Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.9.3.1 (cytochrome oxidase)
 8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Plasma membranes were isolated and separated from thylakoid membranes by discontinuous sucrose density gradient centrifugation of crude membranes prepared by French pressure cell extrusion of lysozyme-treated Anacystis nidulans. Two distinct populations of chlorophyll-free plasma membrane vesicles were obtained exhibiting buoyant densities of 1.087 and 1.100 g/cm3 as opposed to a uniform density of 1.192 g/cm3 for thylakoid membranes. Plasma and thylakoid membranes were characteristically different also with respect to fatty acid and protein composition, cytochrome oxidase activity, and pigment content as analyzed by spectrophotometry, spectrofluorimetry, and high performance liquid chromatography. Apart from carotenoids, chlorophyll a was the only major photosynthetic pigment detected in thylakoid membranes while plasma membranes contained virtually no chlorophyll a but (besides large amounts of carotenoids) protochlorophyllide a and chlorophyllide a as revealed by solvent partition (between n-hexane and acetone or methanol), room and low temperature fluorescence emission and excitation spectra, and analytical separation and identification by high performance liquid chromatography and comparison with authentic standards. The protochlorophyllide in the plasma membrane could be transformed into chlorophyllide in the dark in vitro by incubating the membrane preparation with NADPH; NADP+ effected the reverse transition.
 ...
PMID:Chlorophyll precursors in the plasma membrane of a cyanobacterium, Anacystis nidulans. Characterization of protochlorophyllide and chlorophyllide by spectrophotometry, spectrofluorimetry, solvent partition, and high performance liquid chromatography. 250 Dec 98

Cytochrome components which participate in the oxidation of nitrite in Nitrobacter winogradskyi have been highly purified and their properties studied in detail. Cytochrome a1c1 is an iron-sulphur molybdoenzyme which has haems a and c and acts as a nitrite-cytochrome c oxidoreductase. Cytochrome c-550 is homologous to eukaryotic cytochrome c and acts as the electron mediator between cytochrome a1c1 and aa3-type cytochrome c oxidase. The oxidase is composed of two kinds of subunits, has two molecules of haem a and two atoms of copper in the molecule, and oxidizes actively eukaryotic ferrocytochrome c as well as its own ferrocytochrome c-550. Further, a flavoenzyme has been obtained which has transhydrogenase activity and catalyses reduction of NADP+ with benzylviologen radical. This enzyme may be responsible for production of NADPH in N. winogradskyi. The electron transfer against redox potential from NO2- to cytochrome c could be pushed through prompt removal by cytochrome aa3 of H+ formed by the dehydrogenation of NO2- + H2O. As cytochrome c in anaerobically kept cell-free extracts is rapidly reduced on addition of NO2-, a membrane potential does not seem necessary for the reduction of cytochrome c by cytochrome a1c1 with NO2- in vivo.
 ...
PMID:The nitrite oxidizing system of Nitrobacter winogradskyi. 285 89

Enzyme histochemical methods were performed on sporozoite infected liver tissue of rats in order to gain insight into the nutrition and metabolism of exoerythrocytic forms of Plasmodium berghei. The following enzymes were demonstrated in the hepatocytic stages of the parasites, obtained 41 and 48 h after inoculation of sporozoites: acid phosphatase, cytochrome oxidase, NADH-tetrazolium reductase, succinate dehydrogenase, NAD+ and NADP+ dependent isocitrate dehydrogenase, NADP+-dependent malate dehydrogenase, lactate dehydrogenases, 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenases and alpha-glycerol-phosphate dehydrogenase. The results suggest that a conventional Embden-Meyerhoff pathway, pentose phosphate pathway and Krebs' citric acid cycle may in part be present in these exoerythrocytic parasites. Alkaline phosphatase, nucleoside polyphosphatase, 5' nucleotidase, glucose-6-phosphatase, alpha-glucan phosphorylase, NAD+ dependent malate dehydrogenase, amino-peptidase M and non-specific esterases were not detected by our techniques in the parasite. The enzyme distribution of this intrahepatocytic malaria parasite revealed by histochemistry is compared with the enzyme distribution in the other phases of the parasite's life cycle.
 ...
PMID:Histochemical observations on the exoerythrocytic malaria parasite Plasmodium berghei in rat liver. 608 94

The effect of potassium cyanide on p-nitroanisole O-demethylation in perfused rat livers has been examined. Cyanide (2 mM), an inhibitor of cytochrome oxidase, diminished p-nitroanisole O-demethylation by 50-75% in perfused livers from normal and phenobarbital-treated rats, but had much less effect on hepatic microsomal p-nitroanisole O-demethylation. The inhibition was also observed in livers where the activity of the pentose phosphate shunt was abolished by pretreatment with 6-aminonicotinamide. Cyanide infusion decreased hepatic ATP/ADP ratios and cellular concentrations of glutamate, alpha-ketoglutarate, and isocitrate, but caused an increase in the NADP+/NADPH ratio. Rates of NADPH generation via the pentose phosphate shunt were unchanged by cyanide, and hepatic concentrations of glucose 6-phosphate were markedly increased by cyanide. Thus, inhibition of p-nitroanisole metabolism could not be explained solely by a direct interaction of cyanide with mixed-function oxidases or diminished NADPH generation via the pentose cycle. These data indicate that cyanide inhibits mixed-function oxidation in intact cells by diminishing the generation of NADPH from sources other than the pentose cycle. Further, these data are consistent with the hypothesis that some NADPH for mixed-function oxidation arises from cyanide-sensitive mitochondrial sources.
 ...
PMID:Inhibition of p-nitroanisole O-demethylation in perfused rat liver by potassium cyanide. 631 Nov 7

ATP-dependent calcium sequestration was previously localized in vesicles of mitotic apparatus isolated from sea urchins. We now demonstrate that the mitotic apparatus contains an ATP-regenerative system characterized as creatine kinase (EC 2.7.3.2). Mitotic apparatus isolated with vesicles intact converted ADP to ATP if phosphocreatine was present. Omission of ADP or phosphocreatine gave negligible ATP. When mitotic apparatus were washed with detergent-containing buffer to remove vesicles, their ability to produce ATP from ADP and phosphocreatine was reduced. Assays of creatine kinase activity using NADP+:glucose-6-phosphate dehydrogenase indicated that 70% of the creatine kinase activity was extractable with 0.5% Triton X-100. The insoluble residue containing the skeleton of the mitotic apparatus had the rest of the activity. Experiments with a luciferin/luciferase assay showed that Triton removed above 82% of the activity. Preparations of intact mitotic apparatus were free of cytochrome c oxidase (EC 1.9.3.1) activity and therefore free of mitochondria. About 10(8) mitotic apparatus (total volume about 1 liter) could produce 17 mmol of ATP/min when substrates were not limiting. The creatine kinase enzyme activity described herein and the previously described membrane vesicular calcium sequestration system are nonmitochondrial, integral constituents of the sea urchin mitotic apparatus.
 ...
PMID:Identification of nonmitochondrial creatine kinase enzymatic activity in isolated sea urchin mitotic apparatus. 631 91

The glbN gene of Nostoc commune UTEX 584 is juxtaposed to nifU and nifH, and it encodes a 12-kDa monomeric hemoglobin that binds oxygen with high affinity. In N. commune UTEX 584, maximum accumulation of GlbN occurred in both the heterocysts and vegetative cells of nitrogen-fixing cultures when the rate of oxygen evolution was repressed to less than 25 micromol of O2 mg of chlorophyll a(-1) h(-1). Accumulation of GlbN coincided with maximum synthesis of NifH and ferredoxin NADP+ oxidoreductase (PetH or FNR). A total of 41 strains of cyanobacteria, including 40 nitrogen fixers and representing 16 genera within all five sections of the cyanobacteria were screened for the presence of glbN or GlbN. glbN was present in five Nostoc strains in a single copy. Genomic DNAs from 11 other Nostoc and Anabaena strains, including Anabaena sp. strain PCC 7120, provided no hybridization signals with a glbN probe. A constitutively expressed, 18-kDa protein which cross-reacted strongly with GlbN antibodies was detected in four Anabaena and Nostoc strains and in Trichodesmium thiebautii. The nifU-nifH intergenic region of Nostoc sp. strain MUN 8820 was sequenced (1,229 bp) and was approximately 95% identical to the equivalent region in N. commune UTEX 584. Each strand of the DNA from the nifU-nifH intergenic regions of both strains has the potential to fold into secondary structures in which more than 50% of the bases are internally paired. Mobility shift assays confirmed that NtcA (BifA) bound a site in the nifU-glbN intergenic region of N. commune UTEX 584 approximately 100 bases upstream from the translation initiation site of glbN. This site showed extensive sequence similarity with the promoter region of glnA from Synechococcus sp. strain PCC 7942. In vivo, GlbN had a specific and prominent subcellular location around the periphery of the cytosolic face of the cell membrane, and the protein was found solely in the soluble fraction of cell extracts. Our hypothesis is that GlbN scavenges oxygen for and is a component of a membrane-associated microaerobically induced terminal cytochrome oxidase.
 ...
PMID:GlbN (cyanoglobin) is a peripheral membrane protein that is restricted to certain Nostoc spp. 893 16

Electron transfer rates to P700+ have been determined in wild-type and three interposon mutants (psaE-, ndhF-, and psaE- ndhF-) of Synechococcus sp. PCC 7002. All three mutants grew significantly more slowly than wild type at low light intensities, and each failed to grow photoheterotrophically in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and a metabolizable carbon source. The kinetics of P700+ reduction were similar in the wild-type and mutant whole cells in the absence of DCMU. In the presence of DCMU, the P700+ reduction rate in the psaE mutant was significantly slower than in the wild type. In the presence of DCMU and potassium cyanide, added to inhibit the outflow of electrons through cytochrome oxidase, P700+ reduction rates increased for both the psaE- and ndhF- strains. The reduction rates for these two mutants were nonetheless slower than that observed for the wild-type strain. The further addition of methyl viologen caused the rate of P700+ reduction in the wild type to become as slow as that for the psaE mutant in the absence of methyl viologen. Given the ability of methyl viologen to intercept electrons from the acceptor side of photosystem I, this response reveals a lesion in cyclic electron flow in the psaE mutant. In the presence of DCMU, the rate of P700+ reduction in the psaE ndhF double mutant was very slow and nearly identical with that for the wild-type strain in the presence of 2,4-dibromo-3-methyl-6-isopropyl-p-benzoquinone, a condition under which physiological electron donation to P700+ should be completely inhibited. These results suggest that NdhF- and PsaE-dependent electron donation to P700+ occurs only via plastoquinone and/or cytochrome b6/f and indicate that there are three major electron sources for P700+ reduction in this cyanobacterium. We conclude that, although PsaE is not required for linear electron flow to NADP+, it is an essential component in the cyclic electron transport pathway around photosystem I.
 ...
PMID:PsaE Is Required for in Vivo Cyclic Electron Flow around Photosystem I in the Cyanobacterium Synechococcus sp. PCC 7002. 1223 24