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1.
Tsaplina IA Krasil'nikova EN Zakharchuk LM Egorova MA Bogdanova TI Karavaĭko GI 《Mikrobiologiia》2000,69(3):334-340
The activities of carbon metabolism enzymes were determined in cellular extracts of the moderately thermophilic, chemolithotrophic, acidophilic bacterium Sulfobacillus thermosulfidooxidans subsp. asporogenes, strain 41, grown either at an atmospheric content of CO2 in the gas phase (autotrophically, heterotrophically, or mixotrophically) or autotrophically at a CO2 content increased to 5-10%. Regardless of the growth conditions, all TCA cycle enzymes (except for 2-oxoglutarate dehydrogenase), one glyoxylate cycle enzyme (malate synthase), and some carboxylases (ribulose bisphosphate carboxylase, pyruvate carboxylase, and phosphoenolpyruvate carboxylase) were detected in the cellular extracts of strain 41. During autotrophic cultivation of strains 41 and 1269, the increase in the CO2 content of the supplied air to 5-10% resulted in the activation of growth and iron oxidation, a 20-30% increase in the cellular content of protein, enhanced activity of the key TCA enzymes (citrate synthase and aconitase), and, in strain 41, a decrease in the activity of carboxylases. 相似文献
2.
Karavaiko G. I. Zakharchuk L. M. Bogdanova T. I. Egorova M. A. Tsaplina I. A. Krasil'nikova E. N. 《Microbiology》2002,71(6):651-656
To determine enzymatic activities in the thermotolerant strain K1 (formerly Sulfobacillus thermosulfidooxidans subsp. thermotolerans), it was grown in a mineral medium with (1) thiosulfate and Fe2+ or pyrite (autotrophic conditions), (2) Fe2+, thiosulfate, and yeast extract or glucose (mixotrophic conditions), and (3) yeast extract (heterotrophic conditions). Cells grown mixo-, hetero-, and autotrophically were found to contain enzymes of the tricarboxylic acid (TCA) cycle, as well as malate synthase, an enzyme of the glyoxylate cycle. Cells grown organotrophically in a medium with yeast extract exhibited the activity of the key enzymes of the Embden–Meyerhof–Parnas and Entner–Doudoroff pathways. The increased content of carbon dioxide (up to 5 vol %) in the auto- and mixotrophic media enhanced the activity of the enzymes involved in the terminal reactions of the TCA cycle and the enzymes of the pentose phosphate pathway. Carbon dioxide is fixed in the Calvin cycle. The highest activity of ribulose bisphosphate carboxylase was detected in cells grown autotrophically at the atmospheric content of CO2 in the air used for aeration of the growth medium. The activities of pyruvate carboxylase, phosphoenolpyruvate carboxylase, phosphoenolpyruvate carboxykinase, and phospho-enolpyruvate carboxytransphosphorylase decreased with increasing content of CO2 in the medium. 相似文献
3.
Chlorofluexus aurantiacus OK-70 fl was grown photoautotrophically with hydrogen as the electron source. The lowest doubling time observed was 26 h.The mechanism of CO2 fixation in autotrophically grown cells was studied. The presence of ribulose-1,5-bis-phosphate carboxylase and phosphoribulokinase could not be demonstrated. Carbon isotope fractionation (13C) was small, and alanine and aspartate but not 3-phosphoglycerate were the major labelled compounds in short term 14CO2 labelling. Thus CO2 is not fixed by the Calvin cycle.Fluoroacetate (FAc) completely inhibited protein synthesis in cultures and caused a slight citrate accumulation. However, CO2 fixation continued and increased polyglucose formation occurred. Under these conditions added acetate was metabolized to polyglucose, as were glycine, serine, glyoxylate and succinate, but to a lesser extent; little or no formate or CO was utilised.Glyoxylate inhibited CO2 fixation in vivo, indicating that pyruvate is formed from acetyl-CoA and CO2 by pyruvate synthase. Two key enzymes of the reductive TCA cycle, citrate lyase and -ketoglutarate synthase were not detected in cell free extracts, but pyruvate synthase and phosphoenolpyruvate carboxylase were demonstrated. It is concluded that acetyl-CoA is a central intermediate in the CO2 fixation process, but the mechanism of its synthesis is not clear.Abbreviations Rubisco
ribulose-1,5-bisphosphate carboxylase
- TCA cycle
tricarboxylic acid cycle
- FAc
monofluoroacetate
- PEP
phosphoenolpyruvate
- MV
methyl viologen
- TTC
triphenyltetrazolium chloride
- PMS
phenazine methosulfate 相似文献
4.
Earlier labeling experiments have shown that autotrophically grown Acetobacterium woodii assimilates cell carbon via direct acetyl CoA formation from 2 CO2, rather than via the Calvin cycle. Cell extracts contained the enzymes required for biosynthesis starting from acetyl CoA and CO2. Notably, pyruvate synthase, pyruvate phosphate dikinase, and phosphoenolpyruvate carboxytransphosphorylase were present in sufficiently high activities. Ribulose-1,5-bisphosphate carboxylase activity could not be detected. The observed enzyme pattern was consistent with the postulated biosynthetic pathway as deduced from 14C-labeling experiments. 相似文献
5.
S. A. Ensign Frederick J. Small Jeffrey R. Allen Miriam K. Sluis 《Archives of microbiology》1998,169(3):179-187
Short-chain aliphatic epoxides and ketones are two classes of toxic organic compounds formed biogenically and anthropogenically.
In spite of their toxicity, these compounds are utilized as primary carbon and energy sources or are generated as intermediate
metabolites in the metabolism of other compounds (e.g., alkenes, alkanes, and secondary alcohols) by a number of diverse bacteria.
One bacterium capable of using both classes of compounds is the gram-negative aerobe Xanthobacter strain Py2. Studies of epoxide and ketone (acetone) metabolism by Xanthobacter strain Py2 have revealed a central role for CO2 in these processes. Both classes of compounds are metabolized by carboxylation reactions that produce β-keto acids as products.
The epoxide- and ketone-converting enzymes are distinct carboxylases with molecular properties and cofactor requirements unprecedented
for other carboxylases. Epoxide carboxylase is a four-component multienzyme complex that requires NADPH and NAD+ as cofactors. In the course of epoxide carboxylation, a transhydrogenation reaction occurs wherein NADPH undergoes oxidation
and NAD+ undergoes reduction. Acetone carboxylase is a multimeric (three-subunit) ATP-dependent enzyme that forms AMP and inorganic
phosphate as ATP hydrolysis products in the course of acetone carboxylation. Recent studies have demonstrated that acetone
metabolism in diverse anaerobic bacteria (sulfate reducers, denitrifiers, phototrophs, and fermenters) also proceeds by carboxylation
reactions. ATP-dependent acetone carboxylase activity has been demonstrated in cell-free extracts of the anaerobic acetone-utilizers
Rhodobacter capsulatus, Rhodomicrobium vannielii, and Thiosphaera pantotropha. These studies have identified new roles for CO2 as a cosubstrate in the metabolism of two classes of important xenobiotic compounds. In addition, two new classes of carboxylases
have been identified, the investigation of which promises to reveal new insights into biological strategies for the fixation
of CO2 to organic substrates.
Received: 13 August 1997 / Accepted: 6 October 1997 相似文献
6.
Presence of Acetyl Coenzyme A (CoA) Carboxylase and Propionyl-CoA Carboxylase in Autotrophic Crenarchaeota and Indication for Operation of a 3-Hydroxypropionate Cycle in Autotrophic Carbon Fixation 总被引:2,自引:1,他引:1
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Castor Menendez Zsuzsa Bauer Harald Huber Nasser Gadon Karl-Otto Stetter Georg Fuchs 《Journal of bacteriology》1999,181(4):1088-1098
The pathway of autotrophic CO2 fixation was studied in the phototrophic bacterium Chloroflexus aurantiacus and in the aerobic thermoacidophilic archaeon Metallosphaera sedula. In both organisms, none of the key enzymes of the reductive pentose phosphate cycle, the reductive citric acid cycle, and the reductive acetyl coenzyme A (acetyl-CoA) pathway were detectable. However, cells contained the biotin-dependent acetyl-CoA carboxylase and propionyl-CoA carboxylase as well as phosphoenolpyruvate carboxylase. The specific enzyme activities of the carboxylases were high enough to explain the autotrophic growth rate via the 3-hydroxypropionate cycle. Extracts catalyzed the CO2-, MgATP-, and NADPH-dependent conversion of acetyl-CoA to 3-hydroxypropionate via malonyl-CoA and the conversion of this intermediate to succinate via propionyl-CoA. The labelled intermediates were detected in vitro with either 14CO2 or [14C]acetyl-CoA as precursor. These reactions are part of the 3-hydroxypropionate cycle, the autotrophic pathway proposed for C. aurantiacus. The investigation was extended to the autotrophic archaea Sulfolobus metallicus and Acidianus infernus, which showed acetyl-CoA and propionyl-CoA carboxylase activities in extracts of autotrophically grown cells. Acetyl-CoA carboxylase activity is unexpected in archaea since they do not contain fatty acids in their membranes. These aerobic archaea, as well as C. aurantiacus, were screened for biotin-containing proteins by the avidin-peroxidase test. They contained large amounts of a small biotin-carrying protein, which is most likely part of the acetyl-CoA and propionyl-CoA carboxylases. Other archaea reported to use one of the other known autotrophic pathways lacked such small biotin-containing proteins. These findings suggest that the aerobic autotrophic archaea M. sedula, S. metallicus, and A. infernus use a yet-to-be-defined 3-hydroxypropionate cycle for their autotrophic growth. Acetyl-CoA carboxylase and propionyl-CoA carboxylase are proposed to be the main CO2 fixation enzymes, and phosphoenolpyruvate carboxylase may have an anaplerotic function. The results also provide further support for the occurrence of the 3-hydroxypropionate cycle in C. aurantiacus. 相似文献
7.
Karavaĭko GI Zakharchuk LM Bogdanova TI Egorova MA Tsaplina IA Krasil'nikova EN 《Mikrobiologiia》2002,71(6):755-761
To determine enzymatic activities in the thermotolerant strain K1 (formerly "Sulfobacillus thermosulfidooxidans subsp. thermotolerans"), it was grown in a mineral medium with (1) thiosulfate and Fe2+ or pyrite (autotrophic conditions), (2) Fe2+, thiosulfate, and yeast extract or glucose (mixotrophic conditions), and (3) yeast extract (heterotrophic conditions). Cells grown mixo-, hetero-, and autotrophically were found to contain enzymes of the tricarboxylic acid (TCA) cycle, as well as malate synthase, an enzyme of the glyoxylate cycle. Cells grown organotrophically in a medium with yeast extract exhibited the activity of the key enzymes of the Embden-Meyerhof-Parnas and Entner-Doudoroff pathways. An increased content of carbon dioxide (up to 5 vol%) in the auto- and mixotrophic media enhanced the activity of the enzymes involved in the terminal reactions of the TCA cycle and the enzymes of the pentose phosphate pathway. Carbon dioxide was fixed in the Calvin cycle. The highest activity of ribulose bisphosphate carboxylase was detected in cells grown autotrophically at the atmospheric content of CO2 in the air used for aeration of the growth medium. The activities of pyruvate carboxylase, phosphoenolpyruvate carboxylase, phosphoenolpyruvate carboxykinase, and phosphoenolpyruvate carboxytransphosphorylase decreased with the increasing content of CO2 in the medium. 相似文献
8.
Masmoudi Raja Rival Alain Nato Aimé Lavergne Danièle Drira Nourredine Ducreux Georges 《Plant Cell, Tissue and Organ Culture》1999,57(2):139-143
While describing major trends of carbon metabolism during the initiation and expression of somatic embryogenesis in date palm
(Phoenix dactylifera L., cv. Deglet Nour), we have investigated the role of two carboxylases, namely PEPC (Phosphoenolpyruvate
carboxylase, EC 4.1.1.31) and RubisCO (Ribulose 1,5-bisphosphate carboxylase/oxygenase, EC 4.1.1.39), in embryogenic and non-embryogenic
cultures. The detection of PEPC activity on polyacrylamide native gels after electrophoresis revealed the presence of 3 active
isoforms in crude extracts from the embryogenic (E) callus strain, whereas only a single band was present in the non-embryogenic
(NE) one. The level of PEPC specific capacity was of the same order (3.9 ± 1.2 μmol CO2 h−1 mg−1 TSP) in both types of cultures. Further changes in carboxylase (PEPC and RubisCO) activities during the growth and development
of somatic embryo–derived plantlets were also analysed. The PEPC/RubisCO ratio was found to progressively decrease (from 17.7
to 0.2) throughout the in vitro development of plantlets, due to a substantial depletion of PEPC activity, which decreased
from 5.3 to 1.2 μmol CO2 h−1 mg−1 TSP. Concomitantly, RubisCO assumed greater importance (from 0.3 to 5.3 μmol CO2 h−1 mg−1
TSP
) and became the main route for inorganic carbon fixation. Western blot analysis using polyclonal antibodies raised against
PEPC and RubisCO purified from tobacco leaves confirmed this trend in terms of relative enzyme abundance.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
9.
Bjørnar Hassel 《Molecular neurobiology》2000,22(1-3):21-40
Anaplerosis, or de novo formation of intermediates of the tricarboxylic acid (TCA) cycle, compensates for losses of TCA cycle intermediates, especially
α-ketoglutarate, from brain cells. Loss of α-ketoglutarate occurs through release of glutamate and GABA from neurons and through
export of glutamine from glia, because these amino acids are α-ketoglutarate derivatives. Anaplerosis in the brain may involve
four different carboxylating enzymes: malic enzyme, phosphoenopyruvate carboxykinase (PEPCK), propionyl-CoA carboxylase, and
pyruvate carboxylase. Anaplerotic carboxylation was for many years thought to occur only in glia through pyruvate carboxylase;
therefore, loss of transmitter glutamate and GABA from neurons was thought to be compensated by uptake of glutamine from glia.
Recently, however, anaplerotic pyruvate carboxylation was demonstrated in glutamatergic neurons, meaning that these neurons
to some extent can maintain transmitter synthesis independently of glutamine. Malic enzyme, which may carboxylate pyruvate,
was recently detected in neurons. The available data suggest that neuronal and glial pyruvate carboxylation could operate
at as much as 30% and 40–60% of the TCA cycle rate, respectively. Cerebral carboxylation reactions are probably balanced by
decarboxylation reactions, because cerebral CO2 formation equals O2 consumption. The finding of pyruvate carboxylation in neurons entails a major revision of the concept of the glutamine cycle. 相似文献
10.
Pathways of autotrophic CO2 fixation and of dissimilatory nitrate reduction to N2O in Ferroglobus placidus 总被引:1,自引:0,他引:1
J. A. Vorholt Doris Hafenbradl Karl O. Stetter Rudolf K. Thauer 《Archives of microbiology》1997,167(1):19-23
The strictly anaerobic Archaeon Ferroglobus placidus was grown chemolithoautotrophically on H2 and nitrate and analyzed for enzymes and coenzymes possibly involved in autotrophic CO2 fixation. The following enzymes were found [values in parentheses = μmol min–1 (mg protein)–1]: formylmethanofuran dehydrogenase (0.2), formylmethanofuran:tetrahydromethanopterin formyltransferase (0.6), methenyltetrahydromethanopterin
cyclohydrolase (10), F420-dependent methylenetetrahydromethanopterin dehydrogenase (1.5), F420-dependent methylenetetrahydromethanopterin reductase (0.4), and carbon monoxide dehydrogenase (0.1). The cells contained
coenzyme F420 (0.4 nmol/mg protein), tetrahydromethanopterin (0.9 nmol/ mg protein), and cytochrome b (4 nmol/mg membrane protein). From the enzyme and coenzyme composition of the cells, we deduced that autotrophic CO2 fixation in F. placidus proceeds via the carbon monoxide dehydrogenase pathway as in autotrophically growing Archaeoglobus and Methanoarchaea species. Evidence is also presented that cell extracts of F. placidus catalyze the reduction of two molecules of nitrite to 1 N2O with NO as intermediate (0.1 μmol N2O formed per min and mg protein), showing that – at least in principle –F. placidus has a denitrifying capacity.
Received: 23 August 1996 / Accepted: 6 November 1996 相似文献
11.
Isolation and Characterization of Acetate-Utilizing Anaerobes from a Freshwater Sediment 总被引:1,自引:0,他引:1
Acetate-degrading anaerobic microorganisms in freshwater sediment were quantified by the most probable number technique. From
the highest dilutions a methanogenic, a sulfate-reducing, and a nitrate-reducing microorganism were isolated with acetate
as substrate. The methanogen (culture AMPB-Zg) was non-motile and rod-shaped with blunted ends (0.5–1 μm × 3–4 μm long). Doubling
times with acetate at 30–35°C were 5.6–8.1 days. The methanogen grew only on acetate. Analysis of the 16S rRNA sequence showed
that AMPB-Zg is closely related toMethanosaeta concilii. The isolated sulfate-reducing bacterium (strain ASRB-Zg) was rod-shaped with pointed ends (0.5–0.7 μm × 1.5–3.5 μm long),
weakly motile, spore forming, and gram positive. At the optimum growth temperature of 30°C the doubling times with acetate
were 3.9–5.3 days. The bacterium grew on a range of organic acids, such as acetate, butyrate, fumarate, and benzoate, but
did not grow autotrophically with H2, CO2, and sulfate. The closest relative of strain ASRB-Zg isDesulfotomaculum acetoxidans. The nitrate-reducing bacterium (strain ANRB-Zg) was rod-shaped (0.5–0.7 μm × 0.7–1 μm long), weakly motile, and gram negative.
Optimum growth with acetate occurred at 20–25°C. The bacterium grew on a range of organic substrates, such as acetate, butyrate,
lactate, and glucose, and did grow autotrophically with H2, CO2, and oxygen but not with nitrate. In the presence of acetate and nitrate, thiosulfate was oxidized to sulfate. Phylogenetically,
the closest relative of strain ANRB-Zg isVariovorax paradoxus. 相似文献
12.
Heliobacteria are a group of anoxygenic phototrophs that can grow photoheterotrophically in defined minimal media on only a limited range of organic substrates as carbon sources. In this study the mechanisms which operate to assimilate carbon and the routes employed for the biosynthesis of cellular intermediates were investigated in a newHeliobacterium strain, HY-3. This was achieved using two approaches (1) by measuring the activities of key enzymes in cell-free extracts and (2) by the use of13C nuclear magnetic resonance (NMR) spectroscopy to analyze in detail the labelling pattern of amino-acids of cells grown on [13C] pyruvate and [13C] acetate.Heliobacterium strain HY-3 was unable to grow autotrophically on CO2/H2 and neither (ATP)-citrate lyase nor ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBPcase) were detectable in cell-free extracts. The enzyme profile of pyruvate grown cells indicated the presence of a pyruvate:acceptor oxidoreductase at high specific activity which could convert pyruvate to acetyl-Coenzyme A. No pyridine nucleotide dependent pyruvate dehydrogenase complex activity was detected. Of the citric-acid cycle enzymes, malate dehydrogenase, fumarase, fumarate reductase and an NADP-specific isocitrate dehydrogenase were readily detectable but no aconitase or citrate synthase activity was found. However, the labelling pattern of glutamate in long-term 2-[13C] acetate incorporation experiments indicated that a mechanism exists for the conversion of carbon from acetyl-CoA into 2-oxoglutarate. A 2-oxoglutarate:acceptor oxidoreductase activity was present which was also assayable by isotope exchange, but no 2-oxoglutarate dehydrogenase complex activity could be detected. Heliobacteria appear to use a type of incomplete reductive carboxylic acid pathway for the conversion of pyruvate to 2-oxoglutarate but are unable to grow autotrophically using this metabolic route due to the absence of ATP-citrate lyase. 相似文献
13.
Melike Balk Farrakh Mehboob Antonie H. van Gelder W. Irene C. Rijpstra Jaap S. Sinninghe Damsté Alfons J. M. Stams 《Applied microbiology and biotechnology》2010,88(2):595-603
A mesophilic bacterium, strain An4, was isolated from an underground gas storage reservoir with methanol as substrate and
perchlorate as electron acceptor. Cells were Gram-negative, spore-forming, straight to curved rods, 0.5–0.8 μm in diameter,
and 2–8 μm in length, growing as single cells or in pairs. The cells grew optimally at 37°C, and the pH optimum was around
7. Strain An4 converted various alcohols, organic acids, fructose, acetoin, and H2/CO2 to acetate, usually as the only product. Succinate was decarboxylated to propionate. The isolate was able to respire with
(per)chlorate, nitrate, and CO2. The G+C content of the DNA was 42.6 mol%. Based on the 16S rRNA gene sequence analysis, strain An4 was most closely related
to Sporomusa ovata (98% similarity). The bacterium reduced perchlorate and chlorate completely to chloride. Key enzymes, perchlorate reductase
and chlorite dismutase, were detected in cell-free extracts. 相似文献
14.
Carlos E. Aragón Maritza Escalona Iris Capote Danilo Pina Inaudis Cejas Roberto Rodriguez Maria Jesus Cañal Jorge Sandoval Sophe Roels Pierre Debergh Justo Gonzalez-Olmedo 《In vitro cellular & developmental biology. Plant》2005,41(4):550-554
Summary The photosynthetic capacity changes and the main enzymatic systems related to carbon metabolism were investigated during the
in vitro culture of plantain shoots (Musa AAB cv. CEMSA 3/4) in temporary immersion bioreactors (TIB) and their subsequent acclimatization.
The maximal rate of photosynthesis (Pn), transpiration, and the activity of the carbon metabolism enzymes phosphoenolpyruvate
carboxylase (PEPC), acid invertase (AI), pyruvate kinase (PK) and sucrose phosphate synthase (SPS) were measured every 7 d
during the 21 d of elongation in TIB, and the following 42 d of acclimatization. Sucrose content in the liquid medium and
in the leaves was also determined. The most significant changes in plant growth were observed during acclimatization. During
the in vitro stage photosynthesis was limited (4–6 μmol CO2m−2s−1); the photosynthetic rate however increases rapidly and significantly as soon as in vitro culture is over during acclimatization. PEPC activity increased during the whole evaluation period. The highest levels were
achieved around days 42 and 56. PK and SPS activities were optimal during the first weeks in acclimatization (28–35 d), while
AI increased at the beginning of the elongation phase (7 d), and later at the end of the acclimatization (49–63 d). The relationships
between morphological parameters, photosynthetic capacity of the plantlets and the carbon metabolism enzymes during both phases
of the culture are discussed. 相似文献
15.
Hirotaka Shiba Toshiyuki Kawasumi Yasuo Igarashi Tohru Kodama Yasuji Minoda 《Archives of microbiology》1985,141(3):198-203
The incorporation of 14CO2 by the cell suspensions of an extremely thermophilic, aerobic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus was studied. After short time incubation of the cell suspensions with 14CO2, the radiactivity was initially present in aspartate, glutamate, succinate, phosphorylated compounds, citrate, malate and fumarate. All of these compounds except phosphorylated compounds were related to the members of the tricarboxylic acid cycle. The proportion of labelled aspartate onglutamate in total radioactivity on each chromatogram decreased with incubation time, while the percentage of the radioactivity incorporated in phosphorylated compounds increased with time up to 10 s. These indicated that aspartate and glutamate is derived from primary products of CO2 fixation.In cell-free extracts of Hydrogenobacter thermophilus, the two key enzymes in the Calvin cycle, ribulose-1,5-bisphosphate carboxylase and phosphoribulokinase could not be detected. The key enzymes of the reductive tricarboxylic acid cycle, fumarate reductase and ATP citrate lyase were present. Activities of phosphoenolpyruvate synthetase and pyruvate carboxylase were also detected. The referse reactions (dehydrogenase reactions) of -ketoglutarate synthase and pyruvate synthase could be detected by using methyl viologen as an electron acceptor.These findings strongly suggested that a new type of the reductive tricarboxylic acid cycle operated as the CO2 fixation pathway in Hydrogenobacter thermophilus. 相似文献
16.
The capacity to oxidize sulfide and the influence of the simultaneous presence of acetate in heterotrophically (acetate) and autotrophically (sulfide/CO2) grown Rhodopseudomonas capsulata was investigated.Sulfide oxidation of acetate-limited cultures was found inversely related to the specific growth rate. Upon acetate deprevation (metering pump stopped) increased rates of sulfide oxidation were observed. This points to the existence of a constitutive acceptor for the electrons from sulfide. It is suggested that a carrier functional in the light-induced cyclic electron flow operates as such. The rate of sulfide oxidation, however, is low when compared to autotrophically-grown cells. This is probably due to the low levels of Calvin cycle enzymes present in the acetate-grown cells.In cells growing on sulfide/CO2, the addition of acetate resulted in less sulfide being oxidized. Upon depletion of the acetate, the rate of sulfide oxidation again increased, however, insufficiently to maintain the accelerated growth rate. This indicates that under mixotrophic conditions the enzymes of the Calvin cycle are being synthesized to a far lesser extent.Non-Standurd Abbreviations PHB
poly--hydroxybutyric acid
- D
dilution rate
- TCA
Tri carboxylic acid cycle
- RubPcase
ribulose 1,5-bisphosphate carboxylase
- RP
reducing power 相似文献
17.
T. V. Finogenova N. V. Shishkanova I. T. Ermakova I. A. Kataeva 《Applied microbiology and biotechnology》1986,23(5):372-377
Summary Enzyme activities of the tricarboxylic acid (TCA) cycle and the anaplerotic pathways, as well as the cell cytology of two C. lipolytica mutants with the modified glyoxylate cycle and their parent strain were studied during the exponential growth phase on glucose or hexadecane.Among the TCA cycle enzymes, the key enzyme citrate synthase had the highest activity in all three strains grown on both substrates. NAD-dependent isocitrate dehydrogenase had the minimum activity. All strains had well-developed mitochondria.Pyruvate carboxylation was active in the wild strain and mutant 2 grown on glucose, where this reaction is the basic anaplerotic pathway for oxal-acetate synthesis; mutant 1 had actively functioning enzymes for both anaplerotic pathways — pyruvate carboxylase, isocitrate lyase and malate synthase.During hexadecane assimilation, the number of peroxisomes in all strains increased sharply, accompanied by a simultaneous increase in isocitrate lyase activity.The low activities of both isocitrate lyase and pyruvate carboxylase in mutant 2 give reason to believe that this strain has an additional pathway for oxalacetic acid synthesis during the assimilation of n-alkane. 相似文献
18.
Metabolite profiles and activities of key enzymes in the metabolism of organic acids, nitrogen and amino acids were compared
between chlorotic leaves and normal leaves of ‘Honeycrisp’ apple to understand how accumulation of non-structural carbohydrates
affects the metabolism of organic acids, nitrogen and amino acids. Excessive accumulation of non-structural carbohydrates
and much lower CO2 assimilation were found in chlorotic leaves than in normal leaves, confirming feedback inhibition of photosynthesis in chlorotic
leaves. Dark respiration and activities of several key enzymes in glycolysis and tricarboxylic acid (TCA) cycle, ATP-phosphofructokinase,
pyruvate kinase, citrate synthase, aconitase and isocitrate dehydrogenase were significantly higher in chlorotic leaves than
in normal leaves. However, concentrations of most organic acids including phosphoenolpyruvate (PEP), pyruvate, oxaloacetate,
2-oxoglutarate, malate and fumarate, and activities of key enzymes involved in the anapleurotic pathway including PEP carboxylase,
NAD-malate dehydrogenase and NAD-malic enzyme were significantly lower in chlorotic leaves than in normal leaves. Concentrations
of soluble proteins and most free amino acids were significantly lower in chlorotic leaves than in normal leaves. Activities
of key enzymes in nitrogen assimilation and amino acid synthesis, including nitrate reductase, glutamine synthetase, ferredoxin
and NADH-dependent glutamate synthase, and glutamate pyruvate transaminase were significantly lower in chlorotic leaves than
in normal leaves. It was concluded that, in response to excessive accumulation of non-structural carbohydrates, glycolysis
and TCA cycle were up-regulated to “consume” the excess carbon available, whereas the anapleurotic pathway, nitrogen assimilation
and amino acid synthesis were down-regulated to reduce the overall rate of amino acid and protein synthesis. 相似文献
19.
Günter Döhler 《Planta》1974,117(1):97-99
Summary The blue-green alga Anacystis nidulans (strain L 1402-1) was grown in air (0.03 vol. % CO2) and in 3.0 vol. % CO2 at +35° C. Levels of carbonic anhydrase were 3-fold higher in air-grown cells than in CO2-grown algae. CO2 content during growth has no effect on activity of RuDP carboxylase. Activities of PEP carboxylase, malic enzyme and catalase were higher in CO2-grown Anacystis cells. In air-grown cells higher activities of malate dehydrogenase, glycolate dehydrogenase, serine-pyruvate aminotransferase and aspartate--ketoglutarate aminotransferase were found. Levels of these enzymes are relatively low compared to those in green algae and higher plants. 相似文献
20.
Rhodobacter sphaeroides ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO)-deletion strain 16 was capable of photoheterotrophic growth with
acetate, while Rhodopseudomonas palustris RubisCO-deletion strain 2040 could not grow under these conditions. The reason for this difference lies in the fact that
Rba. sphaeroides and Rps. palustris use different pathways for acetate assimilation, the ethylmalonyl-CoA pathway, and glyoxylate-bypass cycle, respectively.
The ethylmalonyl-CoA pathway is distinct from the glyoxylate cycle as one molecule of CO2 and one molecule of HCO3
− per three molecules of acetyl-CoA are co-assimilated to form two malate molecules. The glyoxylate cycle directly converts
two acetyl-CoA molecules to malate. Each pathway, therefore, also dictates at what point, CO2 and reductant are consumed, thereby determining the requirement for the Calvin–Benson–Bassham reductive pentose phosphate
cycle. 相似文献