Nitrate reductases and

It is not clear why some organisms have two 14-3-3 isoforms while others have up to 12. Binding 14-3-3 inhibits the plant enzyme nitrate reductase and there appears to be no selectivity between plant 14-3-3 isoforms in fact yeast and human isoforms appear to work equally as well in vitro. The best example where selectivity has been demonstrated is human 14-3-3o. 14-3-3o Preferential homodimerizes with itself and crystallization revealed a structural basis for this isoform s dimerization properties as well as for its specific selectivity for target binding proteins. Here partner specificity is the result of amino acid differences outside of the phosphopeptide-binding cleft. 

There are four different classes of nitrate reductases (234). The nitrate reductases from D. desulfuricans show a strong homology to the a-subunit of the class of periplasmic respiratory nitrate reductases, and also to some of the enzymes that are included on the class of cytoplasmic assimilatory nitrate reductases. Because of this fact, a proposal was made for a new class of monomeric NAP, which contains the minimal arrangement of metal centers to perform nitrate reduction one [4Fe-4S] cluster and a Mo bound to two MGD. 

Fig. 6. Representative EPR spectra displayed by trinuclear and tetranucleEir iron-sulfur centers, (a) and (b) [3Fe-4S] + center in the NarH subunit of Escherichia coli nitrate reductase and the Ni-Fe hydrogenase fromD. gigas, respectively, (c) [4Fe-4S] + center in D. desulfuricans Norway ferredoxin I. (d) [4Fe-4S] center in Thiobacillus ferrooxidans ferredoxin. Experimental conditions temperature, 15 K microwave frequency, 9.330 GHz microwave power, (a) 100 mW, (b) 0.04 mW, (c) smd (d) 0.5 mW modulation amplitude (a), (c), (d) 0.5 mT, (b) 0.1 mT.

Kroneck PMH, Aht DJ (2002) Molybdenum in nitrate reductase and nitrite oxidoreductase. In Molybdenum and Tungsten- Their Roles in Biological Processes. Sigel A, Sigel H (eds) Marcel Dekker, Inc., New York, 369-403... 

The recognition that the Mo in the molybdoproteins exists in organic cofactor forms came from studies of mutants of Aspergillus and Neurospora.650 In 1964, Pateman and associates discovered mutants that lacked both nitrate reductase and xanthine dehydrogenase. Later, it was shown that acid-treated molybdoenzymes released a material that would restore activity to the inactived nitrate reductase from the mutant organisms. This new coenzyme, a phosphate ester of molybdopterin (Fig. 15-17), was characterized by Rajagopalan and coworkers.650 651 A more complex form of the coenzyme, molybdopterin cytosine dinucleotide... 

Campbell, W.H. (1988). Nitrate reductase and its role in nitrate assimilation in plants. Physiologia Plantarum 74, 214-19. 

Campbell, W.H. Kinghom, J.R. (1990). Functional domains of assimilatory nitrate reductases and nitrite reductases. Trends in Biochemistry 15, 315-19. 

Campbell, W.H. Redinbaugh, M.G. (1984). Ferric-citrate reductase activity of nitrate reductase and its role in iron assimilation by plants. Journal of Plant Nutrition 7, 799-806. 

Gowri, G. Campbell, W.H. (1989). cDNA clones for corn leaf NAD-H nitrate reductase and chloroplast NAD(P)+ glyceraldehyde-3-phosphate dehydrogenase. Characterization of the clones and analysis of the expression of the genes in leaves as influenced by nitrate in the light and dark. Plant Physiology 90, 792-8. 

Hageman, R.H., Flesher, D. Gitter, A. (1961). Diurnal variation and other light effects influencing the activity of nitrate reductase and nitrogen metabolism in corn. Crop Science 1, 201-4. 

Hyde, G.E. Campbell, W.H. (1990). High-level expression in Escherichia coli of the catalytically active flavin domain of corn leaf NADH-nitrate, reductase and its comparison to human NADH-cytochrome b5 reductase. Biochemical and Biophysical Research Communications 168, 1285-91. 

Rajasekhar, V.K. Oelmiiller, R. (1987). Regulation of nitrate reductase and nitrite reductase in higher plants. Physiologia Plantarum 71, 517-21. 

Sharma, A.K. Sopory, S.K. (1984) Independent effects of phytochrome and nitrate on nitrate reductase and nitrite reductase activities in maize. Photochemistry and Photobiology 39, 491-3. 

Small, I.S. Wray, J.L. (1980). NADH nitrate reductase and related NADH cytochrome c reductase species in barley. Phytochemistry 19, 387-94. 

It is the (MPT)Mo(0)2 cofactor variant that likely reconstitutes the nitrate reductase activity in the Nit-1 mutant [29,31], Although the (MPT)Mo(0)2 unit could be provided directly by sulfite oxidase, nitrate reductase, and even xanthine... 

From an analysis of their protein sequences, dmso reductase, respiratory nitrate reductase, and formate dehydrogenase (FDH) are assigned as members of a large... 

Similar mechanisms operate in the action of nitrate reductase and nitrite reductase. Both of these substances are produced from ammonia by oxidation. Plants and soil bacteria can reduce these compounds to provide ammonia for metabolism. The common agricultural fertilizer ammonium nitrate, NH4NO3, provides reduced nitrogen for plant growth directly, and by providing a substrate for nitrate reduction. NADH or NADPH is the electron donor for nitrate reductase, depending on the organism. 

Packard, T.T. (1979) Half-saturation constants for nitrate reductase and nitrate translocation in marine phytoplankton. Deep Sea Res. 26, 321-326. 

Nitrate Reductase Activity. There are similarities between induced nitrate reductase activity and induced iron stress response. In both, biochemical reactions are induced, and a substrate is reduced N03 to N02 by nitrate reductase and Fe3+ to Fe2+ by a reductant activated in response to iron stress. Chemical reactions induced by iron stress increased the use of iron, and simultaneously increased nitrate reductase activity in roots (Figure 5) and in tops of iron-efficient tomato. This induced nitrate reductase activity declined when iron was made available to the plants. 

Compared with other transition metals in biological redox systems, the oxidation states likely to be used by molybdenum are very high (74). As discussed previously, the IV, V, and VI states are a likely set of participants in molybdenum oxidases, and while the II and III states remain viable for molybdenum reductases, it nevertheless seems likely that higher oxidation states will be found in these enzymes as well. Indeed, the substitution of tungsten for molybdenum in both nitrate reductase and nitrogenase indicates this likelihood as it is much more difficult to obtain the lower oxidation states of tungsten. 

The assimilatory enzyme from the mold Neurospora crassa has been intensively studied for over two decades, particularly by Nason and his collaborators. Thus, Nason and Evans (39) identified FAD as a prosthetic group in the enzyme Nicholas, Nason, and McElroy (40) showed that molybdenum was required for the synthesis of nitrate reductase Nicholas and Nason (41) suggested its presence in the enzyme Garrett and Nason (42) showed that a b-type cytochrome (cytochrome 6557) co-purifies with this nitrate reductase and Nason et al. (11) suggested, from in vitro complementation experiments with nitrate reductaseless mutants, that the enzyme consists of at least two components required for activity. These workers have suggested that the electron transfer pathway is ... 

Athwal, G. S., Huber, J. L., and Huber, S. C., 1998, Phosphorylated nitrate reductase and 14-3-3 proteins. Plant Physiol. 118 1041nl048. 

Blasco, F., lobbi, C., Ratouchniak, J., Bonnefoy, V., and Chippaux, M., 1990, Nitrate reductases of Escherichia coli. sequence of the second nitrate reductase and comparison with that encoded by the narGHJI operon. Mol. Gen. Genet. 222 104nlll. 

---