Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:1.7.1.4 (nitrite reductase)
1,847 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The dark and light reduction of nitrate and nitrite by cell-free preparations of the blue-green alga Anacystis nidulans has been investigated. The three following methods have been successfully applied to the preparation of active particulate fractions from the alga cells: (a) shaking with glass beads, (b) lysozyme treatment and lysis of the resulting protoplasts, and (c) sonication. The two enzymes of the nitrate-reducing system-namely, nitrate reductase and nitrite reductase-are firmly bound to the isolated pigment-containing particles, and can be easily solubilized by prolonging the vibration or sonication time. Both enzymes-whether solubilized or bound to the particles-depend on reduced ferredoxin as the immediate electron donor. In its presence, the alga particles catalyze the gradual photoreduction of nitrate to nitrite and ammonia, a process that can thus be considered as one of the most simple and relevant examples of Photosynthesis. Some of the properties of nitrate reductase have been studied. Nitrate reductase as well as nitrite reductase are adaptive enzymes repressed by ammonia.
...
PMID:Ferredoxin-dependent photosynthetic reduction of nitrate and nitrite by particles of Anacystis nidulans. 0 27

It had previously been held that chlorate is not itself toxic, but is rendered toxic as a result of nitrate reductase-catalysed conversion to chlorite. This however cannot be the explanation of chlorate toxicity in Aspergillus nidulans, even though nitrate reductase is known to have chlorate reductase activity. Among other evidence against the classical theory for the mechanism of chlorate toxicity, is the finding that not all mutants lacking nitrate reductase are clorate resistant. Both chlorate-sensitive and resistant mutants lacking nitrate reductase, also lack chlorate reductase. Data is presented which implicates not only nitrate reductase but also the product of the nirA gene, a positive regulator gene for nitrate assimilation, in the mediation of chlorate toxicity. Alternative mechanisms for chlorate toxicity are considered. It is unlikely that chlorate toxicity results from the involvement of nitrate reductase and the nirA gene product in the regulation either of nitrite reductase, or of the pentose phosphate pathway. Although low pH has an effect similar to chlorate, chorate is not likely to be toxic because it lowers the pH; low pH and chlorate may instead have similar effects. A possible explanation for chlorate toxicity is that it mimics nitrate in mediating, via nitrate reductase and the nirA gene product, a shut-down of nitrogen catabolism. As chlorate cannot act as a nitrogen source, nitrogen starvation ensues.
...
PMID:Chlorate toxicity in Aspergillus nidulans. Studies of mutants altered in nitrate assimilation. 0 97

Optimal cell yield of Pseudomonas aeruginosa grown under denitrifying conditions was obtained with 100 mM nitrate as the terminal electron acceptor, irrespective of the medium used. Nitrite as the terminal electron acceptor supported poor denitrifying growth when concentrations of less than 15 mM, but not higher, were used, apparently owing to toxicity exerted by nitrite. Nitrite accumulated in the medium during early exponential phase when nitrate was the terminal electron acceptor and then decreased to extinction before midexponential phase. The maximal rate of glucose and gluconate transport was supported by 1 mM nitrate or nitrite as the terminal electron acceptor under anaerobic conditions. The transport rate was greater with nitrate than with nitrite as the terminal electron acceptor, but the greatest transport rate was observed under aerobic conditions with oxygen as the terminal electron acceptor. When P. aeruginosa was inoculated into a denitrifying environment, nitrate reductase was detected after 3 h of incubation, nitrite reductase was detected after another 4 h of incubation, and maximal nitrate and nitrite reductase activities peaked together during midexponential phase. The latter coincided with maximal glucose transport activity.
...
PMID:Denitrifying Pseudomonas aeruginosa: some parameters of growth and active transport. 10 56

The Neurospora crassa assimilatory nitrite reductase (EC 1.6.6.4) catalyzes the NADPH-dependent reduction of nitrite to ammonia, a 6-electron transfer reaction. Highly purified preparations of this enzyme exhibit absorption spectra which suggest the presence of a heme component (wavelength maxima for oxidized senzyme: 390 and 578 nm). There is a close correspondence between nitrite reductase activity and absorbance at 400 nm when partially purified nitrite reductase preparations are subjected to sucrose gradient centrifugation. In addition, a role for an iron component in the formation of active nitrite reductase is indicated by the fact that nitrate-induced production of nitrite reductase activity in Neurospora mycelia in vivo requires the presence of iron in the induction medium. The heme chromophore present in Neurospora nitrite reductase preparations is reducible by NADPH. Complete reduction, however, requires the presence of added FAD. The NADPH-nitrite reductase activity of the enzyme is also dependent upon addition of FAD. A spectrally unique complex is formed between the heme chromophore and nitrite (or a reduction product thereof) when nitrite is added to NADPH-reducted enzyme. Carbon monoxide forms a complex with the heme chromophore of nitrite reductase with an intense alpha-band maximum at 590 nm and a beta-band of lower intensity at 550 nm. CO is an inhibitor of NADPH-nitrite reductase activity. Spectrophotometrically detectable CO complex formation and Co inhibition of enzyme activity share the following properties...
...
PMID:Siroheme: a prosthetic group of the Neurospora crassa assimilatory nitrite reductase. 12 95

One allele at each of the five nit loci in Neurospora crassa together with the wild type strain have been compared on various nitrogen sources with regard to (i) their growth characteristics (ii) the level of nitrate reductase and its associated activities (reduced benzyl viologen nitrate reductase and cytochrome c reductase) (iii) the level of nitrate reductase and (iv) their ability to take up nitrite from the surrounding medium. Results are consistent with the hypothesis that nit-3 is the structural gene for nitrate reductase, nit-1 specifies in part of molybdenum containing moiety which is responsible for the nit-3 gene product dimerising to form nitrate reductase, nit-4 and nit-5 are regulator genes whose products are involved in the induction of both nitrate reductase and nitrite reductase and nit-2 codes for a generalised ammonium activated repressor protein. Studies on the induction of nitrate reductase (and its associated activities) and nitrite reductase in wild type, nit-1 and nit-3 in the presence of either nitrate or nitrite suggest that each enzyme may be regulated independently of the other and that nitrite could be true co-inducer of the assimilatory pathway. Nitrite uptake experiments with nit-2, nit-4 and nit-5 strains show that whereas nit-4 and nit-5 are freely permeable to this molecule, it is unable to enter the nit-2 mycelium.
...
PMID:Biochemical studies on the nit mutants of Neurospora crassa. 13 3

Cytochrome c552, which has been implicated as an electron carrier for nitrite reduction by Escherichia coli, has been separated from NADH-nitrite oxidoreductase activity. The cytochrome is therefore not required for the reduction of nitrite by NADH in vitro. Nevertheless, some mutants which were selected by their inability to use nitrite as a nitrogen source during anaerobic growth synthesize neither NADH-nitrite oxidoreductase nor cytochrome c552. The defects in these mutants are due to mutations in a single gene, nirA, which is located at about minute 29 on the recalibrated linkage map. Experiments with an F' plasmid which carries a nirA+ allele established that nirA+ is dominant to the defective allele. Other mutants, defective in nitrate reductase activity because of mutations in the chlA or chlB genes, synthesized nitrite reductase and cytochrome c552 in the absence of nitrate or nitrite. A mutant with a defective fnr gene was also NirA- and, conversely, nirA mutants were Fnr-. In a series of transduction experiments, attempts to separate the nirA and fnr defects were unsuccessful. Furthermore, no complementation was observed when an F' plasmid carrying a defective nirA allele was transferred into the fnr strain. It is concluded that the fnr gene described by Lambden & Guest (1976) is identical to the nirA gene and that its product affects the synthesis or assembly of a variety of anaerobic redox enzymes which include nitrite reductase, cytochrome c552, nitrate reductase, fumarate reductase and formate hydrogenlyase.
...
PMID:The chromosomal location and pleiotropic effects of mutations of the nirA+ gene of Escherichia coli K12: the essential role of nirA+ in nitrite reduction and in other anaerobic redox reactions. 20 51

Previous work (Rand and Arst, 1977) led to the proposal that the nis-5 mutation results in a new low activity promoter for niiA, the structural gene for nitrite reductase in Aspergillus nidulans. Expression of niiA via this promoter differs from expression of niiA via its normal promoter/initiator in that expression by the new promoter is not subject to nitrate induction or ammonium repression. nis-5 reduces but does not abolish niiA expression mediated by the normal promoter/initiator. In this work we show that nis-5 is associated with and is probably identical to a non-reciprocal translocation in which a considerable portion of the centromere proximal region of the right arm of linkage group II is inserted into linkage group VIII between niiA and niaD, the tightly linked, probably contiguous structural genes for nitrate reductase. This implies that niiA, along with its normal promots yet unidentified by its normal role. Further, it indicates that niiA is transcribed from the niaD-proximal side. As niiA and niaD are separated by a large number of unrelated genes in nis-5 strains, we can safely conclude that expression of niiA does not occur solely by synthesis of a messenger which carries a niaD as well as a niiA transcript. Clearly, niiA and niaD do not form an operon for which a di- (or poly-) cistronic messenger by the only transcript. This is consistent with other experimental evidence which shows that the syntheses of nitrate and nitrite reductases are not coordinately regulated. Nevertheless, all of these data would also be consistent with a model in which niiA and niaD form an operon-type structure having overlapping transcripts, one being di- (or poly-) cistronic and including both niiA and niaD and another being monocistronic for niiA. The reduced niiA expression mediated by the normal promoter/initiator in nis-5 strains could be a consequence of the functioning or positioning of the new linkage group II niiA promoter. An alternative, but not mutually exclusive, explanation would be that the insertional translocation prevents synthesis of a niiA niaD dicistronic transcript so that only that component of niiA expression which is due to a monocistronic niiA messenger can be induced by nitrate (and nitrite) in nis-5 strains. The apparently low activity of the new linkage group II promoter in comparison to the normal niiA promoter/initiator might betoken considerable efficiency of the latter rather than any particular lack of efficiency of the former. In addition, this work has involved extensive new mapping in linkage group II, including both mitotic mapping of the centromere and meiotic mapping of previously unlocated markers. A series of crosses in cluding genotype combinations both heterozygous and homozygous for nis-5 has been used to map the break-points and orientation of the translocation. As one break-point is closer to the centromere of linkage group II than the most centromere proximal identified gene on the same (i.e...
...
PMID:Do the tightly linked structural genes for nitrate and nitrite reductases in Aspergillus nidulans form an operon? Evidence from an insertional translocation which separates them. 38 64

At dissolved oxygen tensions of 15 mmHg (2 kPa) and below, nitrate-limited continuous cultures of Klebsiella K312 synthesized nitrate reductase (NR) and nitrite reductase (NiR) and excreted ammonia. Under anaerobic conditions over 60% of the nitrate-nitrogen utilized was excreted as ammonia. In contrast, carbon-limited cultures excreted nitrite at dissolved oxygen tensions of 15 mmHg or below and synthesized NR but not NiR. Ammonia repressed neither NR nor NiR synthesis. These observations indicate that below a critical oxygen tension of 15 mmHg Klebsiella K312 utilizes oxygen and nitrate as electron acceptors. This oxygen tension correlates well with the critical oxygen tension observed for a change from oxidative to fermentative metabolism in cultures of Klebsiella aerogenes. The product of dissimilatory nitrate reduction is ammonia in nitrate-limited cultures but principally nitrite in carbon-limited (nitrate excess) cultures.
...
PMID:Influence of oxygen tension on nitrate reduction by a Klebsiella sp. growing in chemostat culture. 47 38

Seventeen strains of the new species Bacillus azotoformans were isolated by enrichment culture in peptone broth inoculated with pasteurized soil and then incubated under N2O at 32 degrees C. The bacterium is a Gram-negative rod, motile with peritrichous flagella, which produces oval spores without exosporia in swollen sporangia. However, the cells have thick walls, mesosomes, and persistent septa characteristic of Gram-positive bacteria. The bacterium lacks fermentative activity, does not attack carbohydrates, has complex growth requirements, and will grow anaerobically only if one of the following electron acceptors is present: NO3-, NO2-, N2O, S4O6--, or fumarate. Nitrate, nitrite, and nitrous oxide are denitrified with the production of N2. The microorganism is mesophilic, gives a positive oxidase reaction, synthesizes a type c cytochrome, and does not hydrolyse gelatin, starch, or "Tween 80." Poly-beta-hydroxybutyric acid is snythesized when the bacterium is grown in a medium containing DL-3-hydroxybutyrate. The following enzymes are present: nitrate reductase A, respiratory nitrite reductase, tetrathionate and fumarate reductases, and L-glutamate dehydrogenase. The following enzymes are absent: thiosulfate reductase, urease, lecithinase, arginine dihydrolase, phenylalanine deaminase, and catalase. For the 17 strains, the mean value of the G = C percent of the DNA is 39.8 +/- 1.2. All the strains are highly similar.
...
PMID:[Morphological, physiological and taxonomic studies of Bacillus azotoformans]. 65 12

Chlorate resistant spontaneous mutants of Azospirillum spp. (syn. Spirillum lipoferum) were selected in oxygen limited, deep agar tubes with chlorate. Among 20 mutants from A. brasilense and 13 from A. lipoferum all retained their functional nitrogenase and 11 from each species were nitrate reductase negative (nr-). Most of the mutants were also nitrite reductase negative (nir-), only 3 remaining nir+. Two mutants from nr+ nir+ parent strains lost only nir and became like the nr+ nir- parent strain of A. brasilense. No parent strain or nr+ mutant showed any nitrogenase activity with 10 mM NO3-. In all nr- mutants, nitrogenase was unaffected by 10 mM NO3-. Nitrite inhibited nitrogenase activity of all parent strains and mutants including those which were nir-. It seems therefore, that inhibition of nitrogenase by nitrate is dependent on nitrate reduction. Under aerobic conditions, where nitrogenase activity is inhibited by oxygen, nitrate could be used as sole nitrogen source for growth of the parent strains and one mutant (nr- nir-) and nitritite of the parent strains and 10 mutants (all types). This indicates the loss of both assimilatory and dissimilatory nitrate reduction but only dissimilatory nitrite reduction in the mutants selected with chlorate.
...
PMID:Nitrate and nitrite reductase negative mutants of N2-fixing Azospirillum spp. 69 99


1 2 3 4 5 6 7 8 9 10 Next >>

---