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1.
An improved procedure is described for the recovery and purification of the coenzyme A-synthesizing protein complex (CoA-SPC) of Saccharomyces cerevisiae (bakers' yeast). The molecular mass of the CoA-SPC, determined prior to and following its purification, is estimated by Sephacryl S-300 size exclusion chromatography to be between 375 000–400 000. Two previously unreported catalytic activities attributed to CoA-SPC have been identified. One of these is CoA-hydrolase activity which catalyzes the hydrolysis of CoA to form 3′,5′-ADP and 4′-phosphopantetheine, and the other is dephospho-CoA-pyrophosphorylase activity which catalyzesa reaction between 4′-phosphopantetheine and ATP to form dephospho-CoA. The dephospho-CoA then reacts with ATP, catalyzed by the dephospho-CoA-kinase. to reform CoA. This sequence of reactions, referred to as the CoA/4′-phosphopantethiene cycle, provides a mechanism by which the 4′-phosphopantetheine can be recycled to form CoA. Each turn of the cycle utilizes two mol of ATP and produces one mol of ADP, one mol of PPi, and one mol of 3′,5′-ADP. Other than the hydrolysis of CoA by CoA-SPC, the 4′-phosphopantetheine for the cycle apparently could be supplied by alternate sources. One alternate source may be the conventional pathway of CoA biosynthesis. Intact CoA-SPC has been separated into two segments. One segment is designated apo-CoA-SPC and the other segment is referred to as the 10 000–15 000 Mr subunit. The 5′-ADP-4′-pantothenic acid-synthetase, 5′-ADP-4′-pantothenylcysteine-synthetase, 5′-ADP-4′-pantothenylcysteine-decarboxylase, and CoA-hydrolase activities reside in the apo-CoA-SPC segment of CoA-SPC. Whereas the dephospho-CoA-kinase and the dephospho-CoA-pyrophosphorylase activities reside in the 10 000–15 000 Mr subunit. Thus, the 10 000–15 000 Mr subunit mimics the bifunctional enzyme complex that catalyzes the final two steps in the conventional pathway of CoA biosynthesis. 相似文献
2.
Edsel T. Bucovaz Stanley J. Tarnowski William C. Morrison Robert M. Macleod John C. Morrison Camellia M. Sobhy James L. Rhoades James E. Fryer Jubran M. Wakim Walter D. Whybrew 《Molecular and cellular biochemistry》1980,30(1):7-26
The coenzyme A-synthesizing protein complex (CoA-SPC) is a multienzyme complex of Saccharomyces cerevisiae (Bakers' yeast), which has a molecular weight in excess of 200,000 as determined by Sephadex G-200 column chromatography. This multienzyme complex, which is insoluble in the crude yeast cell lysate, has been purified 229-fold. A cellular component of the yeast cell lysate, referred to as t-Factor, with a molecular weight of 400-1000 and chloride ion are involved in the solubilization of CoA-SPC. The CoA-SPC requires L-cysteine, D-pantothenic acid and ATP as substrates. The terminal CoA-SPC-bound intermediate is dephospho-CoA, which is subsequently phosphorylated and released from the complex as CoA. The sequence of reactions for the synthesis of CoA by the CoA-SPC differs significantly from those previously proposed for other systems. It could be that the reaction sequence is unique for the yeast cell. 相似文献
3.
A. Lintunen L. Lindfors P. Kolari E. Juurola E. Nikinmaa T. H?ltt? 《Annals of botany》2014,114(8):1711-1718
MethodsCO2 efflux measurements were conducted during freezing experiments for saplings of three Scots pine (Pinus sylvestris) and three Norway spruce (Picea abies) trees under laboratory conditions, and the magnitudes of the freezing-related bursts of CO2 released from the stems were analysed using a previously published mechanistic model of CO2 production, storage, diffusion and efflux from a tree stem. The freezing-related bursts of CO2 released from a mature Scots pine tree growing in field conditions were also measured and analysed.ConclusionsAll gases dissolved in the xylem sap are not trapped within the ice in the stem during freezing, as has previously been assumed, thus adding a new dimension to the understanding of winter embolism formation. The conduit water volume not only determines the volume of bubbles formed during freezing, but also the efficiency of gas efflux out of the conduit during the freezing process. 相似文献
4.
Aims: This paper presents a research on the disinfection efficiency of inoculated textile swatches by compressed carbon dioxide, an environmental friendly way to disinfect textiles as opposed to the conventional laundering procedures using water. The disinfection efficiency was determined by using the following microbes inoculated on cotton test fabrics: Enterococcus faecium, Enterobacter aerogenes and Candida albicans. Methods and Results: The experiments were performed using the high pressure extraction device with a maximum pressure of 50 MPa and a small extraction vessel of 500 ml. Pure CO2 and CO2 with added disinfection agent or commercial detergent were used. The chosen disinfecting agent was hydrogen peroxide, a widespread disinfecting chemical. It was found that treatment with CO2 for 25 min at 5 MPa and 40°C (313K) and the addition of 4 ml of specific detergent per litre of CO2 assures at least a five log step reduction of Enterobacter aerogenes and C. albicans, whilst treatment at 50°C (323K) with CO2 for 25 min at 5 MPa is sufficient for at least a five log step reduction for Enterococcus faecium. It was also found that a 15‐min CO2 treatment at 7 MPa and 20°C (293K) was sufficient for the inactivation of the yeast C. albicans, whilst these conditions were not rigorous enough for the challenge bacteria. On the other hand, the labscale treatment with CO2 for 25 min at pressure 4 and 6 MPa with the addition of detergent or hydrogen peroxide only yields a log step reduction of up to 4 log steps, thus proving the slightly disinfective properties of the CO2 treatment with added agents, but not reaching efficient results as a 5 log step reduction was not reached. Conclusions: Addition of heat to the compressed CO2 treatment of textiles inoculated with microorganisms proved more effective than the addition of detergent or disinfectant with compressed CO2 treatment at temperature of 20°C. Significance and Impact of the Study: CO2 treatment of textiles is a promising ecological alternative dry‐cleaning method for the disinfection of medical textiles. 相似文献
5.
Eddy Martin 《Inorganica chimica acta》2010,363(1):275-278
Treatment of LiC6F5 with B(C6F5)3 in equal volumes of light petroleum and diethyl ether at low temperature followed by slow warming to room temperature precipitates a microcrystalline solid which dries under vacuum to a material with the composition [Li(OEt2)3][B(C6F5)4]. Crystallization from diethyl ether yields solvent dependent [Li(OEt2)4][B(C6F5)4], which has been crystallographically characterised. 相似文献
6.
Umetsu Mitsuo Wang Zheng-Yu Zhang Jun Ishii Takasada Uehara Kaku Inoko Yoji Kobayashi Masayuki Nozawa Tsunenori 《Photosynthesis research》1999,60(2-3):229-239
The change of absorption spectra has been measured during the drying process of (31 R)bacteriochlorophyll (BChl) c from diethyl ether, dichloromethane (CH2Cl2) and carbon tetrachloride (CCl4) solutions. Absorption maxima of the Qy(0–0) transition of BChl c appear at 659 nm in diethyl ether, 680 nm in CH2Cl2 and 710 nm in CCl4. All these peaks are red-shifted to about 740 nm with formation of solid high aggregates when the solutions are completely dried. Fourier transform infrared spectra of the three solid aggregates are almost identical. However, magnetic circular dichroism and circular dichroism spectra are different and can be explained in terms of variations in stacking size of the aggregates and molecular arrangement of BChl c. Small-angle X-ray diffraction has been observed only for the aggregates treated with CH2Cl2, and the same sample gave rise to highly resolved cross polarization/magic angle spinning 13C nuclear magnetic resonance spectrum. The results suggest that molecular ordering of the solid-state BChl c aggregates is highly dependent on the formation process which is largely determined by the solvent used. 相似文献
7.
Fluid dynamics of anaerobic fermentation 总被引:2,自引:0,他引:2
In beer fermentation, yeast cells are kept in suspension, despite their higher density, by natural agitation created by ascending CO2 bubbles. Yeast cells are unable to nucleate bubbles but instead release CO2 in a soluble form in such a way that the medium tends to become supersaturated. A higher concentration of yeast cells and the presence of solid particles cause the formation of bubbles at the bottom of the fermenter and practically only there. The rising bubbles grow and accelerate by sweeping the CO2 formed throughout the fermenter by the suspended yeast cells, thereby creating a fluid regime. A mathematical expression relating the bubble agitation power to the fermentation parameters was obtained and used to design more efficient fermenter shapes. 相似文献
8.
Various reagents commonly used to enumerate viable helminth eggs from wastewater and sludge were evaluated for their potential to inactivate Ascaris eggs under typical laboratory conditions. Two methods were used to enumerate indigenous Ascaris eggs from sludge samples. All steps in the methods were the same except that in method I a phase extraction step with acid-alcohol (35% ethanol in 0.1 N H2SO4) and diethyl ether was used whereas in method II the extraction step was avoided by pouring the sample through a 38-μm-mesh stainless steel sieve that retained the eggs. The concentration of eggs and their viability were lower in the samples processed by method I than in the samples processed by method II by an average of 48 and 70%, respectively. A second set of experiments was performed using pure solutions of Ascaris suum eggs to elucidate the effect of the individual reagents and relevant combination of reagents on the eggs. The percentages of viable eggs in samples treated with acid-alcohol alone and in combination with diethyl ether or ethyl acetate were 52, 27, and 4%, respectively, whereas in the rest of the samples the viability was about 80%. Neither the acid nor the diethyl ether alone caused any decrease in egg viability. Thus, the observed inactivation was attributed primarily to the 35% ethanol content of the acid-alcohol solution. Inactivation of the eggs was prevented by limiting the direct exposure to the extraction reagents to 30 min and diluting the residual concentration of acid-alcohol in the sample by a factor of 100 before incubation. Also, the viability of the eggs was maintained if the acid-alcohol solution was replaced with an acetoacetic buffer. None of the reagents used for the flotation step of the sample cleaning procedure (ZnSO4, MgSO4, and NaCl) or during incubation (0.1 N H2SO4 and 0.5% formalin) inactivated the Ascaris eggs under the conditions studied. 相似文献
9.
Attached leaves of sunflower (Helianthus annuus L.) were exposed to 14CO2 during steady-state photosynthesis for 2 to 30 min in 345 l/l CO2 and 21% O2 at 29° C and a light intensity of 1300 E m-2s-1. Glycolic acid was extracted with water and diethyl ether, and was determined in the aqueous residue by high-pressure liquid column chromatography. The relative specific radioactivity of the glycolic acid synthesized during photosynthesis reached about 100% after 30 min of photosynthesis and was almost equal to that of the CO2 evolved during photorespiration, their ratio at all times being nearly one. These results provide strong in-vivo evidence that the glycolic acid is the substrate for CO2 evolved by sunflower leaves in light. 相似文献
10.
The effect of freezing and the influence of isolation medium on the recovery of pathogenic fungi from sputum 总被引:2,自引:0,他引:2
The primary objective of this study was to determine whether freezing sputa in dry ice had any effect on the recovery of pathogenic fungi. Sputa seeded with each of five fungi (Histoplasma capsulatum, Blastomyces dermatitidis, Cryptococcus neoformans, Coccidioides immitis, and Aspergillus fumigatus) were frozen and stored for 24, 48, and 72 hours on dry ice. H. capsulatum was killed, and only a few colonies of B. dermatitidis and C. neoformans were isolated from these sputa. However, A. fumigatus and C. immitis withstood the effects of freezing. A second objective was to compare the recovery of all five fungi from seeded sputa stored at room temperature for 24, 48, and 72 hours, on yeast extract-phosphate agar with NH4OH and on Sabhi agar. The yeast extract-phosphate agar with NH4OH was superior to Sabhi agar, for the isolation of all fungi studied, except A. fumigatus. 相似文献
11.
Mauro Centritto 《Plant biosystems》2013,147(1):31-37
ABSTRACT Birch (Betula pendula Roth.) seedlings were kept for two growing seasons under ambient (~350 µmol mol-1) and elevated (~700 µmol mol-1) [CO2]. The present study was designed to examine the effects of [CO2] and pot size on growth and carbon allocation under conditions of non-limiting water and nutrient supply, in order to separate the effects of source-sink interaction from the effects of nutrient deficiency. The manipulation of the source-sink relations had a strong influence on the growth response to elevated [CO2]. When the rooting volume was inadequate, it resulted in a source-sink imbalance which constrained growth under elevated [CO2]. When root exploration was unconstrained, total dry mass was significantly increased (by about 24%) under elevated [CO2]. However, the allometric relationships in allocation pattern and in morphogenetic development were not affected by either [CO2] or pot treatments when the saplings were of the same size. Thus, by constraining dry mass production, small sinks affected the magnitude of the growth responses to elevated [CO2], but did not affect the plant allocation pattern and allometric relationships when nutrient supply was non-limiting. However, by slowing down growth, sink restrictions counteract the speed-up of ontogeny which is the main effect of elevated [CO2] on tree growth. 相似文献
12.
The structure of 2-ketopropyl coenzyme M oxidoreductase/carboxylase (2-KPCC) has been determined in a state in which CO2 is observed providing insights into the mechanism of carboxylation. In the substrate encapsulated state of the enzyme, CO2 is bound at the base of a narrow hydrophobic substrate access channel. The base of the channel is demarcated by a transition from a hydrophobic to hydrophilic environment where CO2 is located in position for attack on the carbanion of the ketopropyl group of the substrate to ultimately produce acetoacetate. This binding mode effectively discriminates against H2O and prevents protonation of the ketopropyl leaving group.
Structured summary
2-KPCCbinds to 2-KPCC by x-ray crystallography (View interaction) 相似文献13.
Alexander A. DiIorio Ronald D. Cheetham Pamela J. Weathers 《Applied microbiology and biotechnology》1992,37(4):463-467
The effect of varying CO2 concentrations on the growth of beet and safflower hairy roots was measured for tissues cultured in nutrient mists and on solid media in chambers fed mixtures of humidified air supplemented with different CO2 concentrations. Hairy root tissue grown on solid media in air enriched with CO2 showed increased growth, as measured by dry weight increases vs air-fed controls. Growth increased with CO2 enrichment as much as 2.5 times more than the air-fed control for safflower at 1.0% CO2 and 1.4 times more than the air-fed control for beets at 1.5% CO2 over a 12-day period. Beet hairy root tissue was also cultured aeroponically in nutrient mists. Beet hairy root cultured aeroponically in nutrient mists enriched with 1.0% CO2 showed a 15% increase in biomass over a 7-day period vs tissue cultured in nutrient mists (with ambient air) or in shake flasks. The stimulation of root growth via CO2 enrichment reduced the time required for biomass accumulation.
Correspondence to: A. A. DiIorio 相似文献
14.
《Journal of bryology》2013,35(3):391-400
Abstract Sphagnum fuscum samples collected from an ombrotrophic bog were grown in a greenhouse at six water levels (0, 5, 10, 15, 25 and 30 cm) below the capitulum level and in four concentrations of CO2 (350, 700, 1000 and 2000 ppm). The cores of S. fuscum were treated for 87 days and length increment was measured by the plastic strip method and by innate time markers. Water content of the shoot, dry mass of the capitulum, dry mass per unit length of stem and production of dry mass were measured at the end of the experiment.The water content, capitulum dry mass, dry mass per unit length of stem, length increment and dry mass production differed markedly for S. fuscum grown in different water levels. With lower water levels, the water content of the shoot decreased and the dry mass of both the capitulum and unit length of stem increased. The total length increment was highest when the water level was at or near the capitulum level (0–10 cm). No clear trend in dry mass production on an areal basis could be found due to uncoupled responses in length increment and stem dry mass at the experimental water levels.Neither capitulum dry mass nor dry mass per unit length of stem showed distinct trends in S. fuscum grown at different ambient CO2 concentrations. Some increase in length increment and in dry mass production was detected at CO2 concentrations above 350 ppm, but this effect appeared only at high water levels. It is suggested that the low response in length increment and production to CO2 concentration resulted in part from insufficient moisture for photosynthesis at the lower water levels. Also, the possibility of increased nonstructural production is discussed. 相似文献
15.
Johan Van hemel Eddy L. Esmans Alex De Groot Roger A. Dommisse Jan M. Balzarini Erik D. De Clercq 《Nucleosides, nucleotides & nucleic acids》2013,32(6):1203-1221
Abstract 3-Bromo-5-(2-hydroxyethylthiomethyl)pyridine (7) was synthesized by reaction of 3-bromo-5-chloromethylpyridine hydrochloride (6) with the mono sodium salt of 2-mercaptoethanol. 3-Bromo-5-hydroxymethylpyridine (10) was, after protection as a silyl ether, converted to the 3-carboxy analogue using BuLi and CO2. After deprotection with NH4F, the alcohol function was chlorinated using SOCl2. Finally, attachment of the acyclic chain and ammonolysis gave the acyclic nicotinamide nucleosides. Treatment of the latter compounds with Lawesson's reagent gave the thioamide analogues. All compounds were identified by NMR and DCI-MS. The acyclic pyridine C-nucleosides were evaluated against a series of tumor-cell lines and a variety of viruses. No marked biological activity was found. 相似文献
16.
Plant growth and adaptation to cold and freezing temperatures in a CO2-enriched atmosphere have received little attention despite the predicted effects of elevated CO2 on plant distribution and productivity. Norway spruce [Picea abies (L.) Karst.] seedlings from latitudinally distinct seed sources (66°N and 60°N) were grown for one simulated growth season under controlled conditions in an atmosphere enriched in CO2 (70 Pa) and at ambient CO2 (40 Pa), combined factorially with low (3.6 mM) or high (15.7 mM) concentrations of nitrogen fertilization. There was a clear difference between the two provenances in height growth, in the timing of bud set, and in freezing tolerance. Nitrogen fertilization increased height growth in both provenances, while CO2
enrichment stimulated height growth only in the southern provenance. We found no significant effects of elevated CO2 or nitrogen fertilization on the timing of bud set. During cold acclimation, freezing tolerance increased from –10°C to –35°C, and there was a marked increase in all soluble sugars except inositol. Elevated CO2 in combination with high nitrogen led to a slight increased freezing tolerance in both provenances during the early stages of cold acclimation. However, towards the end of cold acclimation, elevated CO2
and high nitrogen led to reduced freezing tolerance in the southern provenance, while elevated CO2
and low nitrogen reduced freezing tolerance in the northern provenance. These results suggest that CO2 enrichment influences the development of freezing tolerance, and that these responses differ with available nitrogen and between provenances. 相似文献
17.
It was reported previously that Ogur and Rosen’s method for the determination of nucleic acids should be applied to fresh or durable yeast, after a freezing pretreatment with dry ice and ether. The fractionation of nucleic acids from the frozen yeast should precede with a complete elimination of alcohol-ether-soluble and acid-soluble compounds. It has been found that in Ogur and Rosen’s method, the elimination of the former compounds is complete, but the removal of acid-soluble compounds is unsatisfactory in the case of yeast.In order to improve this defect, the best conditions for the elution of acid-soluble compounds have been investigated in detail, and it has been found that water is the most suitable solvent. 相似文献
18.
Functional-Structural Analysis of Nitrogen-Cycle Bacteria in a Hypersaline Mat from the Omani Desert
Anaerobic microbial activity in northern peat soils most often results in more carbon dioxide (CO 2 ) production than methane (CH4) production. This study examined why methanogenic conditions (i.e., equal molar amounts of CH4 production and CO2 production) prevail so infrequently. We used peat soils from two ombrotrophic bogs and from two rheotrophic fens. The former two represented a relatively dry bog hummock and a wet bog hollow, and the latter two represented a forested fen and a sedge-dominated fen. We quantified gas production rates in soil samples incubated in vitro with and without added metabolic substrates (glucose, ethanol, H2/CO2). None of the peat soils exhibited methanogenic conditions when incubated in vitro for a short time (< 5 days) and without added substrates. Incubating some samples > 50 days without added substrates led to methanogenic conditions in only one of four experiments. The anaerobic CO2:CH4 production ratio ranged from 5:1 to 40:1 in peat soil without additions and was larger in samples from the dry bog hummock and forested fen than the wet bog hollow and sedge fen. Adding ethanol or glucose separately to peat soils led to methanogenic conditions within 5 days after the addition by stimulating rates of CH4 production, suggesting CH4 production from both hydrogenotrophic and acetoclastic methanogenesis. Our results suggest that methanogenic conditions in peat soils rely on a constant supply of easily decomposable metabolic substrates. Sample handling and incubation procedures might obscure methanogenic conditions in peat soil incubated in vitro. 相似文献
19.
Summary The stability of the monomeric enzymes -chymotrypsin and trypsin, and the oligomeric enzyme penicillin amidase in supercritical CO2 has been studied. They were found to be partly denatured during the depressurization step. The degree of denaturation was larger in humid CO2 than in dry CO2. Enzymes with S-S bridges (-chymotrypsin; trypsin) were denatured to a lesser degree than the enzyme without cysteine (penicillin amidase). These results and electrophoretic and spectroscopic analysis indicated that the denaturation was caused by partial unfolding during the depressurization step. 相似文献
20.
Aner Gurvitz Hanspeter Rottensteiner Barbara Hamilton Helmut Ruis Andreas Hartig I. W. Dawes Maximilian Binder 《Histochemistry and cell biology》1998,110(1):15-26
Sporulation in the yeast Saccharomyces cerevisiae is a meiotic developmental process that occurs in MAT
a/MATα heterozygotes in response to nutrient deprivation. Here, the fate and role of peroxisomes during sporulation and germination
has been examined by a combination of immunoelectron microscopy and the use of pex mutants defective in peroxisomal functions. Using a green fluorescent protein probe targeted to peroxisomes we show that
peroxisomes are inherited through meiosis and that they do not increase in number either during sporulation or spore germination.
In addition, there is no requirement for peroxisome degradation prior to spore packaging. Unlike the situation in filamentous
fungi, peroxisomes do not proliferate during the yeast life cycle. Functional peroxisomes are dispensable for efficient meiotic
development on acetate medium since homozygous Δpex6 diploids sporulated well and produced mature spores that were resistant to diethyl ether. Like haploids, diploid cells can
proliferate their peroxisomes in response to oleate as sole carbon source in liquid medium, but under these conditions they
do not sporulate. On solid oleate medium, homozygous pex5,Δpex6, and pex7 cells were unable to sporulate efficiently, whereas the wild type was. The results presented here are discussed in terms
of the transmission of organelles to progeny cells.
Accepted: 19 December 1997 相似文献