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271.
Distribution of polyamines and their related catabolic enzyme in etiolated and light-grown leguminosae seedlings 总被引:3,自引:0,他引:3
Diamine-oxidase (DAO; EC 1.4.3.6) activity and di-and polyamine levels were estimated along the epicotyl and root of light-grown and etiolated lentil (Lens culinaris Medicus) and pea (Pisum sativum L.) seedlings. The activity of DAO was higher in etiolated epicotyls than in lightgrown ones. In both species there was a positive correlation between DAO activity and the diamine (putrescine and cadaverine) levels along the whole epicotyl and root. Polyamine (spermine and spermidine) distribution seemed to be associated with the meristematic and elongating zone of the epicotyl and root. The physiological function of DAO is discussed in relation to its possible role in providing hydrogen peroxide to peroxidase-dependent reactions occurring in the cell wall.Abbreviations CAD
cadaverine
- DA
diamine
- DAO
diamine oxidase
- PA
polyamine
- PUT
putrescine
- SPD
spermidine
- SPM
spermine 相似文献
272.
Chloroplasts with high rates of photosynthetic O2 evolution (up to 120 mol O2· (mg Chl)-1·h-1 compared with 130 mol O2· (mg Chl)-1·h-1 of whole cells) were isolated from Chlamydomonas reinhardtii cells grown in high and low CO2 concentrations using autolysine-digitonin treatment. At 25° C and pH=7.8, no O2 uptake could be observed in the dark by high- and low-CO2 adapted chloroplasts. Light saturation of photosynthetic net oxygen evolution was reached at 800 mol photons·m-2·s-1 for high- and low-CO2 adapted chloroplasts, a value which was almost identical to that observed for whole cells. Dissolved inorganic carbon (DIC) saturation of photosynthesis was reached between 200–300 M for low-CO2 adapted chloroplasts, whereas high-CO2 adapted chloroplasts were not saturated even at 700 M DIC. The concentrations of DIC required to reach half-saturated rates of net O2 evolution (Km(DIC)) was 31.1 and 156 M DIC for low- and high-CO2 adapted chloroplasts, respectively. These results demonstrate that the CO2 concentration provided during growth influenced the photosynthetic characteristics at the whole cell as well as at the chloroplast level.Abbreviations Chl
chlorophyll
- DIC
dissolved inorganic carbon
- Km(DIC)
coneentration of dissolved inorganic carbon required for the rate of half maximal net O2 evolution
- PFR
photon fluence rate
- SPGM
silicasol-PVP-gradient medium 相似文献
273.
The short-term, in-vivo response to elevated CO2 of ribulose-1,5-bisphosphate carboxylase (RuBPCase, EC 4.1.1.39) activity, and the pool sizes of ribulose 1,5-bisphosphate, 3-phosphoglyceric acid, triose phosphates, fructose 1,6-bisphosphate, glucose 6-phosphate and fructose 6-phosphate in bean were studied. Increasing CO2 from an ambient partial pressure of 360–1600 bar induced a substantial deactivation of RuBPCase at both saturating and subsaturating photon flux densities. Activation of RuBPCase declined for 30 min following the CO2 increase. However, the rate of photosynthesis re-equilibrated within 6 min of the switch to high CO2, indicating that RuBPCase activity did not limit photosynthesis at high CO2. Following a return to low CO2, RuBPCase activation increased to control levels within 10 min. The photosynthetic rate fell immediately after the return to low CO2, and then increased in parallel with the increase in RuBPCase activation to the initial rate observed prior to the CO2 increase. This indicated that RuBPCase activity limited photosynthesis while RuBPCase activation increased. Metabolite pools were temporarily affected during the first 10 min after either a CO2 increase or decrease. However, they returned to their original level as the change in the activation state of RuBPCase neared completion. This result indicates that one role for changes in the activation state of RuBPCase is to regulate the pool sizes of photosynthetic intermediates.Abbreviations and symbols
A
net CO2 assimilation rate
- Ca
ambient CO2 partial pressure
- Ci
intercellular CO2 partial pressure
- CABP
2-carboxyarabinitol 1,5-bisphosphate
- kcat
catalytic turnover rate per RuBPCase molecule
- PFD
photon flux density (400 to 700 nm on an area basis)
- PGA
3-phosphoglyceric acid
- Pi
orthophosphate
- RuBP
ribulose 1,5-bisphosphate
- RuBPCase
ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) 相似文献
274.
The red light-stimulated component of unrolling in sections from 7-d-old dark-grown barley (Hordeum vulgare L.) leaves is inhibited by ethyleneglycol-bis-(-aminoethyl ether)-N,N,N,N-tetracetic acid (EGTA). A free-Ca2+ activity of less than 40 M restores the ability to respond to red light, but only if supplied within 1 h of red light. Magnesium ions are an ineffective substitute. At least two processes in unrolling appear to be Ca2+-sensitive.Fluence-response measurements indicate that the levels of the far-red-absorbing from of phytochrome (Pfr) still present 4 h after red-light treatment should be above saturation for the unrolling response; consequently, loss of Pfr does not explain the loss in effectiveness of Ca2+ during prolonged EGTA treatment. However, if a further red-light treatment is given simultaneously with Ca2+ addition 4 h after the initial light stimulus, then full unrolling occurs in EGTA-treated sections. These data indicate that, under normal circumstances, a functional change in the properties of Pfr must occur, uncoupling it from the transduction chain.Abbreviations EGTA
ethyleneglycol-bis-(-aminoethylether)-N,N,N,N,-tetracetic acid
- FR
far-red light
- Mes
2-(N-morpholino)ethanesulphonic, acid
- Pfr
far-red absorbing form of phytochrome
- Pr
red-absorbing form of phytochrome
- R
red light 相似文献
275.
Hubert Felle 《Planta》1988,176(2):248-255
In cells of Zea mays (root hairs, coleoptiles) and Riccia fluitans (rhizoids, thalli) intracellular Ca2+ and pH have been measured with double-barrelled microelectrodes. Free Ca2+ activities of 109–187 nM (Riccia rhizoids), 94–160 nM (Riccia thalli), 145–231 nM (Zea root hairs), 84–143 nM (Zea coleoptiles) were found, and therefore identified as cytoplasmic. In a few cases (Riccia rhizoids), free Ca2+ was in the lower millimolar range (2.3±0.8 mM). A change in external Ca2+ from 0.1 to 10 mM caused an initial and short transient increase in cytoplasmic free Ca2+ which finally levelled off at about 0.2 pCa unit below the control, whereas in the presence of cyanide the Ca2+ activity returned to the control level. It is suggested that this behaviour is indicative of active cellular Ca2+ regulation, and since it is energy-dependent, may involve a Ca2+-ATPase. Acidification of the cytoplasmic pH and alkalinization of the vacuolar pH lead to a simultaneous increase in cytoplasmic free Ca2+, while alkalinization of pHc decreased the Ca2+ activity. Since this is true for such remote organisms as Riccia and Zea, it may be concluded that regulation of cytoplasmic pH and free Ca2+ are interrelated. It is further concluded that double-barrelled microelectrodes are useful tools for investigations of intracellular ion activities in plant cells.Symbols and abbreviations m, m
membrane potential difference, changes thereof
- PVC
polyvinylchloride 相似文献
276.
277.
G Floyd-Smith 《Journal of cellular biochemistry》1988,38(1):13-21
The levels of a (2'-5')An-dependent endonuclease (RNase L) were determined in extracts prepared from murine L cells and Ehrlich ascites tumor (EAT) cells by measuring specific binding of protein to a labeled derivative of (2'-5')An, (2'-5')A3[32P]pCp. RNase L levels were found to depend both on interferon (IFN) treatment and on cell growth conditions. Treatment of murine L cells and EAT cells with 100-2,000 IRU IFN beta or IFN gamma resulted in a similar 2-4-fold increase in the levels of RNase L when cells were present at low density. The levels of RNase L were also shown to increase 2-3-fold as cells approached saturation density. Serum-starved cells also displayed relatively high levels of RNase L. RNase L levels in cells maintained at high cell density did not change appreciably following treatment with IFN beta or IFN gamma. Regulation of RNase L levels by cell growth conditions as well as by IFN beta or IFN gamma treatment suggests that RNase L may play an important role in regulating the levels of cellular mRNAs as well as acting to degrade viral RNAs. 相似文献
278.
The metabolism and mutagenic activation of 2-acetylaminofluorene by human and rat hepatocytes and kidney cells were measured. High performance liquid chromatography was used to separate the 2-acetylaminofluorene metabolites, and a cell-mediated Salmonella typhimurium mutagenesis assay was used to detect mutagenic intermediates. Rat and human differences were observed with cells from both organs and levels of metabolism and mutagenesis were higher in human cells. Within a species, liver and kidney cell differences were also evident, with levels of hepatocyte-mediated metabolism and mutagenesis being greater than kidney cells. Human inter-individual variation was apparent with cells from both organs, but the variation observed was significantly greater in hepatocytes than kidney cells. A knowledge of such differences, including an understanding that they may vary with the chemical being studied, should be useful in the extrapolation of rodent carcinogenesis data to humans.Abbreviations AAF
2-acetylaminofluorene
- AF
2-aminofluorene
- DMSO
dimethylsulfoxide
- HPLC
high performance liquid chromatography
- N-OH-AAF
N-hydroxy-2-acetylaminofluorene
- 1-OH-AAF
1-hydroxy-2-acetylaminofluorene
- 3-OH-AAF
3-hydroxy-2-acetylaminofluorene
- 5/9-OH-AAF
a combination of 5 and 9-hydroxy-2-acetylaminofluorene
- 7-OH-AAF
7-hydroxy-2-acetylaminofluorene
- 8-OH-AAF
8-hydroxy-2-acetylaminofluorene 相似文献
279.
Richard C. Woodman John T. Curnutte Bernard M. Babior 《Free radical biology & medicine》1988,5(5-6):355-361
We examined the effects of the recombinant human colony stimulating factors GM-CSF and G-CSF, cycloheximide (a protein synthesis inhibitor) and dihydrocytochalasin B (a microfilament disrupting agent) upon FMLP (N-formyl-methionyl-leucylphenylalanine)-stimulated O2 − production by neutrophils. We confirmed a time dependent augmentation of O2 − production following preincubation of neutrophils either alone or with colony stimulating factors. Furthermore, we found that GM-CSF, but not G-CSF, increased O2 − production at some concentrations of the stimulus. Preincubation of neutrophils with cycloheximide in the absence of CSF caused a marked fall in O2−-production that was first evident at 2 hours. The fall in O2−-forming capacity caused by cycloheximide was much less pronounced if dihydrocytochalasin B was also included in the preincubation buffer. These findings suggest a previously unrecognized role for de novo protein synthesis in maintaining the ability of neutrophils to manufacture O2−, and support earlier studies indicating that the cycling of FMLP receptors between the cell membrane and an intracellular compartment is important in determining the magnitude of the respiratory burst in FMLP-stimulated neutrophils. 相似文献
280.
符云峰 《中国生物化学与分子生物学报》1988,4(1):84-87
本研究确定了在0℃条件下,(Na~++K~+)-ATP酶纯化制备物与5mmol/L Na~+或Mg~(2+)在5mmol/L咪唑(pH7.4)环境中预保温30分钟,然后进行磷酸化,可以获得最高磷酸化水平,Na~+或Mg~(2+)的K_(0.5)值分别为0.29mmol/L或0.35mmol/L;以ADP代替Na~+和Mg~(2+)与酶预保温,对E_2向E_1转变无任何影响,而与Na~+、Mg~(2+)一起存在时则能加强Na~+及Mg~2的预保温效果。 相似文献