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PubMed1995

A light-induced protease from barley plastids degrades NADPH:protochlorophyllide oxidoreductase complexed with chlorophyllide.

The NADPH:protochlorophyllide oxidoreductase precursor protein (pPorA) of barley (Hordeum vulgare L. cv. Carina), synthesized from a full-length cDNA clone by coupling in vitro transcription and translation, is a catalytically active protein. It converts protochlorophyllide to chlorophyllide in a light- and NADPH-dependent manner. At least the pigment product of catalysis remains tightly bound to the precursor protein. The chlorophyllide-pPorA complex differs markedly from the protochlorophyllide-pPorA complex with respect to sensitivity to attack by a light-induced, nucleus-encoded, and energy-dependent protease activity of barley plastids. The pPorA-chlorophyllide complex is rapidly degraded, in contrast to pPorA-protochlorophyllide complexes containing or lacking NADPH, which are both resistant to protease treatment. Unexpectedly, pPorA devoid of its substrates or products was less sensitive to proteolysis than the pPorA-chlorophyllide complex, suggesting that both substrate binding and product formation during catalysis had caused differential changes in protein conformation.

Adenosine Triphosphate↗
PubMed1995

Sulfhydryl-disulfide modulation and the role of disulfide oxidoreductases in regulation of the catalytic activity of nitric oxide synthase in pulmonary artery endothelial cells.

The role of sulfhydryl groups (SH) and disulfide bonds as well as disulfide oxidoreductases in regulation of the catalytic activity of the membrane-bound constitutive isoform of nitric oxide (NO) synthase from porcine pulmonary artery endothelial cells (PAEC) was examined. Treatment of intact PAEC or a total membrane preparation isolated from PAEC with the SH alkylating agent N-ethylmaleimide (NEM) (10 to 50 microM) or with the intramolecular disulfide-forming agent diamide (20 to 100 microM) resulted in the reduction of NO synthase activity in a dose-dependent fashion. Similar loss of enzyme activity was observed when purified NO synthase from the membrane fraction of PAEC was incubated in the presence of NEM. The loss of membrane protein SH content from NEM- and diamide-treated preparations was associated with loss of NO synthase activity. In contrast, when intact PAEC or isolated total membranes derived from PAEC were treated with increasing concentrations (1 to 5 mM) of the disulfide-reducing agent dithiothreitol (DTT), but not oxidized DTT, NO synthase activity was increased by 20 to 85%. DTT reduction of native disulfides from NEM-treated preparations or of disulfides formed after diamide treatment of membranes reversed the inhibition of NO synthase activity. Similarly, enzymatic reduction by thioredoxin/thioredoxin reductase, but not by glutaredoxin, reversed the inhibition of membrane fraction and purified NO synthase isolated from diamide-treated cells. This enzyme-catalyzed disulfide reduction was > 1,000-fold more efficient than the DTT-induced reduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Oxidoreductases↗
PubMed2004

Carbonyl reduction of naltrexone and dolasetron by oxidoreductases isolated from human liver cytosol.

The opioid receptor antagonist naltrexone and the antiemetic 5-HT(3) receptor antagonist dolasetron are ketonic drugs that are efficiently reduced to their corresponding alcohols in-vivo. These experiments aimed at characterizing the role in these reactions of individual oxidoreductases present in human liver cytosol. Aldo-keto reductases (AKRs) and carbonyl reductase (CR, EC 1.1.1.184) purified from human liver cytosol were incubated with varying substrate concentrations and 6beta-naltrexol or reduced dolasetron were analysed by HPLC. AKR1C1, AKR1C2, and AKR1C4 were able to reduce both substrates. On the basis of k(cat)/K(m) values, AKR1C4 was nearly 1000-fold more efficient in reducing naltrexone than was AKR1C1, while AKR1C2 was of intermediate efficiency. Substrate inhibition was observed on incubating AKR1C2 or AKR1C4 with naltrexone. In contrast, dolasetron was also a substrate of CR. AKR1C1 and AKR1C4 were the most efficient enzymes in producing reduced dolasetron. We concluded that the efficient reduction of naltrexone by AKR1C4 probably causes the high 6beta-naltrexol/naltrexone ratio in man. The rapid disappearance from human plasma of dolasetron given intravenously and its virtual absence after oral dosage are explained by its liability to reduction by several enzymes, including CR which shows widespread expression in human tissues.

Alcohol Oxidoreductases↗
PubMed2000

NADPH:Protochlorophyllide oxidoreductase uses the general import route into chloroplasts.

Chloroplast differentiation in angiosperm plants depends on the light-dependent conversion of protochlorophyllide to chlorophyllide by NADPH:protochlorophyllide oxidoreductase (PORA; EC 1.6.99.1), a nuclearly encoded protein. The protein import of the precursor form of PORA into plastids was shown previously to strictly depend on the presence of its substrate protochlorophyllide. PORA seemed to follow a novel, posttranslationally regulated import route. Here we demonstrate that the precursor of PORA from barley is imported into isolated barley plastids independently of protochlorophyllide. PORA as well as PORB import is competed for by the precursor of the small subunit of Rubisco. The data demonstrate that the PORA precursor uses the general import pathway into plastids. Furthermore, en route into chloroplasts the pea POR precursor can be cross-linked to the protein import channel in the outer envelope Toc75 from pea.

Aminolevulinic Acid↗
PubMed1992

Microbial metabolism of quinoline and related compounds. XV. Quinoline-4-carboxylic acid oxidoreductase from Agrobacterium spec.1B: a molybdenum-containing enzyme.

The quinoline-4-carboxylic acid oxidoreductase from Agrobacterium spec.1B was purified 84-fold to apparent homogeneity with 15% recovery, using ammonium sulphate precipitation, heat precipitation, hydrophobic interaction, anion exchange- and gel chromatography. The molecular mass of the native enzyme was estimated to be 320 kDa by gel filtration. SDS-polyacrylamide gel electrophoresis of the enzyme revealed three protein bands corresponding to 85, 35 and 21 kDa. Per molecule the enzyme contains 8 atoms of iron, 8 atoms of acid-labile sulphur, 2 atoms of molybdenum, 2 molecules of FAD and as molybdenum cofactor, molybdopterin cytosine dinucleotide. Besides quinoline-4-carboxylic acid the enzyme also catalysed the conversion of quinoline, 4-chloroquinoline and 4-methylquinoline to the corresponding 2-oxo-1,2-dihydroderivatives. Cyanide, methanol, 4-chloromercuribenzoate and acriflavin were effective inhibitors.

Chromatography, Gel↗
PubMed1999

The oxidoreductase, biliverdin reductase, is induced in human renal carcinoma--pH and cofactor-specific increase in activity.

PURPOSE: Biliverdin reductase is an oxidoreductase unique among all enzymes characterized to date in having dual pH/dual cofactor requirement - NADH and NADPH at 6.7 and 8.7, respectively. The protein shows extensive microheterogeneity that is caused by post-translational modification. The reductase converts the heme degradation product, biliverdin, to bilirubin. Bilirubin has been shown to inhibit responses of human lymphocytes, including phytohemagglutinin-induced proliferation, interleukin-2 production, and antibody dependent and independent cell mediated cytotoxicity. In addition to acting as an antioxidant, it inhibits protein phosphorylation and activity of enzymes such as protein kinase C and NADPH oxidase. This research was to evaluate whether renal cell carcinoma differs from normal tissue in regard to the expression and activity of the reductase. MATERIALS AND METHODS: Kidney tissue with or without visible renal carcinoma and normal kidney tissue from a brain dead patient were frozen at -80C shortly after removal. Ten microm. tissue sections were used for immunostaining of biliverdin reductase, pooled isolated tumors and surrounding tissue that did not contain visible tumor were used for Northern blot analysis of mRNA and Western blot analysis of protein. Enzyme activity was also measured in these preparations at pH 6.7 with NADH, and at pH 8.7 with NADPH. Ten additional formalin fixed specimens of renal cell carcinoma were also used for immunostaining. RESULTS: There was a striking increase in the reductase protein levels, as visualized by immunostaining in tumor tissue cells. The increase was also evident by Western blotting, and involved in increased transcription of biliverdin reductase as suggested by Northern blot analysis. The protein would also be detected in the infiltrating monocytes, macrophages, T cells and neutrophils as well as in circulating lymphocytes. The enzyme activity was nearly doubled in the tumor tissue, but selectively with NADH as the cofactor. CONCLUSION: Increases in biliverdin reductase expression and activity only with NADH is found in renal cell carcinoma. The net effects of this change are uncertain at present but several pathways, which could be affected by the reductase, may alter local physiology. Biliverdin reductase as a zinc metalloprotein may directly interact with other regulatory proteins, generation of increased bilirubin may alter immune function and increased enzyme activity may deplete NADH with contrasting consequence of blocking free radical formation and depleting cellular ATP. To the benefit of the host, the latter could culminate in tumor cell death.

Carcinoma, Renal Cell↗
PubMedDate not supplied

[Effect of ammonium on certain oxidoreductases of wine yeasts].

The effect of ammonium ions on the activity of alcohol:NAD-, L-malate:NAD-, L-glutamate:NADP-oxidoreductases was studied in wine yeast during fermentation of wine wort containing 18% of sugar, and also after the biomass cultivated in the conditions of nitrogen deficiency had been transferred to media with various amounts of nitrogen and carbohydrates. Ammonium stimulated the activity of all these enzymes during fermentation and their activity in the biomass transferred to a medium with a low content of nutrient component; its effect was less pronounced on a complete medium.

Alcohol Oxidoreductases↗
PubMed1992

NADPH: protochlorophyllide oxidoreductases in white pine (Pinus strobus) and loblolly pine (P. taeda). Evidence for light and developmental regulation of expression and conservation in gene organization and protein structure between angiosperms and gymnosperms.

NADPH: protochlorophyllide oxidoreductase (pchlide reductase, EC 1.6.99.1) catalyzes the light-dependent reduction of protochlorophyllide in higher plants. Cloned cDNAs encoding two distinct pchlide reductases were isolated from a lambda gt11 library constructed from poly(A)+ RNA prepared from the cotyledons of dark-grown white pine (Pinus strobus) seedlings and a nuclear gene (lpcr) analogous to one of these cDNAs has been characterized from loblolly pine (P. taeda). The pine gene encodes an approximately 43 kDa precursor polypeptide consisting of a 334-amino acid mature protein and a 66-amino acid transit peptide. The deduced primary structures for the pine proteins are highly homologous to those reported from monocots and dicots. The coding portion of the pine lpcr gene is interrupted by four introns. The placement of these introns within the pine lpcr gene is identical to that observed in pea (Pisum sativum), suggesting conservation in gene organization between dicot and gymnosperm species. Western blot analysis using polyclonal antiserum against oat pchlide reductase detected in extracts of dark-grown pine cotyledons a single immunoreactive protein, which declined in abundance during a 48 h period of illumination with white light. Cotyledons of dark-grown seedlings were also found to accumulate high levels of pchlide reductase mRNA; however, little or no change in the steady-state levels of mRNA encoding pchlide reductase was observed in these tissues following illumination. Stem tissue of dark-grown seedlings did not contain significant levels of pchlide reductase mRNA, whereas stems of light-grown plants of the same age accumulated substantial amounts of the message. These results suggest that light and the developmental age of the tissue affect regulation of lpcr expression in pine.

Amino Acid Sequence↗
PubMed1991

An investigation on the quinoprotein nature of some fungal and plant oxidoreductases.

The presence of pyrroloquinoline quinone (PQQ) as the organic cofactor of Dactylium dendroides galactose oxidase and lentil (Lens culinaris) seedling amine oxidase, purported PQQ-containing oxidoreductases (Van der Meer, R. A., Jongejan, J. A., and Duine, J. A. (1989) J. Biol. Chem. 264, 7792-7794; Citro, G., Verdina, A., Galati, R., Floris, G., Sabatini, S., and Finazzi-Argo', A. (1989) FEBS Lett. 247, 201-204), was reinvestigated using the nitro blue tetrazolium redoxcycling method (Paz, M. A., Gallop, P. M., Torrelio, B. M., and Flückiger, R. (1988) Biochem. Biophys. Res. Commun. 154, 1330-1337; Paz, M. A., Flückiger, R., Boak, A., Kagan, H. M., and Gallop, P. M. (1991) J. Biol. Chem. 266, 689-692) and the enzyme-linked immunosorbent assay with polyclonal antibodies against PQQ. The possible quinoprotein nature of the laccases from Polyporus versicolor and Rhus vernicifera was also investigated because of the similarities in spectroscopic and kinetic features of these enzymes and the laccase from Phlebia radiata, reported to be a PQQ protein (Karhunen, E., Niku-Paavola, M.-L., Viikari, L., Haltia, T., Van der Meer, R. A., and Duine, J. A. (1990) FEBS Lett. 267, 6-8). The presence of a quinonoid cofactor in lentil seedling amine oxidase is confirmed, whereas galactose oxidase and both laccases do not display any quinoprotein nature.

Amine Oxidase (Copper-Containing)↗
PubMed1980

Reconstitution of a formate-NADP+ oxidoreductase from formate dehydrogenase and a 5-deazaflavin-linked NADP+ reductase isolated from Methanococcus vannielii.

The formate-dependent reduction of NADP+ by extracts of Methanococcus vannielii is catalyzed by a coupled system consisting of formate dehydrogenase, a 5-deazaflavin cofactor, and 5-deazaflavin-dependent NADP+ reductase. All three components were purified from crude extracts of M. vannielii. Recombination of these components reconstituted the formate-NADP+ oxidoreductase system. The formate dehydrogenase also can utilize FAD, FMN, and a number of artificial dyes as electron acceptors, but these do not replace the 5-deazaflavin cofactor in the coupled enzyme system. The reduced form of 5-deazaflavin binds readily to the NADP+ reductase apoprotein and is not dissociated by ammonium sulfate treatment at neutral pH under anaerobic conditions. This electron transfer cofactor from M. vannielii is identical in many of its properties to the 5-deazaflavin isolated from other methane-producing bacteria.

Aldehyde Oxidoreductases↗
PubMed1998

Increased expression of NADH-ubiquinone oxidoreductase chain 2 (ND2) in preimplantation rabbit embryos cultured with 20% oxygen concentration.

In vitro culture of mammalian preimplantation embryos is associated with various developmental disorders such as retardation in development and cell damage. The molecular mechanisms underlying these processes are poorly understood. One of the possible reasons may be the unphysiologically high oxygen concentration used for culture. Four-day-old rabbit blastocysts were cultured with 5% O2 (physiologic oxygen concentration) or 20% O2 (usually used for in vitro culture) for 4 hr. Differences in gene expression were analysed by differential display reverse-transcriptase polymerase chain reaction (DD RT-PCR). Thirty-two differentially expressed RNA bands were found. Two of them revealed a high sequence homology to the equine NADH-ubiquinone oxidoreductase chain 2 (ND2), a subunit of complex I of the respiratory chain. mRNA expression of ND2 was increased in blastocysts cultured with the higher oxygen concentration. Increased expression of ND2 was confirmed by semiquantitative and semiquantitative competitive RT-PCR.

Animals↗
PubMed2004

Plasma membrane NADH-oxidoreductase in cells carrying mitochondrial DNA G11778A mutation and in cells devoid of mitochondrial DNA (rho0).

The mammalian plasma membrane (PM) NADH-oxidoreductase (PMOR) system is a multi-enzyme complex located in the plasma membrane of all eukaryotic cells, harboring at least two distinct activities, the plasma membrane NADH-ferricyanide reductase and the NADH-oxidase. To assess the behaviour of the two activities of the PMOR system, we measured the NADH-ferricyanide reductase and NADH-oxidase activities in fibroblast cell lines derived from patients carrying a mitochondrial DNA (mtDNA) G11778A mutation. We also measured the two activities in other cell lines, the HL-60 and HeLa (S3) lines, as well as in rho0 cells (cells devoid of mtDNA) generated from those lines and the fibroblast cells. These rho0 cells consequently lack oxidative phosphorylation and rely on anaerobic glycolysis for their ATP need. We have proposed that in rho0 cells, at least in part, up-regulation of the PMOR is a necessity to maintain the NAD+/NADH ratio, and a pre-requisite for cell growth and viability. We show here that the PM NADH-ferricyanide reductase activity was up-regulated in HL-AV2 (HL-60 rho0) cell lines, but not in the other rho0 and mtDNA mutant lines. The plasma membrane NADH oxidase activity was found to be up-regulated in both HL-AV2 and HeLa rho0 cell lines, but not significantly in the fibroblast rho0 and G11778A lines.

Cell Membrane↗
PubMed1977

Amperometric assay of coenzyme-dependent oxidoreductase enzymes in a flow-through cell.

We have demonstrated that a simple electrochemical cell can serve as a detector of NADH concentration in a flow system thereby providing an assay technique for NADH dependent enzymes. When this is applied to NADH produced by enzymatic reaction, then a reproducible measure of enzyme activity is obtained. This method of enzyme activity assay is applicable to a number of oxidoreductase enzymes which employ NAD+ or NADP+ as coenzymes to achieve substrate modification. The presence of electroactive species in samples of human serum has proved a serious problem in the electrochemical analysis of serum activity. These species produce a large background anode current at the anode voltage appropriate for NADH oxidation. The presence of this high current limits the usefulness of amplification of the current output to detect small changes in NADH concentration.

Alcohol Oxidoreductases↗
PubMed1990

Electrophoresis at elevated hydrostatic pressure of the multiheme hydroxylamine oxidoreductase.

The behavior of the multiheme protein hydroxylamine oxidoreductase (HAO) in polyacrylamide gel electrophoresis was studied at hydrostatic pressures up to 3 kbar at 25 degrees C. Due to the limited working volume of the high pressure vessel, the electrophoresis cells were miniaturized. A microcell which accommodates 6 capillary gel tubes is described. Between 1 bar and 1.5 kbar the enzyme did not undergo structural changes detectable in the gel system. At approximately 2 kbar the active form of the enzyme was partially dissociated. At higher pressures, the enzyme was converted to forms which were irreversibly inactive and had a higher apparent molecular mass, suggesting aggregation or denaturation.

Atmospheric Pressure↗
PubMed1992

cDNA sequence of three cysteine-rich clusters in the iron-sulfur subunit of complex II (succinate-ubiquinone oxidoreductase) from Caenorhabditis elegans determined by automated DNA sequencer.

Homology probing by using mixed primers for polymerase chain reaction (PCR) and a subsequent sequence analysis by automated DNA sequencer were applied to determine a partial cDNA sequence of the iron-sulfur subunit of complex II (succinate-ubiquinone oxidoreductase). Complex II is a membrane-bound flavoenzyme, which catalyzes the oxidation of succinate to fumarate in the tricarboxylic acid cycle, and it is a component of the mitochondrial and bacterial respiratory chains. In this study, the partial amino acid sequence of iron-sulfur subunits in Caenorhabditis elegans mitochondria was deduced from the DNA sequence obtained from cDNA-PCR. Mixed oligonucleotide primers corresponding to two conserved regions which appear to be the binding site for the prosthetic group were used. The product of PCR was cloned into plasmid vector pUC 119 and the sequence was determined from double strand plasmid DNA by the dideoxy method using of one-dye, four-lane type the automated DNA sequencer (DSQ-1, Shimadzu). The PCR product contained 483 nucleotides and its deduced amino acid sequence was highly homologous with that in human liver (68.9%) and that of Escherichia coli sdh B product (50.3%). As expected, striking sequence conservation was found around the three cysteine-rich clusters which have been thought to comprise the iron-sulfur centers of the enzyme.

Amino Acid Sequence↗
PubMed1980

[Steroid transforming enzymes in microorganisms. XIII. Relationship between steroid structure and induction of 4-ene-3-oxosteroid: (acceptor)-1-ene-oxidoreductase in Nocardia opaca].

The induction of the 4-ene-3-oxosteroid: (acceptor)-1-ene-oxidoreductase in Nocardia opaca has been shown to be dependent on both hydrophilic and hydrophobic structural features of the steroid molecule, i.g. the nature of the oxygen function in positions 11 and 20 and the presence of the methyl group in position 10 influence the induction of the enzyme drastically. In this connection the metabolism of the steroid inductors being degradated during the induction process has been considered.

Enzyme Induction↗
PubMed1979

[Steroid-transforming enzymes from microorganisms. IX. Affinity chromatographic preparation and studies of the apoenzyme from a 4-en-3-oxosteroid: (acceptor)-1-en-oxidoreductase from Nocardia opaca].

From the flavoenzyme, 4-en-3-oxosteroid: (acceptor)-1-en-oxidoreductase of Nocardia opaca, prosthetic group and apoenzyme were separated quantitatively by means of affinity chromatography in the presence of 2 M (NH4)2 at pH 3.0. Subsequently the apoenzyme was eluted from affinity matrix by 0.01 M phosphate buffer, pH 8.0, whereas under these conditions the intact enzyme could not be eluted. The whole enzyme activity applied could be restored by incubation of the eluted apoenzyme with FAD. The binding strength of the apoenzyme to the immobilized steroid ligand is highly decreased in comparison to the native enzyme and can be interpreted by the action of rest hydrophobicity. That indicates the essential character of FAD for both ligand binding and transformation.

Ammonium Sulfate↗
PubMed2001

Prenatal diagnosis of NADH:ubiquinone oxidoreductase deficiency.

NADH:ubiquinone oxidoreductase (complex I of the mitochondrial respiratory chain) deficiency is a severe disorder with an often early fatal outcome. Prenatal diagnosis for complex I defects currently relies mainly on biochemical assays of complex I in fetal tissues such as chorionic villi (CV), and is only in a minority of cases possible by means of mutational analysis of nuclear-encoded genes of complex I. We report on our experience to date with prenatal diagnosis in pregnancies at risk for complex I deficiency. We measured complex I activity in native CV and/or cultured CV in 23 pregnancies in 15 families. In accordance with the results of the investigations in CV, 15 children were born clinically unaffected. Two prenatally diagnosed unaffected fetuses and two prenatally diagnosed affected fetuses were lost prematurely with spontaneous or provoked abortions, respectively. Two affected children were born (prenatally found to be affected). In two pregnancies a discrepancy between native and cultured cells was found. We conclude that prenatal diagnosis for complex I deficiency can be reliably performed. Pitfalls were encountered in using cultured CV as a result of maternal cell contamination (MCC). Future research on pathogenic nuclear mutations underlying complex I deficiency will extend the possibilities for prenatal diagnosis at the molecular level.

Biopsy↗