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Query: EC:1.7.1.1 (nitrate reductase)
 3,728 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Indoor cultivation experiment and plot field experiment were conducted to study the effect of lignosulfonates on urea nitrogen transformation in soil and the mechanism of controlling nitrate pollution in vegetable. Results showed that lignosulfonates behaved inhibition effect on urea hydrolysis compared with the contrast treatment, the contents of remainder urea nitrogen treated with lignosulfonates was more than that of another kind of urease inhibitor hydroquinone in soil after 69 hours' cultivation. Lignosulfonates could reduce contents of nitrate in cabbage, it as well increase contents of vitamin C in a large degree, enhance the nitrate reductase activity, then accelerated nitrogen assimilation in plants. The urease activity was lower and contents of ammonium nitrogen in soil was larger after ingathering, lignosulfonates could keep nitrogen release slowly, and could be used as a kind of effective inhibitor to nitrogen fertilizer in the controlled-release fertilizers.
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PMID:[Effect of lignosulfonates on controlling of urea nitrogen transformation and nitrate accumulation in vegetable]. 1471 77

Penicillium griseoroseum has been studied because of its efficient pectinases production. In this work, the Penicillium griseoroseum nitrate reductase gene was characterized, transcriptionally analyzed in different nitrogen sources, and used to create a phylogenetic tree and to develop a homologous transformation system. The regulatory region contained consensus signals involved in nitrogen metabolism and the structural region was possibly interrupted by 6 introns coding for a deduced protein with 864 amino acids. RT-PCR analysis revealed high amounts of niaD transcript in the presence of nitrate. Transcription was repressed by ammonium, urea, and glutamine showing an efficient turnover of the niaD mRNA. Phylogenetics analysis showed distinct groups clearly separated in accordance with the classical taxonomy. A mutant with a 122-bp deletion was used in homologous transformation experiments and showed a transformation frequency of 14 transformants/microg DNA. All analyzed transformants showed that both single- and double-crossover recombination occurred at the niaD locus. The establishment of this homologous transformation system is an essential step for the improvement of pectinase production in Penicillium griseoroseum.
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PMID:Characterization, regulation, and phylogenetic analyses of the Penicillium griseoroseum nitrate reductase gene and its use as selection marker for homologous transformation. 1564 6

Certain amino acids inhibit growth of tobacco (Nicotiana tabacum L. var. xanthi), tomato (Lycopersicon esculentum) carrot (Daucus carota), and soybean (Glycerine max L. co. Mandarin) cell cultures when nitrate or urea are the nitrogen sources but not when ammonia is the nitrogen source. These amino acids also inhibit development of nitrate reductase activity (NADH:nitrate oxidoreductase EC 1.6.6.1) in tobacco and tomato cultures. Threonine, the most inhibitory amino acid, also inhibits nitrate uptake in tobacco cells. Arginine, and some other amino acids, abolish the inhibition effects caused by other amino acids. We suggest that amino acids inhibit assimilation of intracellular ammonium into amino acids in cells grown on nitrate or urea.
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PMID:Nitrogen metabolism in plant cell suspension cultures: I. Effect of amino acids on growth. 1665 49

The effects of N source (6 mm nitrogen as NO(3) (-) or urea) and tungstate (0, 100, 200, 300, and 400 mum Na(2) WO(4)) on nitrate metabolism, nodulation, and growth of soybean (Glycine max [L.] Merr.) plants were evaluated. Nitrate reductase activity and, to a lesser extent, NO(3) (-) content of leaf tissue decreased with the addition of tungstate to the nutrient growth medium. Concomitantly, nodule mass and acetylene reduction activity of NO(3) (-)-grown plants increased with addition of tungstate to the nutrient solution. In contrast, nodule mass and acetylene reduction activity of urea-grown plants decreased with increased nutrient tungstate levels. The acetylene reduction activity of nodulated roots of NO(3) (-)-grown plants was less than 10% of the activity of nodulated roots of urea-grown plants when no tungstate was added. At 300 and 400 mum tungstate levels, acetylene reduction activity of nodulated roots of NO(3) (-)-grown plants exceeded the activity of comparable urea-grown plants.Addition of tungstate to the nutrient solution decreased plant growth, regardless of the N source, although the effect was more pronounced with NO(3) (-) nutrition. The increased nodulation and decreased nitrate reductase activity noted with plants grown in the presence of tungstate and a high (6 mm) external supply of NO(3) (-) suggests that NO(3) (-) does not directly inhibit nodulation but rather affects nodulation indirectly through subsequent metabolism of NO(3) (-).
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PMID:Nitrogen metabolism of soybeans: I. Effect of tungstate on nitrate utilization, nodulation, and growth. 1666 May 78

The main objectives of this work were to study the effect of different N sources on plant growth, N accumulation, and on the expression of nitrate reductase activity in Phaseolus vulgaris L. leaves. Plants were grown under greenhouse conditions (15 to 25 kilolux; 16/8 hour day/night cycles) in plastic pots filled with perlite: vermiculite (1:1) and watered daily with a minus N solution (N(2) plants) or supplemented with either KNO(3), (NH(4))(2)SO(4), or urea as combined N sources.Significant levels of nitrate reductase activity in trifoliolate leaves of N(2)-, NH(4) (+)-, urea-, or NO(3) (-)-dependent plants was demonstrated throughout this work. Leaves from the urea- or NH(4) (+)-grown plants accumulated NO(2) (-) in the dark but not in the light when NO(2) (-) was supplied by vacuum infiltration. These results indicated that the potential for reduction of NO(3) (-) or NO(2) (-) was not impaired by growing the plants on NH(4) (+) or urea and, in addition, provided evidence for the occurrence of a non-nitrate-inducible nitrite reductase. The nitrate reductase activities associated with N(2)-, NH(4) (+)-, or urea-dependent plants are tentatively regarded as ;constitutive' to differentiate from the widely occurring NO(3) (-)-inducible nitrate reductase activity.Plants grown on NO(3) (-) or urea accumulated significantly larger amounts of reduced N and dry matter as compared to NH(4) (+)- and N(2)-dependent plants. Regardless of N treatment, or size of plants, about 50% of the N accumulated by the plant was allocated to the leaves.
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PMID:Expression of Nitrate and Nitrite Reductase Activities under Various Forms of Nitrogen Nutrition in Phaseolus vulgaris L. 1666 85

The objectives of this study were to select and initially characterize mutants of soybean (Glycine max L. Merr. cv Williams) with decreased ability to reduce nitrate. Selection involved a chlorate screen of approximately 12,000 seedlings (progeny of mutagenized seed) and subsequent analyses for low nitrate reductase (LNR) activity. Three lines, designated LNR-2, LNR-3, and LNR-4, were selected by this procedure.In growth chamber studies, the fully expanded first trifoliolate leaf from NO(3) (-)-grown LNR-2, LNR-3, and LNR-4 plants had approximately 50% of the wild-type NR activity. Leaves from urea-grown LNR-2, LNR-3, and LNR-4 plants had no NR activity while leaves from comparable wild-type plants had considerable activity; the latter activity does not require the presence of NO(3) (-) in the nutrient solution for induction and on this basis is tentatively considered as a constitutive enzyme. Summation of constitutive (urea-grown wild-type plants) and inducible (NO(3) (-)-grown LNR-2, LNR-3, or LNR-4 plants) leaf NR activities approximated activity in leaves of NO(3) (-)-grown wild-type plants. Root NR activities were comparable in wild-type and mutant plants grown on NO(3) (-), and roots of both plant types lacked constitutive NR activity when grown on urea. In both growth chamber- and field-grown plants, oxides of nitrogen [NO((x))] were evolved from young leaves of wild-type plants, but not from leaves of LNR-2 plants, during in vivo NR assays. Analysis of leaves from different canopy locations showed that constitutive NR activity was confined to the youngest three fully expanded leaves of the wild-type plant and, therefore, on a total plant canopy basis, the NR activity of LNR-2 plants was approximately 75% that of wild-type plants. It is concluded that: (a) the NR activity in leaves of NO(3) (-)-grown wild-type plants includes both constitutive and inducible activity; (b) the missing NR activity in LNR-2, LNR-3, and LNR-4 leaves is the constitutive component; and (c) the constitutive NR activity is associated with NO((x)) evolution and occurs only in physiologically young leaves.
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PMID:Soybean mutants lacking constitutive nitrate reductase activity : I. Selection and initial plant characterization. 1666 32

Nitrogen assimilation in three nitrate reductase (NR) mutants of soybean (Glycine max L. Merr. cv Williams) was studied in the growth chamber and in the field. These mutants, LNR-2, LNR-3, and LNR-4, lack the non-NO(3) (-)-inducible or constitutive fraction of leaf NR activity found in wild-type plants, but this had no effect on the concentration of nitrogen accumulated when grown on NO(3) (-) in the growth chamber. Dry weight accumulation of two of the mutants (LNR-3 and LNR-4) was decreased relative to LNR-2 and wild type. In the field, LNR-2 had dry weights and nitrogen concentrations similar to the wild type at 34 and 61 days after planting, and at maturity. Acetylene reduction activities were also similar at 61 days.Urea-grown LNR-2 seedlings lack both inducible and constitutive NR activity, and were resistant to four days of treatment with 0.5 mm ClO(3) (-). Urea-grown wild-type seedlings, having only constitutive NR activity, developed ClO(3) (-) toxicity symptoms and suffered decreases in unifoliolate leaf NR activity and chlorophyll concentration. This suggests that (a) the reduction of ClO(3) (-) to ClO(2) (-) by NR is the major cause of ClO(3) (-) toxicity in soybeans and (b) the constitutive NR is active in situ.Segregation of the F(2) of reciprocal crosses between the wild type and the mutants indicated that absence of constitutive NR activity was controlled by a single recessive nuclear gene. Evolution of NO((x)) gas was also absent in these mutants, and this was found to be inherited jointly with constitutive NR activity: in 346 segregants, no recombinants were found. Allelism tests between LNR-2 and LNR-3, and LNR-2 and LNR-4, indicated that the constitutive NR mutation was at the same locus in each mutant.
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PMID:Soybean Mutants Lacking Constitutive Nitrate Reductase Activity : II. Nitrogen Assimilation, Chlorate Resistance, and Inheritance. 1666 33

NADH:nitrate reductase (EC 1.6.6.1) and NAD(P)H:nitrate reductase (EC 1.6.6.2) were purified from wild-type soybean (Glycine max [L.] Merr., cv Williams) and nr(1)-mutant soybean plants. Purification included Blue Sepharose- and hydroxylapatite-column chromatography using acetone powders from fully expanded unifoliolate leaves as the enzyme source.Two forms of constitutive nitrate reductase were sequentially eluted with NADPH and NADH from Blue Sepharose loaded with extract from wild-type plants grown on urea as sole nitrogen source. The form eluted with NADPH was designated c(1)NR, and the form eluted with NADH was designated c(2)NR. Nitrate-grown nr(1) mutant soybean plants yielded a NADH:nitrate reductase (designated iNR) when Blue Sepharose columns were eluted with NADH; NADPH failed to elute any NR form from Blue Sepharose loaded with this extract. Both c(1)NR and c(2)NR had similar pH optima of 6.5, sedimentation behavior (s(20,w) of 5.5-6.0), and electrophoretic mobility. However, c(1)NR was more active with NADPH than with NADH, while c(2)NR preferred NADH as electron donor. Apparent Michaelis constants for nitrate were 5 millimolar (c(1)NR) and 0.19 millimolar (c(2)NR). The iNR from the mutant had a pH optimum of 7.5, s(20,w) of 7.6, and was less mobile on polyacrylamide gels than c(1)NR and c(2)NR. The iNR preferred NADH over NADPH and had an apparent Michaelis constant of 0.13 millimolar for nitrate.Thus, wild-type soybean contains two forms of constitutive nitrate reductase, both differing in their physical properties from nitrate reductases common in higher plants. The inducible nitrate reductase form present in soybeans, however, appears to be similar to most substrateinduced nitrate reductases found in higher plants.
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PMID:Nitrate Reductases from Wild-Type and nr(1)-Mutant Soybean (Glycine max [L.] Merr.) Leaves : I. Purification, Kinetics, and Physical Properties. 1666 14

Two nitrate reductase deficient mutants of soybean (Glycine max [L.] Merr. cv Bragg) were isolated from approximately 10,000 M(2) seedlings, using a direct enzymic assay in microtiter plates. Stable inheritance of NR345 and NR328 phenotypes has been demonstrated through to the M(5) generation. Both mutants were affected in constitutive nitrate reductase activity. Assayable activities of cNR in nitrate-free grown seedlings was about 3 to 4% of the control for NR345 and 14 to 16% of the control for NR328. Both mutants expressed inducible NR during early plant development and were sensitive to nitrate and urea inhibition of nodulation. These new mutants will allow an extension of the characterization of nitrate reductases and their function in soybean. Preliminary evidence indicates that NR345 is similar to the previously isolated mutant nr(1), while NR328 is different.
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PMID:Isolation and Initial Characterization of Constitutive Nitrate Reductase-Deficient Mutants NR328 and NR345 of Soybean (Glycine max). 1666 58

Two nitrate reductase (NR) mutants were selected for low nitrate reductase (LNR) activity by in vivo NR microassays of M(2) seedlings derived from nitrosomethylurea-mutagenized soybean (Glycine max [L.] Merr. cv Williams) seeds. The mutants (LNR-5 and LNR-6) appeared to have normal nitrate-inducible NR activity. Both mutants, however, showed decreased NR activity in vivo and in vitro compared with the wild-type. In vitro FMNH(2)-dependent nitrate reduction and Cyt c reductase activity of nitrate-grown plants, and nitrogenous gas evolution during in vivo NR assays of urea-grown plants, were also decreased in the mutants. The latter observation was due to insufficient generation of nitrite substrate, rather than some inherent difference in enzyme between mutant and wild-type plants. When grown on urea, crude extracts of LNR-5 and LNR-6 lines had similar NADPH:NR activities to that of the wild type, but both mutants had very little NADH:NR activity, relative to the wild type. Blue Sepharose columns loaded with NR extract of urea-grown mutants and sequentially eluted with NADPH and NADH yielded a NADPH:NR peak only, while the wild-type yielded both NADPH: and NADH:NR peaks. Activity profiles confirmed the lack of constitutive NADH:NR in the mutants throughout development. The results provide additional support to our claim that wild-type soybean contains three NR isozymes, namely, constitutive NADPH:NR (c(1)NR), constitutive NADH:NR (c(2)NR), and nitrate-inducible NR (iNR).
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PMID:Biochemical Characterization of Soybean Mutants Lacking Constitutive NADH:Nitrate Reductase. 1666 62


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