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91.
A. Henry Latorella Susan K. Bromberg Kent Lieber James Robinson 《Journal of phycology》1981,17(2):211-214
Fifteen nitrate assimilation-deficient mutants of the euryhaline green alga, Dunaliella tertiolecta Butcher were selected by their chlorate resistance. Ten mutants, unable to grow on NO3? but able to grow on NO2?, had no detectable nitrate reductase activity. Five mutants, unable to grow on either NO3? or NO2?, had depressed levels of both nitrate and nitrite reductase. A method for assaying methyl viologen-nitrate reductase in the presence of nitrite reductase is described. 相似文献
92.
Summary The production of nitrate in an old established dune grassland soil and its uptake by plants was studied by comparing amounts of mineral nitrogen and numbers of nitrifying bacteria in the rhizosphere on the one hand, and on the other accumulated nitrate and levels of nitrate reductase (NaR) of individual plants of three Plantago species,i. e., P. major, P. lanceolata andP. coronopus. For these three Plantago species andP. media basal levels of NaR in the absence of nitrate were determined in plants grown in culture solutions. The basal NaR levels ofP. major andP. media (species occurring on nutrient-rich soils) were significantly higher than those ofP. lanceolata andP. coronopus (species found on nutrient-poor soils). NaR activity increased in the presence of nitrate and was suppressed by ammonium.From the numbers of nitrifying bacteria in the rhizosphere and NaR activity in the leaves it was concluded that nitrate was produced in the root environments of the three Plantago species and that the compound was taken up by the plants. NaR activities and numbers of nitrifying bacteria were higher for individuals ofP. major than for those ofP. lanceolata andP. coronopus. No correlation was found between the ammonium levels and the numbers of nitrifying bacteria in the soil, and no indications of inhibition of nitrifying bacteria in the rhizosphere were obtained. For individuals ofP. lanceolata a correlation was found between the numbers of nitrifying bacteria in the soil and NaR activity in the leaves. The results are discussed in relation to the ecological habitats of the three species.Grassland Species Research Group Publication No.38. 相似文献
93.
Work is described which suggests that glutamine synthetase (GS) could play an important and direct regulatory role in the control of NO3 assimilation by the alga. In both steady-state cells and ones disturbed physiologically by changes in light or nitrogen supply the assimilation of NO3 appears to be limited by the activity of GS. Moreover although in normal cells NH3 can completely inhibit NO3 uptake, promote the deactivation of nitrate reductase (NR) and repress the synthesis of NR and nitrite reductase (NIR), these controls are relaxed in cells in which GS is deactivated by treatment with L-methionine-DL-sulfoximine (MSO). It is proposed that the reversible deactivation of GS may play an important part in the regulation of NO3 assimilation although it is still not clear whether the enzyme itself or products of its metabolism are responsible.Abbreviations GS
glutamine synthetase
- GSs
glutamine synthetase, synthetase activity
- GSt
glutamine synthetase, transferase activity
- NR
nitrate reductase
- NIR
nitrite reductase
- GDH
glutamate dehydrogenase
- CHX
cycloheximide
- MSO
L-methionine-DL-sulfoximine
- FAD
flavine adenine dinucleotide 相似文献
94.
Phytochrome mediated induction of nitrate reductase activity in etiolated maize leaves 总被引:1,自引:0,他引:1
L. VIJAYA MOHAN RAO NEERAJ DATTA SUDHIR K. SOPORY SIPRA GUHA-MUKHERJEE 《Physiologia plantarum》1980,50(2):208-212
The effects of red and far-red light on the enhancement of in vitro nitrate reductase activity and on nitrate accumulation in etiolated excised maize leaves were examined. Illumination for 5 min with red light followed by a 4-h dark period caused a marked increase in nitrate reductase activity, whereas a 5-min illumination with far-red light had no effect on the enzyme activity. The effect of red light was completely reversed by a subsequent illumination with the same period of far-red light. Continuous far-red light also enhanced nitrate reductase activity. Both photoreversibility by red and far-red light and the operation of high intensity reaction under continuous far-red light indicated that the induction of nitrate reductase was mediated by phytochrome. Though nitrate accumulation was slightly enhanced by red and continuous far-red light treatments by 17% and 26% respectively, this is unlikely to account for the entire increase of nitrate reductase activity. The far-red light treatments given in water, to leaves preincubated in nitrate, enhanced nitrate reductase activity considerably over the dark control. The presence of a lag phase and inhibition of increase in enzyme activity under continuous far-red light-by tungstate and inhibitors of RNA synthesis and protein synthesis-rules out the possibility of activation of nitrate reductase and suggests de novo synthesis of the enzyme affected by phytochrome. 相似文献
95.
H.S. Srivastava 《Phytochemistry》1980,19(5):725-733
Nitrate reductase is one of the most important enzymes in the assimilation of exogenous nitrate—the predominant form of nitrogen available to green plants growing in soil. Activity of this enzyme in plants gives a good estimate of the nitrogen status of the plant and is very often correlated with growth and yield. Although it is difficult to explain the physiological significance and the mechanism of effects of several factors on the enzyme activity, in some cases suitable postulates have been advanced. In general, the enzyme activity in a plant tissue is a balance between its relative rates of synthesis/degradation and activation/inactivation. Factors may affect the overall activity by interfering with either of these processes. 相似文献
96.
Abstract Effect of ammonium on in vivo activity of nitrate reductase in roots, shoots and leaves of maize (Zea mays L.) seedlings was studied in relation to light/dark conditions and EDTA supply. Supply of 5 mM (NH4)2SO4 increased the steady state level of enzyme only in leaves and in light, while it had no effect in roots and shoots and in the dark. The substrate induction of enzyme was also little affected by 1 to 10 mM (NH4)2SO4 in roots and shoots. In the leaves the activity in the dark was either inhibited (minus EDTA) or stimulated (plus EDTA) by 5 to 10 mM (NH4)2SO4. The activity was stimulated in the light also in the presence of EDTA at higher concentrations of ammonium. When different concentrations of ammonium were supplied without any exogenous nitrate in the light, the enzyme activity increased at low concentration and was either inhibited or unaffected at higher concentrations depending upon the tissue used. Supply of EDTA with ammonium modified its effect to some extent. It is suggested that the effect of ammonium on nitrate reductase activity depends upon the tissue used and the effective concentration of the ammonium. 相似文献
97.
Gale W. Rafter 《Biological trace element research》1982,4(2-3):191-197
Leukocytes incubated with Cu(II) showed a decrease in both glutathione reductase activity and reduced glutathione content.
The glucose 6-phosphate dehydrogenase activity under the same conditions was not affected. Serum albumin added to mixtures
prevented the loss of enzyme activity, whiled-penicillamine andl-histidine had little effect. Prior oxidation of the cell-reduced glutathione did not diminish the enzyme inhibitory action
of Cu(II). The amount of regeneration of reduced glutathione in leukocytes previously treated with diamide to oxidize their
reduced glutathione was a function of Cu(II) concentration in the media. No evidence was obtained that elevated serum ceruloplasmin
levels in rabbits, nor incubation of leukocytes in vitro with ceruloplasmin, affect leukocyte glutathione reductase activity.
It was proposed that the major mechanism by which copper affects glutathione metabolism in leukocytes is by inhibition of
glutathione reductase. 相似文献
98.
99.
100.
Pyrroline-5-carboxylic acid reductase from soybean leaves 总被引:1,自引:0,他引:1
Pyrroline-5-carboxylic acid reductase was purified 40-fold from soybean leaves (Glycine max L. var Corsoy). The enzyme was fairly unstable, had a broad pH optimum, and was inactivated by heat and acid; NADH and NADPH both served as cofactors. It had a higher activity with NADH (about 4 ×) compared to NADPH, but a lower Km for NADPH. NADP+ inhibited both the NADH- and NADPH-dependent activity. Sulfhydryl group blocking agents reduced the activity as did the carbonyl blocking agent, NH2OH. Thiazolidine-4-carboxylic acid and phosphate inhibited the enzyme and proline inhibited only at high concentrations. ATP, GTP, and CTP were all effective inhibitors of both the NADH- and NADPH-dependent activity. Phosphorylated nucleotide inhibition was reversed by Mg2+ ions. 相似文献