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1.
Yun Xia Duan Tao Chen Xun Chen Xue Ming Zhao 《Applied microbiology and biotechnology》2010,85(6):1907-1914
Carbon flow in Bacillus subtilis through the pentose phosphate (PP) pathway was modulated by overexpression of glucose-6-phosphate dehydrogenase (G6PDH) under
the control of the inducible Pxyl promoter in B. subtilis PY. Alteration of carbon flow into the PP pathway will affect the availability of ribulose-5-phosphate (Ru5P) and the riboflavin
yield. Overexpression of G6PDH resulted in the glucose consumption rate increasing slightly, while the specific growth rate
was unchanged. An improvement by 25% ± 2 of the riboflavin production was obtained. Compared to by-products formation in flask
culture, low acid production (acetate and pyruvate) and more acetoin were observed. Metabolic analysis, together with carbon
flux redistribution, indicated that the PP pathway fluxes are increased in response to overexpression of G6PDH. Moreover,
increased flux of the PP pathway is associated with an increased intracellular pool of Ru5P, which is a precursor for riboflavin
biosynthesis. The high concentrations of Ru5P could explain the increased riboflavin production. 相似文献
2.
A model of the C
3 photosynthetic system is developed which describes the sensitivity of the steadystate rate of carbon dioxide assimilation to changes in the activity of several enzymes of the system. The model requires measurements of the steady-state rate of carbon dioxide assimilation, the concentrations of several intermediates in the photosynthetic system, and the concentration of the active site of ribulose 1,5-bisphosphate carboxyalse/oxygenase (Rubisco). It is shown that in sunflowers (Helianthus annuus L.) at photon flux densities that are largely saturating for the rate of photosynthesis, the steady-stete rate of carbon dioxide assimilation is most sensitive to Rubisco activity and, to a lesser degree, to the activities of the stromal fructose, 6-bisphosphatase and the enzymes catalysing sucrose synthesis. The activities of sedoheptulose 1,7-bisphosphatase, ribulose 5-phosphate kinase, ATP synthase and the ADP-glucose pyrophosphorylase are calculated to have a negligible effect on the flux under the high-light conditions. The utility of this analysis in developing simpler models of photosynthesis is also discussed.Abbreviations
c
i
intercellular CO2 concentration
-
C
infP
supJ
control coefficient for enzyme P with respect to flux J
- DHAP
dihydroxyacetonephosphate
- E4P
erythrose 4-phosphate
- F6P
fructose 6-phosphate
- FBP
fructose 1,6-bisphosphate
- FBPase
fructose 1,6-bisphosphatase
- G3P
glyceraldehyde 3-phosphate
- G1P
glucose 1-phosphate
- G6P
glucose 6-phosphate
- Pi
inorganic phosphate
- PCR
photosynthetic carbon reduction
- PGA
3-phosphoglyceric acid
- PPFD
photosynthetically active photon flux density
-
R
n
J
response coefficient for effector n with respect to flux J
- R5P
ribose 5-phosphate
- Rubisco
ribulose 1,5-bisphosphate carboxylase/oxygenase
- Ru5P
ribulose 5-phosphate
- RuBP
ribulose 1,5-bisphosphate
- S7P
sedoheptulose 7-phosphate
- SBP
sedoheptulose 1,7-bisphosphate
- SBPase
sedoheptulose 1,7-bisphosphatase
- SPS
sucrose-phosphate synthase
- Xu5P
xylulose 5-phosphate
-
n
P
elasticity coefficient for effector n with respect to the catalytic velocity of enzyme P
This research was funded by an Australian Research Council grant to I.E.W. and was undertaken during a visity by K.A.M. to the James Cook University of North Queensland. The expert help of Glenys Hanley and Mick Kelly is greatly appreciated. 相似文献
3.
We have isolated several mutants ofSaccharomyces cerevisiae that are sensitive to oxidative stress in a screen for elevated sensitivity to hydrogen peroxide. Two of the sixteen complementation groups obtained correspond to structural genes encoding enzymes of the pentose phosphate pathway. Allelism of thepos10 mutation (POS forperoxidesensitivity) to thezwf1/met1 mutants in the structural gene for glucose 6-phosphate dehydrogenase was reported previously. The second mutation,pos18, was complemented by transformation with a yeast genomic library. The open reading frame of the isolated gene encodes 238 amino acids. No detectable ribulose 5-phosphate epimerase activity was found in thepos18 mutant, suggesting that the corresponding structural gene is affected in this mutant. For that reason the gene was renamedRPE1 (forribulose 5-phosphateepimerase).RPE1 was localized to chromosome X. The predicted protein has a molecular mass of 25 966 Daltons, a codon adaptation index (CAI) of 0.32, and an isoelectric point of 5.82. Database searches revealed 32 to 37% identity with ribulose 5-phosphate epimerases ofEscherichia coli, Rhodospirillum rubrum, Alcaligenes eutrophus andSolanum tuberosum. We have characterizedRPE1 by testing enzyme activities inrpe1 deletion mutants and in strains that overexpressRPE1, and compared the hydrogen peroxide sensitivity ofrpe1 mutants to that of other mutants in the pentose phosphate pathway. Interestingly, all mutants tested (glucose 6-phosphate dehydrogenase, gluconate 6-phosphate dehydrogenase, ribulose 5-phosphate epimerase, transketolase, transaldolase) are sensitive to hydrogen peroxide. 相似文献
4.
The production of α-ketoglutarate, adenine, thuringiensin production rate and thuringiensin yield on glucose consumed increased by 22%, 36%,
40% and 40%, respectively, in presence of 2 g citrate/l. However, citrate decreased pyruvate production, poly-β-hydroxybutyrate (PHB) production rate and PHB yield by 62%, 31% and 45%, respectively. The activities of pyruvate kinase
and glucose-6-phosphate dehydrogenase were 36%–45% lower and 50%–120% higher than those of the control, respectively. The
results suggest that citrate regulated the carbon flux to synthesis of adenine present in thuringiensin with a higher efficiency
of utilization of glucose by decreasing PHB synthesis. 相似文献
5.
Pachysolen tannophilus excreted riboflavin (12.7 m g/ml) into a synthetic medium withd-xylose as carbon source, when the pH was below 2.0. The addition of glucose enhanced the quantity of riboflavin excreted. The greatest riboflavin production was at pH 1.6 after 5 days at 30°C. 相似文献
6.
L. De Boer J. W. Brouwer C. W. Van Hassel P. R. Levering L. Dijkhuizen 《Antonie van Leeuwenhoek》1989,56(3):221-232
The metabolism of trimethylamine (TMA) and dimethylamine (DMA) in Arthrobacter P1 involved the enzymes TMA monooxygenase and trimethylamine-N-oxide (TMA-NO) demethylase, and DMA monooxygenase, respectively. The methylamine and formaldehyde produced were further metabolized via a primary amine oxidase and the ribulose monophosphate (RuMP) cycle. The amine oxidase showed activity with various aliphatic primary amines and benzylamine. The organism was able to use methylamine, ethylamine and propylamine as carbon-and nitrogen sources for growth. Butylamine and benzylamine only functioned as nitrogen sources. Growth on glucose with ethylamine, propylamine, butylamine and benzylamine resulted in accumulation of the respective aldehydes. In case of ethylamine and propylamine this was due to repression by glucose of the synthesis of the aldehyde dehydrogenase(s) required for their further metabolism. Growth on glucose/methylamine did not result in repression of the RuMP cycle enzyme hexulose-6-phosphate synthase (HPS). High levels of this enzyme were present in the cells and as a result formaldehyde did not accumulate. Ammonia assimilation in Arthrobacter P1 involved NADP-dependent glutamate dehydrogenase (GDH), NAD-dependent alanine dehydrogenase (ADH) and glutamine synthetase (GS) as key enzymes. In batch cultures both GDH and GS displayed highest levels during growth on acetate with methylamine as the nitrogen source. A further increase in the levels of GS, but not GDH, was observed under ammonia-limited growth conditions in continuous cultures with acetate or glucose as carbon sources.Abbreviations HPS
hexulose-6-phosphate synthase
- RuMP
ribulose monophosphate
- DMA
dimethylamine
- TMA
trimethylamine
- TMA-NO
trimethylamine-N-oxide
- ICL
isocitrate lyase
- GS
glutamine synthetase
- GDH
glutamate dehydrogenase
- ADH
alanine dehydrogenase
- GOGAT
glutamate synthase 相似文献
7.
In this work, a fundamental regulatory role of formate on thuringiensin production by resting cell of Bacillus thuringiensis YBT-032 was investigated. Nicotinamide adenine dinucleotide (NADH) production and formate dehydrogenase activity increased
with formate addition from 0.5 to 2.0 g/L, respectively. However, with the formate addition of 1.5 g/L, the activities of
pyruvate kinase and glucose 6-phosphate dehydrogenase reached a peak and increased by 316 and 150% relative to those of the
control, respectively. In addition, intracellular production of pyruvate, aspartate, citrate and adenine were significantly
enhanced by 75, 66, 32 and 78% as well. An improvement (90%) of thuringiensin production was also successfully obtained. Interestingly
to point out, thuringiensin yield was closely correlative with adenine production, and the linear relationship was also observed.
The results suggest that appropriate formate addition did act as a modulator and facilitate carbon flux in glycolysis and
pentose phosphate pathway to synthesize adenine and thuringiensin via intracellular NADH availability. 相似文献
8.
Phosphon-D (tributyl-2, 4-dichlorobenzylphosphonium chloride), known as an inhibitor of gibberellin biosynthesis, enhances photosynthetic electron transport by up to 200%, with Fe(CN)
6
3-
and NADP+ being the electron acceptors. Maximum stimulation is reached at phosphon-D concentrations around 2–5 M. At the same time photosynthetic ATP formation is gradually inhibited. Phosphon-D concentrations over 0.1 mM inhibit electron transport. The uncoupling activity of phosphon-D is manifested by inhibition of noncyclic ATP synthesis and by stimulation of light-induced electron flow. The inhibition of ATP synthesis drastically decreases photosynthetic carbon assimilation in a reconstituted spinach chloroplast system. The two ATP-dependent kinase reactions of the reductive pentose phosphate cycle become the rate-limiting steps. On the other hand a stimulated photoelectron transport increases the NADPH/NADP+ ratio, resulting in a drastic inhibition of chloroplast glucose-6-phosphate dehydrogenase (EC 1.1.1.49), the key enzyme of the oxidative pentose phosphate cycle. When light-induced electron flow is inhibited by high phosphon-D concentrations and the NADPH/NADP+ ratio is low, the light-dependent inhibition of glucose-6-phosphate dehydrogenase is gradually abolished.Abbreviations AMO-1618
2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidinecarboxylate methyl chloride
- B-Nine
N-dimethylaminosuccinamic acid
- CCC
(2-chloroethyl)-trimethylammonium chloride
- DCMU
3-(3,4-dichlorophenyl)-1, 1-dimethyl urea
- DCPIP
dichlorophenolindophenol
- G-6-PDH
glucose-6-phosphate dehydrogenase
- FBP
fructose bisphosphate
- F-6-P
fructose-6-phosphate
- 3-PGA
3-phosphoglyceric acid
- Posphon-D
tributyl-2,4-dichlorobenzylphosphonium chloride
- PMP
pentose monophosphates
- PPC
pentose phosphate cycle
- RuBP
ribulose bisphosphate
- Ru-5-P
ribulose-5-phosphate
Dedicated to Prof. Dr. Drs.h.c. Adolf Butenandt on the occasion of his 75. birthday 相似文献
9.
10.
M. V. Baev L. V. Chistoserdova B. M. Polanuer V. E. Sterkin M. Y. Kiriukhin Y. D. Tsygankov 《Archives of microbiology》1992,158(2):145-148
The ribulose monophosphate cycle methylotroph Methylobacillus flagellatum was grown under oxyturbidostat conditions on mixtures of methanol and formaldehyde. Formaldehyde when added at low concentration (50 mg/l) increased the methanol consumption and the yield of biomass. The presence of 150–300 mg/l of formaldehyde resulted in an increase of the growth rate from 0.74 to about 0.79–0.82 h-1. The presence of 500 mg/l of formaldehyde in the inflow decreased culture growth characteristics. Activities of methanol dehydrogenase and enzymes participating in formaldehyde oxidation and assimilation were measured. The enzymological profiles obtained are discussed.Abbreviations MDH
methanol dehydrogenase
- NAD-linked FDDH
NAD-linked formaldehyde dehydrogenase
- DLFDDH
dye-linked formaldehyde dehydrogenase
- DLFDH
dye-linked formate dehydrogenase
- GPDH
glucose-6-phosphate dehydrogenase
- PGDH
6-phosphogluconate dehydrogenase
- RuMP cycle
ribulose monophosphate cycle 相似文献
11.
Concentrations of m-Cl-peroxy benzoic acid (CPBA) higher than 0.1 mM decrease the ATP-content of Saccharomyces cerevisiae in the presence of glucose in 1 min to less than 10% of the initial value. In the absence of glucose, 1.0 mM CPBA is necessary for a similar effect. After the rapid loss of ATP in the first min in the presence of glucose caused by 0.2 mM CPBA, the ATP-content recovers to nearly the initial value after 10 min. Aerobic glucose consumption and ethanol formation from glucose are both completely inhibited by 1.0 mM CPBA. Assays of the activities of nine different enzymes of the glycolytic pathway as well as analysis of steady state concentrations of metabolites suggest that glyceraldehyde-3-phosphate dehydrogenase is the most sensitive enzyme of glucose fermentation. Phosphofructokinase and alcohol dehydrogenase are slightly less sensitive. Incubation for 1 or 10 min with concentrations of 0.05 to 0.5 mM CPBA causes a) inhibition of glyceraldehyde-3-phosphate dehydrogenase, b) decrease of the ATP-content and c) a decrease of the colony forming capacity. From these findings it is concluded that the disturbance of the ATP-producing glycolytic metabolism by inactivation of glyceraldehyde-3-phosphate dehydrogenase may be an explanation for cell death caused by CPBA.Abbreviations CPBA
m-Chloro-peroxy benzoic acid
- G-6-P
glucose-6-phosphate
- F-6-P
fructose-6-phosphate
- F-1,6-P2
frnctose-1,6-bisphosphate
- DAP
dihydroxyacetone phosphate
- GAP
glyceraldehyde-3-phosphate
- 2PGA
2-phosphoglycerate
- PEP
phosphoenol pyruvate
- Pyr
pyruvate
- EtOH
ethanol
- PFK
phosphofructokinase
- GAPDH
glyceraldehyde-3-phosphate dehydrogenase
- ADH
alcohol dehydrogenase
Dedicated to Prof. Dr. Wolfgang Gerok at the occasion of his 60th birthday 相似文献
12.
13.
The biosynthesis of one riboflavin molecule requires one molecule of GTP and two molecules of ribulose 5-phosphate as substrates. GTP is hydrolytically opened, converted into 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione by a sequence of deamination, side chain reduction and dephosphorylation. Condensation with 3,4-dihydroxy-2-butanone 4-phosphate obtained from ribulose 5-phosphate leads to 6,7-dimethyl-8-ribityllumazine. The final step in the biosynthesis of the vitamin involves the dismutation of 6,7-dimethyl-8-ribityllumazine catalyzed by riboflavin synthase. The mechanistically unusual reaction involves the transfer of a four-carbon fragment between two identical substrate molecules. The second product, 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione, is recycled in the biosynthetic pathway by 6,7-dimethyl-8-ribityllumazine synthase. This article will review structures and reaction mechanisms of riboflavin synthases and related proteins up to 2007 and 122 references are cited. 相似文献
14.
2-Ketogluconic acid and, to a lesser extent, gluconic acid were found to be major products of glucose catabolism by phosphate-limited cultures of Klebsiella aerogenes NCTC 418, and together accounted for up to 46% of the glucose carbon that was metabolized.Although the concentrations of both acids increased sub-stantially at low growth rates, their specific rates of synthesis decreased markedly, as did the proportion of glucose converted into these products.Determination of the affinity constant, for glucose, of phosphate-limited organisms showed it to be not significantly different from that of glucose-limited organisms (K
s
50 M), indicative of the phosphotransferase uptake system. And since these organisms possessed an active glucose 6-phosphate dehydrogenase, and had no detectable glucose dehydrogenase activity, it was concluded that gluconic acid and 2-ketogluconic acid arose from their corresponding phosphorylated metabolites, and not directly from glucose. 相似文献
15.
Hans-Martin Müller 《Archives of microbiology》1986,144(2):151-157
Batch cultures of Aspergillus niger grown from conidia on a medium with high C/N ratio accumulated gluconate from glucose with a yield of 57%. During almost the whole time of accumulation there was no net synthesis of total protein in the mycelium but the activity per flask and the specific activity of glucose oxidase (EC 1.1.3.4) in mycelial extracts increased whereas both values decreased for glucose dehydrogenase (EC 1.1.99.10) gluconate 6-phosphatase (cf. EC 3.1.3.1, 3.1.3.2), gluconokinase (EC 2.7.1.12), glucose 6-phosphate and phosphogluconate dehydrogenases (EC 1.1.1.49, EC 1.1.1.44), phosphoglucomutase (EC 2.7.5.1), and most enzymes of the Embden-Meyerhof pathway and the tricarboxylic acid cycle. Gluconate dehydratase (EC 4.2.1.39), gluconate dehydrogenase (EC 1.1.99.3) and enzymes of the Entner-Doudoroff pathway could not be detected. By cycloheximide the increase of glucose oxidase activity was inhibited. It is concluded that the high yield of gluconate was due mainly to the net (de novo) synthesis of glucose oxidase which occurred during protein turnover after the exhaustion of the nitrogen source, and which was not accompanied by a net synthesis of the other enzymes investigated. Some gluconate may also have been formed by hydrolytic cleavage of gluconate 6-phosphate.Abbreviations GOD
glucose oxidase
- GD
glucose dehydrogenase
- PP
pentose phosphate
- EM
Embden-Meyerhof
- TCA
tricarboxylic acid 相似文献
16.
为研究外源乙酸钠对大肠埃希菌DA19生长代谢的影响,将该菌株在氮源限制基本培养基及添加不同浓度乙酸钠的氮源限制基本培养基中连续培养,测定稳态时生长代谢参数和胞内关键酶酶活。与MN培养基相比,葡萄糖比消耗速率和延胡索酸比生成速率随外源乙酸钠质量浓度增加而逐渐下降,丙酮酸比生成速率则随外源乙酸钠质量浓度增加而明显增加,而乙酸比生成速率则明显降低(除9 g/L乙酸钠外)。磷酸果糖激酶、异柠檬酸脱氢酶、异柠檬酸裂解酶、苹果酸脱氢酶、磷酸烯醇式丙酮酸羧化酶和乙酸激酶酶活随外源乙酸钠质量浓度增加而呈先下降后上升的趋势,而6-磷酸葡萄糖脱氢酶则随着外源乙酸钠质量浓度增加而逐渐降低。为了应对外源乙酸钠压力,大肠埃希菌DA19的生长代谢和中心代谢途径酶活都发生了明显改变。 相似文献
17.
Subcellular distribution of enzymes of the oxidative pentose phosphate pathway in root and leaf tissues 总被引:13,自引:3,他引:10
The subcellular distribution of enzymes of the oxidative pentose phosphate
pathway was studied in plants. Root and leaf tissues from several species
were separated by differential centrifugation into plastidic and cytosolic
fractions. In all tissues studied, glucose 6-phosphate dehydrogenase and
6-phosphogluconate dehydrogenase were found in both plastidic and cytosolic
compartments. In maize and pea root, and spinach and pea leaf, the
non-oxidative enzymes of the pentose phosphate pathway (transaldolase,
transketolase, ribose 5-phosphate isomerase, ribulose 5-phosphate
3-epimerase) appear to be restricted to the plastid. In tobacco leaf and
root, however, the non-oxidative enzymes were found in the cytosolic as
well as the plastidic compartments. In the absence of ribose 5-phosphate
isomerase and ribulose 5-phosphate 3-epimerase in the cytosol, the product
of the oxidative limb of the pathway (ribulose 5-phosphate) must be
transported into a compartment capable of utilizing it. Ribulose
5-phosphate was supplied to isolated intact pea root plastids and was shown
to be capable of supporting nitrite reduction. The kinetics of ribulose
5-phosphate-driven nitrite reduction in isolated pea root plastids
suggested that the metabolite was translocated across the plastid envelope
in a carrier-mediated transport process, indicating the presence of a
translocator capable of transporting pentose phosphates.Keywords:
Pentose phosphate, subcellular, plastid, ribulose 5-phosphate,
compartmentation
相似文献
18.
Two genes involved in central carbon metabolism were inactivated to modulate intracellular glucose 6-phosphate and to evaluate
its effects on xanthan production in wild-type Xanthomonas oryzae pv. oryzae. Upon the inactivation of the phosphogluconate dehydratase gene (edd), intracellular glucose 6-phosphate increased from 0.05 to 1.17 mmol/g (dry cell wt). This was accompanied by increased xanthan
production of up to 2.55 g/l (culture medium). In contrast, inactivation of 6-phosphogluconate dehydrogenase gene (gndA) did not influence intracellular glucose 6-phosphate nor xanthan production. The intracellular availability of glucose 6-phosphate
is proposed as a rate-limiting factor in xanthan production, and it may be possible to increases production of xanthan by
modulating the activities of enzymes in central carbon metabolism. 相似文献
19.
N. Arfman E. M. Watling W. Clement R. J. van Oosterwijk G. E. de Vries W. Harder M. M. Attwood L. Dijkhuizen 《Archives of microbiology》1989,152(3):280-288
The enzymology of methanol utilization in thermotolerant methylotrophic Bacillus strains was investigated. In all strains an immunologically related NAD-dependent methanol dehydrogenase was involved in the initial oxidation of methanol. In cells of Bacillus sp. C1 grown under methanol-limiting conditions this enzyme constituted a high percentage of total soluble protein. The methanol dehydrogenase from this organism was purified to homogeneity and characterized. In cell-free extracts the enzyme displayed biphasic kinetics towards methanol, with apparent K
m values of 3.8 and 166 mM. Carbon assimilation was by way of the fructose-1,6-bisphosphate aldolase cleavage and transketolase/transaldolase rearrangement variant of the RuMP cycle of formaldehyde fixation. The key enzymes of the RuMP cycle, hexulose-6-phosphate synthase (HPS) and hexulose-6-phosphate isomerase (HPI), were present at very high levels of activity. Failure of whole cells to oxidize formate, and the absence of formaldehyde-and formate dehydrogenases indicated the operation of a non-linear oxidation sequence for formaldehyde via HPS. A comparison of the levels of methanol dehydrogenase and HPS in cells of Bacillus sp. C1 grown on methanol and glucose suggested that the synthesis of these enzymes is not under coordinate control.Abbreviations RuMP
ribulose monophosphate
- HPS
hexulose-6-phosphate synthase
- HPI
hexulose-6-phosphate isomerase
- MDH
methanol dehydrogenase
- ADH
acohol dehydrogenase
- PQQ
pyrroloquinoline, quinone
- DTT
dithiothreitol
- NBT
nitrobluetetrazolium
- PMS
phenazine methosulphate
- DCPIP
dichlorophenol indophenol 相似文献
20.
When exponentially growing Saccharomyces cerevisiae was transferred from a normal high water activity growth medium (aw 0.997) to a medium containing 8% NaCl low water activity growth medium (aw 0.955), glycerol accumulation during the first eight hours of the adaptation was both retarded and greatly diminished in magnitude. Investigation of the underlying reasons for the slow onset of glycerol accumulation revealed that not only was overall glycerol production reduced by salt transfer, but also the rates of ethanol production and glucose consumption were reduced. Measurement of glycolytic intermediates revealed an accumulation of glucose-6-phosphate, fructose-6-phosphate, fructose 1,6 bisphosphate and phosphoenolpyruvate in S. cerevisiae 3 to 4 h after transfer to salt, suggesting that one or more glycolytic enzymes were inhibited. Potassium ions accumulated in S. cerevisiae after salt transfer and reached a maximum about 6 h after transfer, whereas the sodium ion content increased progressively during the adaptation period. The trehalose content also increased in adapting cells. It is suggested that inhibition of glycerol production during the initial period of adaptation could be due to either the inhibition of glycerol-3-phosphate dehydrogenase by increased cation content or the inhibitin of glycolysis, glycerol being produced glycolytically in S. cerevisiae. The increased accumulation of glycerol towards the end of the 8-h period suggests that the osmoregulatory response of S. cerevisiae involves complex sets of adjustments in which inhibition of glycerol-3-phosphate dehydrogenase must be relieved before glycerol functions as a major osmoregulator. 相似文献