scholarly journals Nitrate Fluxes and Nitrate Reductase Activity of Suspension-Cultured Tobacco Cells (Effects of Internal and External Nitrate Concentrations)

1993 ◽  
Vol 102 (3) ◽  
pp. 851-857 ◽  
Author(s):  
N. Zhang ◽  
C. T. MacKown
Keyword(s):  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Tobacco Cells ◽  
Nitrate Concentrations

Effect of carbon and nitrogen metabolism on nitrate reductase activity of Rhodobacter capsulatus E1F1

1994 ◽  
Vol 40 (8) ◽  
pp. 645-650 ◽  
Author(s):  
María M. Dobao ◽  
Manuel Martínez-Luque ◽  
Conrado Moreno-Vivián ◽  
Francisco Castillo
Keyword(s):  
Nitrate Reductase ◽  
Nitrogen Metabolism ◽  
Nitrogen Balance ◽  
Nitrate Reductase Activity ◽  
Rhodobacter Capsulatus ◽  
Reductase Activity ◽  
Intracellular Concentration ◽  
Carbon And Nitrogen ◽  
Nitrate Concentrations ◽  
Carbon And Nitrogen Metabolism

The phototrophic bacterium Rhodobacter capsulatus E1F1 possesses an assimilatory, inducible nitrate reductase that is regulated by carbon and nitrogen metabolism. Nitrate reductase activity was detected in cells cultured with amino acids and nitrate as simultaneous nitrogen source but it required an additional carbon source such as D,L-malate. A significant rise in nitrate reductase activity was observed in media with increasing nitrate concentrations up to 10 mM KNO3, although higher nitrate concentrations had an inhibitory effect. Growth yield, generation time, and nitrate reductase activity were also dependent on the concentration of D,L-malate in cells growing with 10 mM nitrate. In carbon-starved cells, nitrate reductase activity dropped even in the presence of nitrate. The intracellular concentration of keto acids such as oxaloacetate or 2-oxoglutarate fluctuated widely depending on the presence of nitrogen and carbon sources in the culture medium. The increase in the intracellular concentration of oxaloacetate or 2-oxoglutarate in R. capsulatus E1F1 correlated well with a rise in nitrate reductase activity. These results suggest that the intracellular carbon–nitrogen balance regulates nitrate uptake in R. capsulatus E1F1, thus affecting the expression of nitrate reductase.Key words: carbon–nitrogen balance, nitrate reductase, Rhodobacter capsulatus.

scholarly journals Periplasmic Nitrate Reductase (NapABC Enzyme) Supports Anaerobic Respiration by Escherichia coli K-12

2002 ◽  
Vol 184 (5) ◽  
pp. 1314-1323 ◽  
Author(s):  
Valley Stewart ◽  
Yiran Lu ◽  
Andrew J. Darwin
Keyword(s):  
Escherichia Coli ◽  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Anaerobic Respiration ◽  
Null Alleles ◽  
E Coli ◽  
Periplasmic Nitrate Reductase ◽  
Nitrate Concentrations ◽  
K 12

ABSTRACT Periplasmic nitrate reductase (NapABC enzyme) has been characterized from a variety of proteobacteria, especially Paracoccus pantotrophus. Whole-genome sequencing of Escherichia coli revealed the structural genes napFDAGHBC, which encode NapABC enzyme and associated electron transfer components. E. coli also expresses two membrane-bound proton-translocating nitrate reductases, encoded by the narGHJI and narZYWV operons. We measured reduced viologen-dependent nitrate reductase activity in a series of strains with combinations of nar and nap null alleles. The napF operon-encoded nitrate reductase activity was not sensitive to azide, as shown previously for the P. pantotrophus NapA enzyme. A strain carrying null alleles of narG and narZ grew exponentially on glycerol with nitrate as the respiratory oxidant (anaerobic respiration), whereas a strain also carrying a null allele of napA did not. By contrast, the presence of napA+ had no influence on the more rapid growth of narG+ strains. These results indicate that periplasmic nitrate reductase, like fumarate reductase, can function in anaerobic respiration but does not constitute a site for generating proton motive force. The time course of Φ(napF-lacZ) expression during growth in batch culture displayed a complex pattern in response to the dynamic nitrate/nitrite ratio. Our results are consistent with the observation that Φ(napF-lacZ) is expressed preferentially at relatively low nitrate concentrations in continuous cultures (H. Wang, C.-P. Tseng, and R. P. Gunsalus, J. Bacteriol. 181:5303-5308, 1999). This finding and other considerations support the hypothesis that NapABC enzyme may function in E. coli when low nitrate concentrations limit the bioenergetic efficiency of nitrate respiration via NarGHI enzyme.

Nitrate Reductase Activity of Maize Hybrids and Their Parental Inbred 1

Crop Science ◽  
1966 ◽  
Vol 6 (2) ◽  
pp. 169-173 ◽  
Author(s):  
L. E. Schrader ◽  
D. M. Peterson ◽  
E. R. Leng ◽  
R. H. Hageman
Keyword(s):  
Nitrate Reductase ◽  
Nitrate Reductase Activity ◽  
Reductase Activity ◽  
Maize Hybrids ◽  
Parental Inbred
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