Nitrate reductase

Federal government websites often end in. The site is secure. The nitrate anion is a simple, abundant and relatively stable species, yet plays a significant role in global cycling of nitrogen, nitrate reductase, global nitrate reductase change, and human health.

Nitrate reductase NR is the first enzyme of the nitrogen reduction pathway in plants, leading to the production of ammonia. However, in the nitrogen-fixing symbiosis between legumes and rhizobia, atmospheric nitrogen N 2 is directly reduced to ammonia by the bacterial nitrogenase, which questions the role of NR in symbiosis. Next to that, NR is the best-characterized source of nitric oxide NO in plants, and NO is known to be produced during the symbiosis. Moreover, NRs are involved together with the mitochondrial electron transfer chain in NO production throughout the symbiotic process and energy regeneration in N 2 -fixing nodules. Using an in vivo NMR spectrometric approach, we show that, in mature nodules, NRs participate also in the regulation of energy state, cytosolic pH, carbon and nitrogen metabolism under both normoxia and hypoxia.

Nitrate reductase

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Bacteria express nitrate reductases that produce nitrite, but mammals lack these specific enzymes. Here we report on nitrate reductase activity in rodent and human tissues that results in formation of nitrite and nitric oxide NO and is attenuated by the xanthine oxidoreductase inhibitor allopurinol. Nitrate administration to normoxic rats resulted in elevated levels of circulating nitrite that were again attenuated by allopurinol. Similar effects of nitrate were seen in endothelial NO synthase—deficient and germ-free mice, thereby excluding vascular NO synthase activation and bacteria as the source of nitrite. Nitrate pretreatment attenuated the increase in systemic blood pressure caused by NO synthase inhibition and enhanced blood flow during post-ischemic reperfusion. Our findings suggest a role for mammalian nitrate reduction in regulation of nitrite and NO homeostasis. This is a preview of subscription content, access via your institution.

However, under oxidative conditions, pyran ring scission has been observed in a pyran dithiolene molecule.

Werner M. Kaiser, Steven C. Assimilatory nitrate reductase NR of higher plants is a most interesting enzyme, both from its central function in plant primary metabolism and from the complex regulation of its expression and control of catalytic activity and degradation. It is also demonstrated that stress factors like nitrate deficiency and salinity have remarkably little direct influence on the NR activation state. Further, changes in NR activity measured in vitro are not always associated with changes in nitrate reduction rates in vivo , suggesting that NR can be under strong substrate limitation. However, it is not known whether the molecular form of NR in vivo affects its susceptibility to proteolytic degradation, or whether factors that affect the NR activation state also independently affect the activity or induction of the NR protease s. Accordingly, for many decades plant scientists have been engaged in elucidating the mechanism and regulation of nitrate uptake, transport and reduction in plants.

Nitrate NO 3 is a nitrogen-containing molecule that can be reduced by some bacterial species, but not others. Therefore, examining the ability of bacterial species to conduct nitrogen reduction is useful for characterizing and identifying bacterial species. Reduction of nitrate generally occurs during anaerobic respiration in which an organism derives its oxygen from nitrate to serve as the final electron acceptor to remove electrons from the electron transport chain. In some species, nitrate is reduced to nitrite leaving nitrite as evidence of the process:. In still other bacterial species, denitrification occurs where nitrate is reduced completely to N 2 gas and becomes largely unavailable to most living things as a nitrogen source:. Nitrate broth is used to determine if an organism can reduce nitrate. Some bacteria can reduce nitrate NO 3 to nitrite NO 2 by producing the enzyme nitrate reductase.

Nitrate reductase

Federal government websites often end in. The site is secure. Nitric oxide is a gaseous secondary messenger that is critical for proper cell signaling and plant survival when exposed to stress. Nitric oxide NO synthesis in plants, under standard phototrophic oxygenic conditions, has long been a very controversial issue.

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Biochemistry 42 , — Table 1 Biogenic processes involved in the nitrogen cycle. Journal of Experimental Botany 51 , — Nar, the classical respiratory NR, couples nitrate respiration to proton translocation across the cytoplasmic membrane of bacteria. The g -factor falls within a narrow range of 1. Its function is not clear. Tungstate: is it really a specific nitrate reductase inhibitor in plant nitric oxide research? It is also demonstrated that stress factors like nitrate deficiency and salinity have remarkably little direct influence on the NR activation state. The protein structure of E. You have entered an invalid code. Download as PDF Printable version.

Nitrite reductase refers to any of several classes of enzymes that catalyze the reduction of nitrite.

Considered together, these results indicate that 1 both the NR and the mitochondrial ETC are involved in the production of NO, probably via the reduction of nitrate to nitrite by NR and the subsequent reduction of nitrite to NO at the mitochondrial ETC level, and 2 NR activity is linked to energy regeneration processes in mature nodules, but not during the first steps of the symbiosis. Kolbert, Z. EC number Enzyme superfamily Enzyme family List of enzymes. The response to nitric oxide of the nitrogen-fixing symbiont Sinorhizobium meliloti. Journal of Health Science. Although it has been known for quite some time that nitrate is an important species environmentally, recent studies have identified potential medical applications. Search Search articles by subject, keyword or author. The crystal structure of the recombinant Haemophilus influenza NapB has revealed that the two heme molecules are stacked parallel and hydrogen bonded to each other via propionic acid side chains. Then the Mo d-orbital electrons flip over, creating a multiple bond between Mo VI and that oxygen, ejecting nitrite. Long term studies with a continuous supply of nitrate. Silveira, J. Moderate hypoxia induces xanthine oxidoreductase activity in arterial endothelial cells. Leghemoglobin green derivatives with nitrated hemes evidence production of highly reactive nitrogen species during aging of legume nodules. Simon J. Under anoxia, where NR was stabilized and active, sucrose levels decreased, yet at the same time hexose levels increased drastically Fig.