaldehyde) and via proton reduction. According to the deduced pathway about 2.5 mol ATP are generated per mol of xylose degraded.Abbreviations PPP
Pentose phosphate pathway
- PKP
phosphoketolase pathway 相似文献
7.
Underwood SA Zhou S Causey TB Yomano LP Shanmugam KT Ingram LO 《Applied and environmental microbiology》2002,68(12):6263-6272
The production of ethanol from xylose by ethanologenic Escherichia coli strain KO11 was improved by adding various medium supplements (acetate, pyruvate, and acetaldehyde) that prolonged the growth phase by increasing cell yield and volumetric productivity (approximately twofold). Although added pyruvate and acetaldehyde were rapidly metabolized, the benefit of these additives continued throughout fermentation. Both additives increased the levels of extracellular acetate through different mechanisms. Since acetate can be reversibly converted to acetyl coenzyme A (acetyl-CoA) by acetate kinase and phosphotransacetylase, the increase in cell yield caused by each of the three supplements is proposed to result from an increase in the pool of acetyl-CoA. A similar benefit was obtained by inactivation of acetate kinase (ackA), reducing the production of acetate (and ATP) and sparing acetyl-CoA for biosynthetic needs. Inactivation of native E. coli alcohol-aldehyde dehydrogenase (adhE), which uses acetyl-CoA as an electron acceptor, had no beneficial effect on growth, which was consistent with a minor role for this enzyme during ethanol production. Growth of KO11 on xylose appears to be limited by the partitioning of carbon skeletons into biosynthesis rather than the level of ATP. Changes in acetyl-CoA production and consumption provide a useful approach to modulate carbon partitioning. Together, these results demonstrate that xylose fermentation to ethanol can be improved in KO11 by redirecting small amounts of pyruvate away from fermentation products and into biosynthesis. Though negligible with respect to ethanol yield, these small changes in carbon partitioning reduced the time required to complete the fermentation of 9.1% xylose in 1% corn steep liquor medium from over 96 h to less than 72 h. 相似文献
8.
Grau FH 《Applied and environmental microbiology》1983,45(1):84-90
Anaerobically, Brochothrix thermosphacta fermented glucose primarily to l-lactate, acetate, formate, and ethanol. The ratio of these end products varied with growth conditions. Both the presence of acetate and formate and a pH below about 6 increased l-lactate production from glucose. Small amounts of butane-2,3-diol were also produced when the pH of the culture was low (=5.5) or when acetate was added to the growth medium. Radioactive label from [1-C]acetate was incorporated into ethanol and l-lactate, implying reversibility of pyruvate-formate lyase. In crude extracts, the following enzymes involved in pyruvate metabolism were demonstrated: lactate dehydrogenase, phosphotransacetylase, acetate kinase, acetaldehyde dehydrogenase (coenzyme A acetylating), ethanol dehydrogenase, pH 6 acetolactate-forming enzyme, and diacetyl (acetoin) reductase. The lactate dehydrogenase did not require fructose-1,6-disphosphate or Mn for activity. 相似文献
9.
Considerable evidence indicates that acetaldehyde is released from the leaves of a variety of plants. The conventional explanation for this is that ethanol formed in the roots is transported to the leaves where it is converted to acetaldehyde by the alcohol dehydrogenase (ADH) found in the leaves. It is possible that acetaldehyde could also be formed in leaves by action of pyruvate decarboxylase (PDC), an enzyme with an uncertain metabolic role, which has been detected, but not characterized, in cottonwood leaves. We have found that leaf PDC is present in leaf veins and petioles, as well as in non-vein tissues. Veins and petioles contained measurable pyruvate concentrations in the range of 2 mM. The leaf vein form of the enzyme was purified approximately 143-fold, and, at the optimum pH of 5.6, the Km value for pyruvate was 42 μM. This Km is lower than the typical millimolar range seen for PDCs from other sources. The purified leaf PDC also decarboxylates 2-ketobutyric acid (Km = 2.2 mM). We conclude that there are several possible sources of acetaldehyde production in cottonwood leaves: the well-characterized root-derived ethanol oxidation by ADH in leaves, and the decarboxylation of pyruvate by PDC in leaf veins, petioles, and other leaf tissues. Significantly, the leaf vein form of PDC with its high affinity for pyruvate, could function to shunt pyruvate carbon to the pyruvate dehydrogenase by-pass and thus protect the metabolically active vascular bundle cells from the effects of oxygen deprivation. 相似文献
10.
Glucose and Pyruvate Metabolism of Spirochaeta litoralis, an Anaerobic Marine Spirochete 总被引:2,自引:1,他引:1
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The pathways of glucose and pyruvate metabolism in Spirochaeta litoralis, a free-living, strictly anaerobic marine spirochete, were studied. Addition of 0.2 to 0.4 M NaCl (final concentration) to suspending buffers prevented cell lysis and was necessary for gas evolution from various substrates by cell suspensions. The organism fermented glucose mainly to ethanol, acetate, CO(2), and H(2). Determination of radioactivity in products formed from (14)C-labeled glucose and assays of enzymatic activities in cell extracts indicated that S. litoralis catabolized glucose via the Embden-Meyerhof pathway. A clostridial-type clastic reaction was utilized by the spirochete to degrade pyruvate to acetyl-coenzyme A, CO(2), and H(2). Formation of acetate from acetyl-coenzyme A was catalyzed by phosphotransacetylase and acetate kinase. Nicotinamide adenine dinucleotide-dependent acetaldehyde and alcohol dehydrogenases converted acetyl-coenzyme A to ethanol. A reversible hydrogenase activity was detected in cell extracts. S. litoralis cell extracts contained a rubredoxin similar in spectral properties to other bacterial rubredoxins. 相似文献
11.
In isolated rat liver cells, ethanol inhibited gluconeogenesis from xylitol and sorbitol but not from fructose. Acetaldehyde, at initial concentrations of 0.2, 0.5, and 1.0 mm, stimulated gluconeogenesis from xylitol and sorbitol in the absence of pyrazole but inhibited in the presence of pyrazole. There was no effect with fructose. Acetate had no effect. Methylene blue and pyruvate (but not lactate) prevented the stimulatory as well as the inhibitory effects of acetaldehyde. Acetoacetate (but not β3-hydroxybutyrate) prevented, to a large extent, the inhibitory effects of low (but not high) concentrations of acetaldehyde. The inhibition by low concentrations of acetaldehyde appears to be mediated via acetaldehyde oxidation in the mitochondria, whereas the inhibition by high concentrations of acetaldehyde appears to reflect acetaldehyde oxidation in the cytosol. These data indicate that the inhibitory action of ethanol on glucose production from xylitol and sorbitol can be reproduced by physiological concentrations of acetaldehyde. Changes in the ratio produced during acetaldehyde metabolism appear to be responsible for these effects of acetaldehyde. These changes may contribute to the actions of ethanol on gluconeogenesis from these substrates. 相似文献
12.
Quintanilla ME Tampier L Sapag A Gerdtzen Z Israel Y 《American journal of physiology. Endocrinology and metabolism》2007,293(2):E531-E537
Individuals who carry the most active alcohol dehydrogenase (ADH) isoforms are protected against alcoholism. This work addresses the mechanism by which a high ADH activity leads to low ethanol intake in animals. Male and female ethanol drinker rats (UChB) were allowed access to 10% ethanol for 1 h. Females showed 70% higher hepatic ADH activity and displayed 60% lower voluntary ethanol intake than males. Following ethanol administration (1 g/kg ip), females generated a transient blood acetaldehyde increase ("burst") with levels that were 2.5-fold greater than in males (P < 0.02). Castration of males led to 1) an increased ADH activity (+50%, P < 0.001), 2) the appearance of an acetaldehyde burst (3- to 4-fold vs. sham), and 3) a reduction of voluntary ethanol intake comparable with that of na?ve females. The ADH inhibitor 4-methylpyrazole blocked the appearance of arterial acetaldehyde and increased ethanol intake. Since the release of NADH from the ADH.NADH complex constitutes the rate-limiting step of ADH (but not of ALDH2) activity, endogenous NADH oxidizing substrates present at the time of ethanol intake may contribute to the acetaldehyde burst. Sodium pyruvate given at the time of ethanol administration led to an abrupt acetaldehyde burst and a greatly reduced voluntary ethanol intake. Overall, a transient surge of arterial acetaldehyde occurs upon ethanol administration due to 1) high ADH levels and 2) available metabolites that can oxidize hepatic NADH. The acetaldehyde burst is strongly associated with a marked reduction in ethanol intake. 相似文献
13.
Desulfuromonas acetoxidans gen. nov. and sp. nov., a new anaerobic,sulfur-reducing,acetate-oxidizing bacterium 总被引:2,自引:0,他引:2
Anaerobic sea or fresh water media with acetate and elemental sulfur yielded enrichments of a new type of strictly anaerobic, rod-shaped, laterally flagellated, Gram-negative bacterium. Three pure culture-strains from different sulfide-containing sea water sources were characterized in detail and are described as a new genus and species Desulfuromonas acetoxidans.The new bacterium is unable to ferment organic substances; it obtains energy for growth by anaerobic sulfur respiration. Acetate, ethanol or propanol can serve as carbon and energy source for growth; their oxidation to CO2 is stoichiometrically linked to the reduction of elemental sulfur to sulfide. Organic disulfide compounds, malate or fumarate are the only other electron acceptors used. Butanol and pyruvate are used in the presence of malate only; no other organic compounds are utilized. Biotin is required as a growth factor. The following dry weight yields per mole of substrate are obtained: in the presence of sulfur: 4.21 g on acetate, 9.77 g on ethanol; in the presence of malate: 16.5 g on acetate, 34.2 g on ethanol and 46.2 g on pyruvate. Accumulations of cells are pink; cell suspensions exhibit absorption spectra resembling those of c-type cytochromes (abs. max. at 419, 523 and 553 nm). Malate-ethanol grown cells contain a b-type cytochrome in addition.In the presence of acetate, ethanol or propanol, Desulfuromonas strains form robust growing syntrophic mixed cultures with phototrophic green sulfur bacteria.Dedicated to Prof. Roger Y. Stanier on the occasion of his 60th barthday 相似文献
14.
The acs1 knockout mutant that has a disruption in the plastidic acetyl-coenzyme A (CoA) synthetase (ACS; At5g36880) gene was used to explore the role of this protein and plastidic acetate metabolism in Arabidopsis (Arabidopsis thaliana). Disruption of the ACS gene decreased ACS activity by 90% and largely blocked the incorporation of exogenous (14)C-acetate and (14)C-ethanol into fatty acids. Whereas the disruption had no significant effect on the synthesis of bulk seed triacylglycerols, the acs1 plants were smaller and flowered later. This suggests that the pyruvate dehydrogenase bypass provided by the aerobic fermentation pathway that converts pyruvate to acetate and probably on to fatty acids is important to the plants during normal growth. The role of ACS in destroying fermentative intermediates is supported by the increased sensitivity of the acs1 mutant to exogenous acetate, ethanol, and acetaldehyde compared to wild-type plants. Whereas these observations suggest that flux through the aerobic fermentation pathway is important, the reason for this flux is unclear. Interestingly, acetate is able to support high rates of plant growth on medium and this growth is blocked in the acs1 mutant. 相似文献
15.
Previous work showed that Methanobacillus omelianskii was a mixed culture of an ethanol-oxidizing organism called S organism and a hydrogen-utilizing methane bacterium, strain MOH. S organism grows poorly on ethanol unless a hydrogen-utilizing methanogenic bacterium is included to utilize the H(2) produced during growth. Further studies have shown that, among many substrates tested, only ethanol, n-propanol, n-butanol, isobutanol, n-pentanol, acetaldehyde, oxalacetate, and pyruvate are fermented by S organism, either alone or in combination with Methanobacterium ruminantium. It grew better in pure culture with pyruvate than with alcohols. H(2) gas phase inhibited growth on pyruvate as well as on alcohol. When grown alone on pyruvate, S organism produced mainly acetate, ethanol, and CO(2), in addition to a small amount of H(2). When combined with M. ruminantium, no H(2) and very little ethanol were produced and acetate production was increased. When M. ruminantium was present, electrons from pyruvate oxidation by S organism were channeled almost entirely to H(2) and hence to methane formation rather than ethanol. Also, S organism utilized more pyruvate when grown with M. ruminantium. Attempts to obtain better growth of S organism on ethanol by addition of many possible electron acceptors were unsuccessful. It grew best between 32 and 45 C, had a per cent guanine plus cytosine content of deoxyribonucleic acid bases of 47.27 +/- 0.1, contained no cytochrome, and could be grown on a defined medium with pyruvate as the energy and carbon source and with (NH(4))(2)SO(4) as the main nitrogen source. These and other results suggest that S organism belongs in a new genus, but assignment of a definite taxonomic status should await isolation and characterization of more strains. 相似文献
16.
The activity of NAD+ and NADP+-linked aldehyde dehydrogenases has been investigated in yeast cells grown under different conditions. As occurs in other dehydrogenase reactions the NAD(P)+-linked enzyme was strongly repressed in all hypoxic conditions; nervetheless, the NADP+-linked enzyme was active. The results suggest that the NAD(P)+ aldehyde dehydrogenase is involved in the oxidation of ethanol to acetyl-CoA, and that when the pyruvate dehydrogenase complex is repressed the NADP+-linked aldehyde dehydrogenase is operative as an alternative pathway from pyruvate to acetyl-CoA: pyruvate leads to acetaldehyde leads to acetate leads to acetyl-Coa. In these conditions the supply of NADPH is advantageous to the cellular economy for biosynthetic purposes. Short term adaptation experiments suggest that the regulation of the levels of the aldehyde dehydrogenase-NAD(P)+ takes place by the de novo synthesis of the enzyme. 相似文献
17.
Göran E. Nilsson 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1988,158(4):479-485
Summary In the final step of the pathway producing ethanol in anoxic crucian carp (Carassius carassius L.), acetaldehyde is reduced to ethanol by alcohol dehydrogenase. The presence of aldehyde dehydrogenase in the tissues responsible for ethanol production could cause an undesired oxidation of acetaldehyde to acetate coupled with a reduction of NAD+ to NADH. Moreover, acetaldehyde could competitively inhibit the oxidation of reactive biogenic aldehydes. In the present study, the distribution of aldehyde dehydrogenase (measured with a biogenic aldehyde) and alcohol dehydrogenase (measured with acetaldehyde) were studied in organs of crucian carp, common carp (Cyprinus carpio L.), rainbow trout (Salmo gairdneri Richardson), and Norwegian rat (Rattus norvegicus Berkenhout). The results showed that alcohol dehydrogenase and aldehyde dehydrogenase activities were almost completely spatially separated in the crucian carp. These enzymes occurred together in the other three vertebrates. In the crucian carp, alcohol dehydrogenase was only found in red and white skeletal muscle, while these tissues contained exceptionally low aldehyde dehydrogenase activities. Moreover, the low aldehyde dehydrogenase activity found in crucian carp red muscle was about 1000 times less sensitive to inhibition by acetaldehyde than that found in other tissues and other species. The results are interpreted as demonstrating adaptations to avoid a depletion of ethanol production, and possibly inhibition of biogenic aldehyde metabolism.Abbreviations
ADH
alcohol dehydrogenase
-
ALDH
aldehyde dehydrogenase
-
DOPAL
3,4-dihydroxyphenylacetaldehyde
-
MAO
monoamine oxidase
-
PCA
perchloric acid 相似文献
18.
Ethanol or acetaldehyde orally administered (15% and 2% respectively in drinking water) to male Wistar rats for three months induced alterations in the main liver enzymes responsible for ethanol metabolism, aspartate and alanine aminotransferases and NAD glutamate dehydrogenase. Ethanol produced a significant decrease in the activity of soluble alcohol dehydrogenase, while acetaldehyde induced alterations both in soluble and mitochondrial aldehyde dehydrogenases: soluble activity was significantly higher than in the control and ethanol-treated groups, and mitochondrial activity was significantly diminished. Both soluble aspartate and alanine aminotransferases showed pronounced increases by the chronic effect of acetaldehyde, while mitochondrial activities were practically unchanged by the effect of ethanol or acetaldehyde. Mitochondrial NAD glutamate dehydrogenase showed a rise in its activity both by the effect of chronic ethanol and acetaldehyde consumption. The level of metabolites assayed in liver extracts showed marked differences between ethanol and acetaldehyde treatment which indicates that ethanol produced a remarkable increase in glutamate, aspartate and free ammonia together with marked decrease in pyruvate and 2-oxoglutarate concentrations. Acetaldehyde consumption induced a significant decrease in 2-oxoglutarate and pyruvate concentrations. These observations suggest that ethanol has an important effect on the urea cycle enzymes, while the effect of acetaldehyde contributes to the impairment of the citric acid cycle. 相似文献
19.
Summary
Acetomonas oxydans is not able to grow on ethanol because of the lack of enzymes of the tricarboxylic acid cycle. Ethanol is merely oxidized to acetic acid.However, it was shown that Am. oxydans can utilize the energy from the oxidation of ethanol to acetic acid for growth. In this respect alcohol can be replaced by lactate.P/O ratios were measured with cell-free extracts and the following substrates: ethanol, lactate, pyruvate, acetaldehyde, NADH2 and NADPH2. The P/O values were identical when the cells were grown on the same medium. Glucose grown cells gave a P/O ratio for ethanol or lactate of 0.08. But with glucose-ethanol grown cells P/O ratios of 0.28 were obtained. Ethanol can be replaced by lactate for cell cultivation and as a substrate for the oxidative phosphorylation.In each oxidation step, i.e. ethanolacetaldehyde, lactatepyruvate, and acetaldehydeacetate, the same amount of ATP is produced per mole oxygen consumed when the cells were grown under comparable conditions. 相似文献
20.
Jardine K Barron-Gafford GA Norman JP Abrell L Monson RK Meyers KT Pavao-Zuckerman M Dontsova K Kleist E Werner C Huxman TE 《Photosynthesis research》2012,113(1-3):321-333
Green leaf volatiles (GLVs) are a diverse group of fatty acid-derived compounds emitted by all plants and are involved in a wide variety of developmental and stress-related biological functions. Recently, GLV emission bursts from leaves were reported following light–dark transitions and hypothesized to be related to the stress response while acetaldehyde bursts were hypothesized to be due to the ‘pyruvate overflow’ mechanism. In this study, branch emissions of GLVs and a group of oxygenated metabolites (acetaldehyde, ethanol, acetic acid, and acetone) derived from the pyruvate dehydrogenase (PDH) bypass pathway were quantified from mesquite plants following light–dark transitions using a coupled GC–MS, PTR-MS, and photosynthesis system. Within the first minute after darkening following a light period, large emission bursts of both C5 and C6 GLVs dominated by (Z)-3-hexen-1-yl acetate together with the PDH bypass metabolites are reported for the first time. We found that branches exposed to CO2-free air lacked significant GLV and PDH bypass bursts while O2-free atmospheres eliminated the GLV burst but stimulated the PDH bypass burst. A positive relationship was observed between photosynthetic activity prior to darkening and the magnitude of the GLV and PDH bursts. Photosynthesis under 13CO2 resulted in bursts with extensive labeling of acetaldehyde, ethanol, and the acetate but not the C6-alcohol moiety of (Z)-3-hexen-1-yl acetate. Our observations are consistent with (1) the “pyruvate overflow” mechanism with a fast turnover time (<1 h) as part of the PDH bypass pathway, which may contribute to the acetyl-CoA used for the acetate moiety of (Z)-3-hexen-1-yl acetate, and (2) a pool of fatty acids with a slow turnover time (>3 h) responsible for the C6 alcohol moiety of (Z)-3-hexen-1-yl acetate via the 13-lipoxygenase pathway. We conclude that our non-invasive method may provide a new valuable in vivo tool for studies of acetyl-CoA and fatty acid metabolism in plants at a variety of spatial scales. 相似文献