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101.
《Bioscience, biotechnology, and biochemistry》2013,77(11):2020-2023
Mixed rumen ciliate protozoa (mainly Entodiniinae) from goats have two kinds of protease; one has a pH optimum of 3.0, the other is active at neutral or alkaline pH. The protease active at neutral or alkaline pH was partially purified from the supernatant after centrifugation of sonicated mixed rumen ciliate protozoa. The supernatant was chromatographed on Bio-Gel A-1.5m and a partially purified protease was obtained. This protease had a molecular weight of more than 400,000. When the sonicated protozoa were heated at 55°C for 15min, the active peak from the Bio-Gel A-1.5m column was shifted to a lower molecular weight, 27,000. The high molecular weight protease was strongly activated by high temprature and SDS, and inhibited by E-64 c. The protease degraded many proteins including those found in rumen bacteria. These findings suggest that rumen ciliate protozoa have high molecular weight protease that plays a role in the digestion of feed and bacterial protein. 相似文献
102.
Nitrite is reduced to nitric oxide (NO) in the oral cavity. The NO generated can react with molecular oxygen producing reactive nitrogen species. In this study, reduction of nitrite to NO was observed in bacterial fractions of saliva and whole saliva. Formation of reactive nitrogen species from NO was detected by measuring the transformation of 4,5-diaminofluorescein (DAF-2) to triazolfluorescein (DAF-2T). The transformation was fast in bacterial fractions but slow in whole saliva. Salivary components such as ascorbate, glutathione, uric acid and thiocyanate inhibited the transformation of DAF-2 to DAF-2T in bacterial fractions without affecting nitrite-dependent NO production. The inhibition was deduced to be due to scavenging of reactive nitrogen species, which were formed from NO, by the above reagents. The transformation of DAF-2 to DAF-2T was faster in bacterial fractions and whole saliva which were prepared 1–4?h after tooth brushing than those prepared immediately after toothbrushing. Increase in the rate as a function of time after toothbrushing seemed to be due to the increase in population of bacteria which could reduce nitrite to NO. The results obtained in this study suggest that reactive nitrogen species derived from NO are continuously formed in the oral cavity and that the reactive nitrogen species are effectively scavenged by salivary redox components in saliva but the scavenging is not complete. 相似文献
103.
《Bioscience, biotechnology, and biochemistry》2013,77(11):1953-1954
Eight gibberellins (GAs) were identified in extracts of buds of Aralia cordata by full scan GC/MS and by Kovats retention indices. These GAs comprised five GAs on the early-13-hydroxylation pathway [GA1, GA19, GA20, GA44, and GA53] and three other GAs [GA4, GA15, and GA37]. The major GAs were GA19 and GA44. 相似文献
104.
Nitrogen (N) is an essential nutrient in the sea and its distribution is controlled by microorganisms. Within the N cycle, nitrite (NO2−) has a central role because its intermediate redox state allows both oxidation and reduction, and so it may be used by several coupled and/or competing microbial processes. In the upper water column and oxygen minimum zone (OMZ) of the eastern tropical North Pacific Ocean (ETNP), we investigated aerobic NO2− oxidation, and its relationship to ammonia (NH3) oxidation, using rate measurements, quantification of NO2−-oxidizing bacteria via quantitative PCR (QPCR), and pyrosequencing. 15NO2− oxidation rates typically exhibited two subsurface maxima at six stations sampled: one located below the euphotic zone and beneath NH3 oxidation rate maxima, and another within the OMZ. 15NO2− oxidation rates were highest where dissolved oxygen concentrations were <5 μM, where NO2− accumulated, and when nitrate (NO3−) reductase genes were expressed; they are likely sustained by NO3− reduction at these depths. QPCR and pyrosequencing data were strongly correlated (r2=0.79), and indicated that Nitrospina bacteria numbered up to 9.25% of bacterial communities. Different Nitrospina groups were distributed across different depth ranges, suggesting significant ecological diversity within Nitrospina as a whole. Across the data set, 15NO2− oxidation rates were decoupled from 15NH4+ oxidation rates, but correlated with Nitrospina (r2=0.246, P<0.05) and NO2− concentrations (r2=0.276, P<0.05). Our findings suggest that Nitrospina have a quantitatively important role in NO2− oxidation and N cycling in the ETNP, and provide new insight into their ecology and interactions with other N-cycling processes in this biogeochemically important region of the ocean. 相似文献
105.
The yields of nitric oxide from 1 mM and 10 mM sodium dithionite in 5 or 150 mM solutions of HEPES buffer (pH 7.4) differed by a factor of 200. Dithionite acted as both a strong reducing agent and an agent responsible for local acidification of the solutions without significant changes in pH. The concentration of nitric oxide was estimated by electron paramagnetic resonance (EPR) by monitoring its incorporation into water-soluble complexes of Fe with N-methyl-D-glucamine dithiocarbamate (MGD), which resulted in the formation of EPR-detectable mononitrosyl complexes of iron. Ten seconds after dithionite addition, the concentration of mononitrosyl iron complexes reached 2 μM, whereas it did not become greater than 0.01 μM in 5 mM HEPES buffer. It has been suggested that this difference results from a longer lifetime of a localized decrease in pH in a weaker buffer solution. This time could be long enough for the protonation of some nitrite molecules. Nitrous acid thus formed decomposed to nitric oxide. A difference in nitric oxide formation from nitrite in weak and strong buffer solutions was also observed in the presence of hemoglobin (0.3 mM) or serum albumin (0.5 mM). However, in the weak buffer the nitric oxide yield was only three-four times greater than in the strong buffer. An increase in the nitric oxide yield from nitrite was observed in solutions containing both proteins. A significant amount of nitric oxide from nitrite was formed in mouse liver preparation subjected to freezing and thawing procedure followed by slurrying in 150 mM HEPES buffer (pH 7.4) and dithionite addition (10 mM). We suggest that the presence of zones with lowered pH values in cells and tissues may be responsible for the predominance of the acidic mechanism of nitric oxide formation from nitrite. The contribution of nitric oxide formation from nitrite catalyzed by heme-containing proteins as nitrite reductases may be minor under these conditions. 相似文献
106.
L. Dendooven C. Vega-Jarquin C. Cruz-Mondragon O. Van Cleemput R. Marsch 《Plant and Soil》2006,279(1-2):243-252
Induction of assimilatory NO
3
−
reduction through the application of an easily decomposable substrate in alkaline–saline soils of the former lake Texcoco
(Mexico) resulted in a fast immobilization of NO
3
−
in excess of N required for metabolic activity and the release of large concentrations of NO
2
−
and smaller amounts of NH
4
+
. We postulated that this was regulated by the amounts of NO
3
−
and glucose added, and affected by the specific characteristics of soil from the former lake Texcoco. This was investigated
by spiking soils of different electrolytic conductivity (EC) 56.0 dS m−1 (soil A of Texcoco) and 11.6 dS m−1 (soil B of Texcoco) with different concentrations of NO
3
−
and glucose while dynamics of CO2, NH
4
+
, NO
2
−
and NO
3
−
were monitored in an aerobic incubation for 7 days. For comparison reasons (control) an agricultural soil with low EC (0.3 dS
m−1) was included as well. In the agricultural soil, 67% of the added glucose mineralized within 7 days, but only 15% in soil
A of Texcoco and 20% in soil B of Texcoco. The application of NO
3
−
to the agricultural soil added with glucose increased cumulative production of CO2 1.2 times, 1.5 times in soil A of Texcoco and 1.8 times in soil B of Texcoco. Concentration of NO
2
−
increased to > 100 mg NO
2
−
-N kg−1 when 1000 mg glucose-C kg−1 and 500 mg NO
3
−
-N kg−1 were added to soil A and B of Texcoco, but remained < 3 mg NO
2
−
-N kg−1 in the agricultural soil. The ratio between the cumulative production of CO2 and the decrease in concentration of NO
3
−
was approximately one in soil A and B of Texcoco, but 10 in the agricultural soil after 3 days. It was found that micro-organisms
in the alkaline–saline soil of the former lake Texcoco were capable of immobilizing large quantities of NO
3
−
when an easy decomposable substrate was available in excess of what might be required for metabolic activity while producing
large concentrations of NO
2
−
, but these phenomena were absent in an agricultural soil. In soil of Texcoco, concentrations of NO
2
−
and NH
4
+
increased with increased salinity and availability of NO
3
−
. This ability to remove large quantities of NO
3
−
under these conditions and then utilize it at a later time might benefit micro-organisms of the N limited alkaline–saline
soils of Texcoco. 相似文献
107.
108.
Higher plant responses to environmental nitrate 总被引:12,自引:0,他引:12
109.
Tritordeum is a fertile amphiploid derived from durum wheat (Triticum turgidum L. conv. durum) × a wild barley (Hordeum chilense Roem. et Schultz.). The organic nitrogen content of tritordeum grain (34 mg g-1 DW) was significantly higher than that of its wheat parent (25 mg g-1 DW). Leaf and root nitrogen content became higher in tritordeum than in wheat after four weeks of growth, independently of
the nitrogen source (either NO3
- or NH4
+). Under NO3
- nutrition, tritordeum generally exhibited higher levels of nitrate reductase (NR) activity than wheat. Nitrite reductase
(NiR) levels were however lower in tritordeum than in its wheat parent. In NH4
+-grown plants, both NR and NiR activities progressively decreased in the two species, becoming imperceptible after 3 to 5
weeks of growth. Results indicate that, in addition to a higher rate of NO3
- reduction, other physiological factors must be responsible for the greater accumulation of organic nitrogen in tritordeum
grain. 相似文献
110.
Ammonium can stimulate nitrate and nitrite reductase in the absence of nitrate in Clematis vitalba 总被引:3,自引:1,他引:3
R. A. Bungard A. Wingler J. D. Morton M. Andrews M. C. Press & J. D. Scholes 《Plant, cell & environment》1999,22(7):859-866
Nitrogen assimilation was studied in the deciduous, perennial climber Clematis vitalba. When solely supplied with NO3– in a hydroponic system, growth and N-assimilation characteristics were similar to those reported for a range of other species. When solely supplied with NH4+, however, nitrate reductase (NR) activity dramatically increased in shoot tissue, and particularly leaf tissue, to up to three times the maximum level achieved in NO3– supplied plants. NO3– was not detected in plant material that had been solely supplied with NH4+, there was no NO3– contamination of the hydroponic system, and the NH4+-induced activity did not occur in tobacco or barley grown under similar conditions. Western Blot analysis revealed that the induction of NR activity, either by NO3– or NH4+, was matched by NR and nitrite reductase protein synthesis, but this was not the case for the ammonium assimilation enzyme glutamine synthetase. Exposure of leaf disks to N revealed that NO3– assimilation was induced in leaves directly by NO3– and NH4+ but not glutamine. Our results suggest that the NH4+-induced potential for NO3– assimilation occurs when externally sourced NH4+ is assimilated in the absence of any NO3– assimilation. These data show that the potential for nitrate assimilation in C. vitalba is induced by a nitrogenous compound in the absence of its substrate and suggest that NO3– assimilation in C. vitalba may have a significant role beyond the supply of reduced N for growth. 相似文献