Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.7.1.2 (nitrate reductase)
 3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nitrate reductase, released and purified from membrane fractions of Escherichia coli, is composed of three subunits. Formation of the enzyme depends on induction of the nar operon, narGHJI, which is composed of four open reading frames (ORF). Previous studies established that the first two genes in the operon narG and narH encode the alpha and beta subunits, respectively, while formation of the gamma subunit, cytochrome bNR, depends on expression of the promoter distal genes. The narJ and narI genes were subcloned separately into plasmids where each was under the control of the nar promoter. Expression of these plasmids in a mutant which forms only alpha and beta subunits revealed that expression of the narI gene is sufficient to restore normal levels of cytochrome bNR, but expression of both genes is required for assembly of fully active, membrane-bound nitrate reductase. The amino acid composition, the N-terminal sequence, and the sequence of cyanogen bromide fragments derived from the isolated gamma subunit corresponds to that expected for a protein produced by the narI ORF. A protein corresponding to the narJ ORF did not appear to be associated with the purified nitrate reductase complex or with the complex immunoprecipitated from Triton X-100-solubilized membrane preparations. We conclude that narI encodes the gamma subunit (cytochrome bNR) and that while the product of the narJ gene is required for assembly of fully active membrane-bound enzyme it is not tightly associated with the active enzyme.
 ...
PMID:Roles of the narJ and narI gene products in the expression of nitrate reductase in Escherichia coli. 305 88

The concentration of apparent total N-nitroso compounds (ATNC) in beer has been investigated using a group-selective procedure based on chemical denitrosation with hydrogen bromide and chemiluminescence detection of the released nitric oxide. In a survey of samples of 40 brands of beer and lager, detectable levels of ATNC were present in 17 samples at concentrations of 20-100 micrograms N-NO/kg in 11 and 100-500 micrograms N-NO/kg in six. To determine the origin of ATNC in beer the production of a commercial batch was examined in detail. ATNC levels were below the detection limit in the sweet wort (aqueous extract of malt), bitter wort (malt extract boiled with hops) and also at the start of fermentation, but during the course of fermentation the concentration of ATNC increased appreciably and that of inorganic nitrate decreased; detectable, though transitory, levels of inorganic nitrite were observed. None of the brewing ingredients contained sufficiently high enough levels of ATNC to account for the concentration of these compounds present in the beer after fermentation. These findings suggest that the presence of detectable levels of ATNC in some beers is a result of N-nitrosation reactions occurring in the fermenting wort with the nitrosating species derived from reduction of nitrate, due probably to the presence of microbial species with nitrate reductase activity.
 ...
PMID:An investigation of apparent total N-nitroso compounds in beer. 367 72

Gel chromatography experiments over a wide range of protein concentrations showed that Chlorella nitrate reductase is a nonassociating protein with a Stokes radius of 81 A. Sedimentation equilibrium of nitrate reductase in H2O-D2O solvents yielded a partial specific volume of 0.800 +/- 0.014 (n = 12) and a Mr = 360,000 +/- 25,000. No lipid was found associated with nitrate reductase. Cross-linking with the bifunctional reagent, dimethyl suberimidate, and subsequent separation of products by sodium dodecyl sulfate-polyacrylamide gel electrophoresis yielded four protein-staining bands in which the molecular weights of the cross-linked products were integral multiples of the monomeric molecular weight (90,000). Extensive cross-linking of the enzyme resulted in one principal protein-staining band of 360,000, corresponding to a tetramer. The cross-linked tetramer of nitrate reductase appeared to have identical physical properties as the native enzyme. The cross-linking pattern produced by reaction with dimethyl suberimidate suggested that nitrate reductase is an isologous tetramer which has at least two different types of bonding domains. Gel filtration, sedimentation equilibrium, and density gradient experiments at very low enzyme concentrations indicated that nitrate reductase dissociates to a species with a Stokes radius of 54 A, s20.w of 7.1, and Mr = approximately 200,000 at these low enzyme concentrations. No change in specific activity of the enzyme was observed over this concentration range. Treatment of nitrate reductase with trypsin or with cyanogen bromide yielded the number of peptides expected for identical subunits. From these results, it is concluded that Chlorella nitrate reductase is a homotetramer with dihedral symmetry ("dimer of dimers").
 ...
PMID:Quaternary structure of assimilatory NADH:nitrate reductase from Chlorella. 720 4

Assimilatory nitrate reductase has been purified with 55% recovery from a Neurospora crassa nmr-1 nit-6 mutant, using a modification of a published procedure. It possesses one heme per 240 000 g, and subunits of mol. wt. 68 000. Upon digestion with chymotrypsin, a heme-binding domain was isolated by gel filtration; its visible spectrum was highly similar to that of cytochrome b(5). On SDS gels, the fraction showed two heme-containing bands of 10 000 and 12 5000 daltons; their amino acid composition was not very different, suggesting that they originated from the same region of the polypeptide chain. After S-carboxymethylation, the mixture of bands was submitted to cyanogen bromide cleavage, and the fragments were separated by h.p.l.c. The two largest fragments yielded an identical sequence upon automated degradation. This sequence (39 residues with some gaps) could be easily aligned with that of cytochrome b(5) starting close to the N terminus. These results are discussed in terms of the possible quaternary structure of N. crassa nitrate reductase, whose heme-binding domain proves to be another member of the family of b(5)-like cytochromes.
 ...
PMID:On the presence of a heme-binding domain homologous to cytochrome b(5) in Neurospora crassa assimilatory nitrate reductase. 1645 80

To investigate the effects of 2,3,5,4'-tetrahydroxystilbene-2-O-beta-D-glucoside (THSG), a compound extracted from the root of Polygonum multiflorum Thunb, on lipoprotein (LDL and VLDL) oxidation, proliferation and nitric oxide (NO) content of coronary arterial smooth cells (CASMCs) induced by LDL, VLDL, ox-LDL and ox-VLDL. The oxidation level of lipoprotein was determined by thiobabituric acid (TBA) method and agarose gel electrophoresis. The proliferative degree was determined by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) method. The NO content was assayed by nitrate reductase method. (1)THSG (0.1 - 100 mumol L(- 1)) could dose-dependently prevent lipoprotein from oxidation induced by Cu(2 + ) and CASMCs. (2)THSG (0.1 - 100 micromol L(- 1)) inhibited porcine CASMCs proliferation elicited by LDL, VLDL, ox-LDL and ox-VLDL. (3)THSG (0.1 - 100 micromol L(- 1)) counterpoised the decrease of NO content in CASMCs evoked by LDL, VLDL, ox-LDL and ox-VLDL. As compared with control, it was found that the threshold concentration of THSG, which significantly exerted the actions mentioned above, were at the concentration of 1 micromol.L(- 1) (P < 0.01). In conclusion, THSG possesses the antagonistic effects on oxidation of lipoprotein, proliferation and decrease of NO content of CASMCs, which partially explain the mechanism of anti-atherosclerosis of Polygonum multiflorum Thunb.
 ...
PMID:Effect of 2,3,5,4'-tetrahydroxystilbene-2-O-beta-D-glucoside on lipoprotein oxidation and proliferation of coronary arterial smooth cells. 1770 57

This study investigated the effects of the peroxisome proliferator-activated receptor-gamma agonist rosiglitazone (RGZ) on cardiac fibroblast proliferation, nitric oxide content and connective tissue growth factor (CTGF) expression following incubation with advanced glycation end-products (AGEs). Cultured neonatal rat cardiac fibroblasts were incubated with various concentrations of AGEs for 48 h. Cells were also incubated with 200 mg/l AGEs plus various concentrations of RGZ. Cardiac fibroblast proliferation and cell cycle status were detected using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry. Western blotting was used to measure the expression of CTGF and nitric oxide content was evaluated using a nitrate reductase assay. AGEs significantly accelerated proliferation, increased CTGF expression and decreased nitric oxide production in cardiac fibroblasts. These effects of AGEs were inhibited by RGZ in a dose-dependent manner. Treatment with RGZ could be a valuable therapeutic approach in diabetic patients with myocardial fibrosis.
 ...
PMID:Effect of rosiglitazone on cardiac fibroblast proliferation, nitric oxide production and connective tissue growth factor expression induced by advanced glycation end-products. 1838 Sep 44