Nitrite reductase regulation

Faure, J.D., Vincentz, M., Kronenberger, J. Caboche, M. (1991). Co-regulated expression of nitrate and nitrite reductases. The Plant Journal 1, 107-13. 

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

Suzuki, I., Sugiyama, T., and Omata, T. (1993). Primary structure and transcriptional regulation of the gene for nitrite reductase from the cyanobacterium Synechococcus PCC 7942. Plant Cell Physiol. 34, 1311-1320. 

Stewart, V. (1994). Regulation of nitrate and nitrite reductase synthesis in enterobacteria. Antonie van Leeuwenhoek 66, 37-45. 

Each step of the denitrification pathway is catalyzed by a distinct enzyme, nitrogen oxide reductase (nitrate reductase, nitrite reductase, nitric oxide reductase, and nitrous oxide reductase), that transfers electrons from the chain to the particular intermediate. Thermodynamically, in the absence of oxygen, nitrogen oxides are the most preferred electron acceptors by facultative bacterial groups. The role of nitrogen oxides in regulating organic matter decomposition has been discussed in earlier chapters (see Chapter 5). 

In nitrite-ammonifying bacteria, especially in enterobacteria, there may exist two independently regulated dissimilatory ways of nitrite reduction to ammonia with two different physiological functions [125]. A cytoplasmic siroheme-dependent nitrite reductase activity (NADH nitrite oxidoreductase) [138,139] confers on... 

Table 1 collects selected metric parameters and IR stretching frequencies (wno) fot a representative set of six-coordinated (6C) complexes of iron, ruthenium, and osmium, and few iron 5C-compounds. A number of Fe(III) heme proteins are involved in the regulation of the NO biosynthesis by the enzyme NO synthase, in NO transport (as vasodilator) in nitrophorins and in NO inhibition processes of cytochrome P450 and related enzymes (45). Heme enzymes are also intermediates in cyt cd nitrite reductases (NIRs), (46) and in NO reduction by a fungal cyt P450 NO reductase (47). The nonheme Fe(III) nitrile hydratase enzyme (NHase) is relevant to the microbial assimilation of organic nitriles, using... 

Nitrite reductase is regulated by nitrate and light in a manner similar to NR. Nitrite reductase activity increases in response to nitrate or nitrite (Ingle et al. 

Kramer etfl/., 1989 Wvalle eta/., 1989). Nitrite reductase mRNA was present in small amounts in uninduced leaves of both species but not in roots of maize. Induction by nitrate increased the NiR mRNA in both species and in both the roots and leaves of maize. Perhaps one of the two NiR genes present in maize is expressed constitutively in leaves (Kramer et al., 1989). The NiR mRNA induction pattern in maize (Kramer et al., 1989) is similar to the NR mRNA induction pattern in barley (Melzer et al., 1989). Nitrite reductase mRNA is rapidly induced by nitrate, reaching a peak within 5 hr and then declining to a lower level even in the presence of continued nitrate. The NiR mRNA appears to be short lived with a half-life as short as 30 min (Kramer et al, 1989). The mechanisms regulating these fluctuations in NiR mRNA are not known at this time. Nitrite was capable of limited induction of NiR mRNA in spinach leaves (Back etal, 1988), although the role of nitrite is equivocal due to Ae possibility of in vivo oxidation of nitrite to nitrate (Aslam et al, 1987). 

The reduction of nitrate to ammonia is a rather simple chemical process under very complex control in biological systems. In higher plants the assimilation of nitrate involves the acquisition and subsequent reduction of nitrate to ammonia by nitrate and nitrite reductase. Although our understanding of the biochemistry, genetics, and molecular aspects of nitrate assimilation has advanced, a great deal remains to be learned, especially about regulation and... 

Organism Sensor kinase Response regulator Nitrite exclusion a n 5 y Nitrate reductase large small Nitrite transporter... 

Costa, C., Macedo, A., Moura, 1., Moura, j. j. G., LeGall, J., Berber, Y., Liu, M.-Y., and Payne, W. J. (1990). Regulation of the hexaheme nitrite/nitric oxide reductase of Desulfovibrio desulfuricans, Wohnella succinogenes, and Escherichia coli. A mass spectro-metric study. FEBS Lett. 276, 67-70. 

The opposite sequence, reduction of nitrate and nitrite ions, provides a major route of acquisition of ammonia for incorporation into cells by bacteria, fungi, and green plants (Fig. 24-1). Assimilatoiy (biosynthetic) nitrate reductases catalyze the two-electron reduction of nitrate to nitrite (Eq. 16-61). This is thought to occur at the molybdenum atom of the large 900-residue highly regulated molybdopterin-dependent enzyme. In green plants the reductant is... 

Nitrate reductase is an inducible enzyme and is usually found only in the presence of nitrate. Nitrate reductase is the logical point to effect regulation of the input of reduced nitrogen for the plant because it is the first and normally the rate limiting enzyme between nitrate and amino-N. The toxic effects of excess levels of nitrite and ammonium ions also indicate the desirability of regulating their production. 

In addition to the substrate, nitrate, regulating the production of nitrate reductase, it has been reported that in some instances the product nitrite can stimulate the appearance of nitrate reductase (Ingle et al., 1966 Kaplan cr al., 1978). The aromatic nitro compound, chloramphenicol, and other organic nitro compounds have been shown to regulate the level of nitrate reductase in rice seedling (Shen, 1972a,b). Not only is the level of nitrate reductase influenced by these compounds but the nucleotide specificity is changed in favor of NADPH. 

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