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PubMed1982

Neurosecretory nerve cells of rat and fish brain are rich in thiol-protein disulphide oxidoreductase (TPO) immunoreactivity.

Thio-protein disulphide oxidoreductase (TPO) was demonstrated in rat and fish brain by use of the indirect peroxidase-antiperoxidase technique. TPO immunoreactivity was found to be widely distributed throughout rat CNS. Whereas most nerve cells possessed only weak immunoreactivity to the enzyme, the neurosecretory cells of Nuc. supraopticus and Nuc. paraventricularis were heavily laden with immune products. In fishes (rudd) the neurosecret-producing neurons of the Nuc. preopticus were the only locus being positive for TPO. From our findings we conclude that thiol-protein disulphide oxidoreductase might be involved into the process of neurophysin synthesis.

Animals↗
PubMed1993

Purification and characterization of electron-transfer flavoprotein: rhodoquinone oxidoreductase from anaerobic mitochondria of the adult parasitic nematode, Ascaris suum.

Electron-transfer flavoprotein:rhodoquinone oxidoreductase (ETF-RO) was purified to homogeneity from anaerobic mitochondria of the parasitic nematode, Ascaris suum. The enzyme has a subunit molecular mass of 64.5 kDa and is similar in many respects to the electron-transfer flavoprotein:ubiquinone oxidoreductase (ETF-UO) characterized in mammalian tissues. EPR spectroscopy of the purified enzyme revealed signals at g = 2.076, 1,936, and 1.883, arising from an iron-sulfur center, as well as signals attributable to a flavin semiquinone. Potentiometric titration on the enzyme with dithionite yielded an oxidation-reduction midpoint potential (Em) for the iron-sulfur center of +25 mV at pH 7.4. The reduction of flavin occurred in two distinct steps, with a flavin semiquinone radical detected as an intermediate. The Em values for the two steps in the complete reduction of flavin were +15 mV and -9 mV, respectively. Physiologically, the ascarid ETF-RO accepts electrons from a low potential quinone, rhodoquinone, and functions in a direction opposite to that of the ETF-UO. Incubations of A. suum submitochondrial particles with NADH, 2-methylcrotonyl-CoA, purified A. suum electron-transfer flavoprotein and 2-methyl branched-chain enoyl-CoA reductase resulted in significant 2-methylbutyryl-CoA formation, which was inhibited by both rotenone and antisera to the purified ETF-RO. Quinone extraction of the submitchondrial particles with dry pentane resulted in almost the complete loss of 2-MBCoA formation by the system. However, the reincorporation of rhodoquinone, but not ubiquinone restored over 50% of the NADH-dependent 2-MBCoA formation.

Amino Acid Sequence↗
PubMed1993

Characterization of a novel tungsten-containing formaldehyde ferredoxin oxidoreductase from the hyperthermophilic archaeon, Thermococcus litoralis. A role for tungsten in peptide catabolism.

Thermococcus litoralis is a strictly anaerobic archaeon (archaebacterium) that grows at temperatures up to 98 degrees C by fermenting peptides. Its growth is stimulated by tungsten, and a tungsten-containing iron-sulfur protein that has formaldehyde ferredoxin oxidoreductase (FOR) activity has been purified. FOR is a homotetramer with a subunit M(r) of 70,000. It contains approximately four irons, four acid-labile sulfides, and one tungsten atom per subunit. The tungsten appears to be present as a pterin cofactor, and the Fe/S seems to comprise an unusual [4Fe-4S] cluster that in the reduced state exists in a pH-independent S = 3/2 form and a pH-dependent S = 1/2 form. FOR catalyzed the oxidation of C1-C3 aldehydes with a temperature optimum > or = 90 degrees C and used T. litoralis ferredoxin as an electron acceptor. It did not oxidize aldehyde phosphates, utilize CoASH, or reduce NAD(P). The N-terminal sequence of FOR shows homology with the tungsto-iron-sulfur aldehyde ferredoxin oxidoreductase previously purified from the saccharolytic, hyperthermophilic archaeon Pyrococcus furiosus, in which it is proposed to function in a novel pyroglycolytic pathway (Mukund, S., and Adams, M. W. W. (1991) J. Biol. Chem. 266, 14208-14216). We show here that P. furiosus, which will also grow on peptides, albeit poorly, contains a second aldehyde-oxidizing enzyme analogous to FOR. Similarly, T. litoralis, which utilizes saccharides if limited for peptides, contains low concentrations of an enzyme analogous to AOR. It is proposed that formaldehyde (apparent Km, 62 mM) is not the true substrate for FOR; rather, the enzyme has an as yet unknown role in peptide fermentation in hyperthermophilic archaea.

Aldehyde Oxidoreductases↗
PubMed1996

Pyruvate: ferredoxin oxidoreductase from Entamoeba histolytica recognized by a monoclonal antibody.

A mouse monoclonal antibody, Eh208C2-2 MAb, raised against whole cell antigens of Entamoeba histolytica trophozoites of the pathogenic strain HM-1: IMSS and polyclonal antisera (PAb) against membrane antigens of E. histolytica trophozoites of strain HTH-56: MUTM were screened against a cDNA library of the pathogenic strain, SFL3. The monoconal antibody detected many phage plaques expressing an E. histolytica protein. The DNA sequence encoding the protein was approximately 55% identical, over 1,100bp, to Trichomonas vaginalis pyruvate: ferredoxin oxidoreductase (PFOR) and pyruvate: flavodoxin oxidoreductase from Klebsiella pneumoniae, Anabaena variabilis and Enterobacter agglomerans. Two of seven clones detected by mouse polyclonal antisera also encoded this protein. Two others encoded Entamoeba Hsp70, another encoded Entamoeba alkyl-hydroperoxide reductase and the remaining two were unidentified sequences. Entamoeba PFOR is an abundant, antigenic protein which may be a useful target for the development of protective host immune responses against invasive amebiasis.

Amino Acid Sequence↗
PubMed1977

Purification and characterization of a thiol:protein disulfide oxidoreductase from bovine liver.

A thiol:protein disulfide oxidoreductase which degrades insulin into its A and B chains has been purified to homogeneity from bovine liver. The initial extraction procedure used 1% Triton X-100, which increased the soluble insulin degrading activity 100 to 800% as a result of solubilizing a membrane-associated enzyme. The criteria for homogeneity of the isolated protein include sodium dodecyl sulfate and disc gel electrophoresis. Characterization of the homogeneous protein by sedimentation equilibrium centrifugation indicates that a single protein is present which has a mass of 60,000 daltons. A single amino-terminal end group and molecular weight estimation by sodium dodecyl sulfate gel electrophoresis indicated that the thiol:protein disulfide oxidoreductase consists of a single polypeptide chain. The pure enzyme was also examined by gel filtration chromatography and has an apparent molecular weight of 92,000. The amino acid composition and carbohydrate content were also determined. The carbohydrate analysis demonstrated the presence of D-mannose, D-galactose, 2-acetamido-2-deoxy-D-glucose, and N-acetylneuraminic acid which comprise a total of 12% by weight of the isolated protein.

Amino Acids↗
PubMedDate not supplied

[Participation of polyvalent metals in the evolution of oxidoreductases].

The study of the participation of metals in evolution of oxidation-reduction processes is subdivided into two periods. During the first of them, from 1897 to 1937, the significance of manganese, iron, titanium, molybdenum, vanadium and copper in most important processes of metabolism was discovered. The second period, from 1937 to 1977, was devoted to the study of the role of metals in individual representatives of oxidoreductases and their evolution during transition of organisms from anaerobiosis to aerobiosis. In this evolution of special importance were bimetallic enzymes, such as nitrogenase, some nitrate reductases and hydrogenases, carbon dioxide reductase, xanthine oxidase, cytochrome oxidase. Owing to their ability to accomplish conjugated oxidation-reduction reactions, these oxidoreductases were transitional to still more complicated polymetallic systems with whose participation the electron transfer chains in subcellular structures were formed.

Binding Sites↗
PubMed1996

[Control of buccal peroxidases by a bacterial NADH-hypothiocyanite oxidoreductase].

Oral peroxidases (myeloperoxidase, sialoperoxidase) catalyze thiocyanate peroxidation into hypothiocyanite which is bacteriostatic or bactericidal against numerous bacterial species. NADH-hypothiocyanite-oxidoreductase is thought to protect bacteria which can express it; up to now, this enzyme activity was never purified. The present study analyzes, on one hand, the susceptibility of periodontal bacteria against hypothiocyanite and, on the other hand, proposes a purification design for the NADH-hypothiocyanite-oxidoreductase from Streptococcus sanguis, a commensal micro-organism of dental surfaces. The data suggest the importance of the bacterial biofilm on dental surfaces for production of antiseptic oxidants and for the control of their toxicity.

Anti-Infective Agents, Local↗
PubMed1999

A study on cytochrome c oxidoreductase for bonding a tri-n-butylborane-initiated luting agent to dentin.

The purpose of this study was to investigate the effectiveness of cytochrome c, an oxidoreductase, in terms of initiation of polymerization in dentin bonding. The efficacy of experimental dentin primers was evaluated via the bonding of a luting agent to dentin. The eight primers evaluated were cytochrome c aqueous solutions, four with 35 wt% 2-hydroxyethyl methacrylate (HEMA) and four without. The concentrations of cytochrome c in the primers were 0, 0.01, 0.1, and 1[corrected] micromol/g. The luting agent (Super-Bond C&B) consisted of methyl methacrylate (MMA), 4-methacryloyloxyethyl trimellitate anhydride (4-META), and tri-n-butylborane (TBB) initiator. Bovine dentin surfaces were flattened, etched with an aqueous solution of 10 wt% phosphoric acid, primed, and then bonded with stainless steel rods. After 1-day immersion in water, tensile testing revealed that the bond strength was influenced by the application of cytochrome c and HEMA. The maximum bond strength of 24.6 MPa was recorded with aqueous HEMA primer containing 10 micromol/g cytochrome c. This bonding technique, combining oxidoreductase with Super-Bond C&B, may potentially be applied for seating resin-bonded restorations.

Animals↗
PubMedDate not supplied

Substrate specificity of rat sera IgG antibodies with peroxidase and oxidoreductase activities.

We have recently shown that intact IgGs from the sera of healthy Wistar rats oxidize 3,3'-diaminobenzidine (DAB) in the presence and in the absence of H(2)O(2) similar to horseradish peroxidase (HRP). Here we demonstrate for the first time that the peroxidase and oxidoreductase activities of IgGs can efficiently oxidize not only DAB but also o-phenylendiamine, phenol, p-dihydroquinone, alpha-naphthol, and NADH but, in contrast to HRP, cannot oxidize adrenalin. In contrast to IgGs, HRP cannot oxidize phenol, p-dihydroquinone, or alpha-naphthol in the absence of H(2)O(2). In contrast to plant and mammalian peroxidases, IgGs were more universal in their metal dependence. The specific wide repertoire of polyclonal peroxidase and oxidoreductase IgGs oxidizing various substances could play an important role in protecting the organism from oxidative stress and serve as an additional natural system destroying different toxic, carcinogenic, and mutagenic compounds.

Animals↗
PubMed1992

Distribution of estradiol-17 beta hydroxysteroid oxidoreductase in the urogenital tract of control and neonatally estrogenized male mice: immunohistochemical, enzymehistochemical, and biochemical study.

The present study was conducted to investigate the regional distribution of the enzymes catalyzing the interconversion of the hydroxyl and carbonyl groups at C-17 of the estrogen molecule within the male urogenital tract of adult mouse and to test the hypothesis, whether regional differences in the distribution are critical for estrogen responses. The highest ratios of NADPH-dependent 3H-estrogen reduction to oxidation at C-17 of cell-free homogenates were obtained from coagulating gland and seminal vesicle as well as from the prostatic and lower intrapelvic urethra, which are considered the most estrogen-sensitive parts of the male urogenital tract. Both NADP- and NAD-dependent oxidation of 3H-17 beta-estradiol were low or nondetectable at these sites. The epithelium of the lower and prostatic urethra as well as the periurethral collecting ducts were stained with the antibody prepared against human placental 17 beta-hydroxysteroid oxidoreductase. The NAD-dependent 3H-estradiol-17 beta oxidase activity was highest in the bladder epithelium, and the activity declined sharply in the urinary tract from the bladder downward. The lowest detectable activities were found in vas deferens and prostate (combined ventral and dorsolateral lobes). The uneven distribution of estradiol-17 beta oxidase activity may provide additional explanation for the regional differences of estrogen responses. The NADPH-dependent 17 beta-reduction of estrone and the immunohistochemical staining of the human placental estradiol-17 beta oxidoreductase antigenicity were not significantly altered after neonatal estrogenization. These findings do not lend any support to the idea that the increased estrogen sensitivity observed after neonatal estrogenization is associated with changes in 17 beta-oxidoreduction. However, the possibility remains that there are specific sites (e.g., epithelium of prostatic urethra and collecting ducts) in which the changes in 17 beta-oxidoreduction of estrogen does play a role in the regulation of estrogen action.

17-Hydroxysteroid Dehydrogenases↗
PubMed1993

Inhibition of NAD(P)H:quinone acceptor oxidoreductase by flavones: a structure-activity study.

A structure-activity study was carried out to determine the important regions of baicalein and oroxylin A, two flavones isolated from the Chinese herb Scutellariae radix, in inhibiting NAD(P)H:quinone acceptor oxidoreductase (EC 1.6.99.2; DT-diaphorase). This quinone reductase is a vitamin K reductase. It is a target for and has been used as a model enzyme to investigate the mode of action of oral anticoagulants. The two flavones were found to inhibit this quinone reductase in nanomolar ranges. The 5-hydroxyl, 7-hydroxyl, 8-hydroxyl, and 2-phenyl groups of these flavones were found to be important for their inhibition of the enzyme. The inhibition profiles of the flavones on the NADH-menadione reductase activity, the NADH-potassium ferricyanide reductase activity, and the NADH-methyl red reductase activity of this enzyme were different. Therefore, even though the flavones were found to be competitive inhibitors with respect to NADH, they probably did not inhibit the enzyme by binding to the nicotinamide nucleotide binding site. Inhibition kinetic studies which indicated that these compounds bound to different sites than those for dicoumarol and phenindone were performed. These results indicate that these flavones are a new type of inhibitor of NAD(P)H:quinone acceptor oxidoreductase and potentially useful as anticoagulant drugs.

Azo Compounds↗
PubMed1994

Fractionation of liver microsomes with polyethylene glycol and purification of NADH-cytochrome b5 oxidoreductase and cytochrome b5.

A simplified, rapid procedure for the purification of NADH-cytochrome b5 oxidoreductase and cytochrome b5 from either rat or rabbit liver is described. Microsomes were prepared by fractionation with polyethylene glycol and solubilized with Triton X-100. Cytochrome b5 was purified by a two-column procedure, anion exchange chromatography using DEAE-cellulose, and hydrophobic chromatography on phenyl-Sepharose. The final preparation of cytochrome b5 was purified more than a 120-fold from rat or rabbit liver microsomes, with specific content of about 50 nmol per mg protein, and overall yield of 22 to 32%. Only a single band with mol wt of 18,600 was found on sodium dodecyl sulfate (SDS)-gels or on Western blots using a polyclonal antibody raised against the purified b5. NADH-cytochrome b5 oxidoreductase was purified by a three-column procedure, DEAE-cellulose, hydroxylapatite, and ADP-agarose. The final product was purified more than 400-fold from rat or rabbit liver microsomes with a yield of about 25% and final specific activity of about 1600 mumol ferricyanide reduced per minute per milligram of protein. A single band with mol wt of 33, 100 was found on SDS-gels. The reductase catalyzed reduction of ferricyanide, dichlorophenol-indophenol, and cytochrome b5. Cytochrome c was reduced in the presence of reductase plus cytochrome b5, and this was inhibited by the anti-b5 IgG. The reductase catalyzed a rapid rate of reduction of ferric-ATP, which was slightly elevated by cytochrome b5. Ferric-histidine and ferric-ammonium sulfate were slowly reduced by reductase; addition of cytochrome b5 markedly stimulated reduction of these ferric complexes but inhibited reduction of ferric-EDTA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Transcriptional regulation of the TATA-less NADPH cytochrome P-450 oxidoreductase gene.

Multiple cis-acting DNA sequences regulating expression of the rat liver NADPH-cytochrome P-450 oxidoreductase gene have been identified in transient transfection assays using promoter deletion constructs linked to the chloramphenicol acetyl transferase gene. The TATA-less promoter possesses nine GC-boxes which contain the consensus sequence for the transcription factor Sp1. While loss of the seven distal GC-boxes had minimal effect on transcriptional activity, deletion of the next 35 bp, from -206 to -172, resulted in approximately 90% loss of promoter activity. Contained within this region is an Sp1 binding site indicating that either (1) this particular consensus sequence was essential for transcription, (2) the two proximal GC boxes act in concert, or (3) a yet unidentified regulatory element resides within this 35-bp stretch. In addition, transfection experiments demonstrated that two separate distal regions (-622 to -1167 and -1500 to -2300) contain negative regulatory elements which down-regulate gene transcription in a position-independent manner. Mobility-shift analyses and DNase footprinting identified sequences in the proximal region of the promoter that bound proteins present in nuclear extracts. Four protected segments were observed within the first 100 bp upstream of the transcription start site; these include (1) the region encompassing the transcription start site (-7 to +4), (2) the region normally occupied by a TATA-box (-38 to -18), (3) the bases from -78 to -60 which contain the regulatory element CACC, and (4) bases -105 to -92 which include an Sp1 binding site. Hence, regulation of the NADPH-cytochrome P-450 oxidoreductase gene is controlled by both positive and negative regulatory elements, and, of the nine Sp1 consensus sites, the two proximal sites are sufficient to support basal transcription.

Animals↗
PubMed1996

Stable expression of human cytochrome P450 3A4 in conjunction with human NADPH-cytochrome P450 oxidoreductase in V79 Chinese hamster cells.

V79 Chinese hamster cells were constructed for stable expression of human cytochrome P450 3A4 with and without coexpression of human NADPH-cytochrome P450 oxidoreductase. Expression of the cDNAs was shown by Northern and Western analyses. Activity was tested by 6 beta-hydroxylation of testosterone for cytochrome P450 3A4 and by cytochrome c reduction for NADPH-cytochrome P450 reductase. Five V79 cell lines were obtained expressing cytochrome P450 3A4, human NADPH-cytochrome P450 oxidoreductase, and both. Cytochrome P450 3A4 activity depended highly on cytochrome P450 reductase activity, with lowest activity when only the parental Chinese hamster cytochrome P450 reductase was present, 5- and 10-fold higher when coexpressed with the human NADPH-cytochrome P450 reductase. Correspondingly, cytotoxic and genotoxic potency of aflatoxin B1 was increased by orders of magnitudes when human cytochrome P450 3A4 was coexpressed with the human NADPH-cytochrome P450 reductase. The effect of NADPH-cytochrome P450 reductase coexpression on cytochrome P450 3A4 activity was also tested by nifedipine oxidation and midazolam hydroxylation. Nifedipine oxidation was increased about 10-fold, 1-hydroxylation of midazolam and 4-hydroxylation of midazolam were increased 15-fold.

Aflatoxin B1↗
PubMed1997

Di-fluoresceinthiocarbamyl-insulin: a fluorescent substrate for the assay of protein disulfide oxidoreductase activity.

We have developed a novel method for the continuous assay of protein disulfide oxidoreductase activity using as substrate bovine pancreas insulin in which both N-terminal amino groups are chemically modified with fluorescein isothiocyanate. The reduction of intercatenary disulfide bonds of di-fluoresceinthiocarbamyl-insulin with dithiothreitol initially lowers but subsequently enhances the emission intensity. In this biphasic kinetics, the rate of increase is sensitive enough for the estimation of Escherichia coli thioredoxin concentrations from 5 nM (0.06 microgram/ml) to 500 nM (6 micrograms/ml). Neither changes of pH over a range of 6.2 to 8.4 nor neutral salts (K+, Mg2+, and Ca2+) at concentrations lower than 100 mM affect this simple reaction system. Moreover, the fluorometric method is functional for measuring the reductive capacity of Brassica napus protein disulfide isomerase. Hence, a highly reproducible and accurate one-state assay for protein disulfide oxidoreductase activity not only greatly improves the sensitivity compared to the commonly used turbidimetric assay but also represents a reliable alternative to assays based on accessory enzymes or radiolabeled substrates.

Feasibility Studies↗
PubMed1993

Purification of a 57kDa nuclear matrix protein associated with thiol:protein-disulfide oxidoreductase and phospholipase C activities.

Proteins of the internal nuclear matrix from chicken liver were fractionated, by chromatographic procedures, in non denaturing conditions. At least two fractions were present with phosphatidylinositol-specific phospholipase C and three with thiol:protein-disulfide oxidoreductase activity. A 57kDa protein was isolated which copurified with both these activities. Partial amino acid sequences showed a high degree of homology with a cytosolic protein previously identified as a phospholipase C and with a microsomal protein identified as a thiol:protein-disulfide oxidoreductase. Our finding leaves the question still unanswered of the real function of this protein, which for the first time has been isolated from the nuclear matrix.

Amino Acid Sequence↗
PubMed1996

Isolation of a new mouse cDNA clone: hybrid form of cytochrome P450 2b10 and NADPH-cytochrome P450 oxidoreductase.

We have isolated a novel cDNA sequence from a male mouse liver library. It consists of an open reading frame containing no stop codon of 1348 bp which share 98% similarity with the cytochrome P450 2b10 followed by 95 nucleotides sharing 88% identity with the mouse NADPH cytochrome P450 oxidoreductase. Proteins are encoded by the opposite DNA strands. Genomic amplification excludes a library artefact or a de novo recombination event. RT-PCR analyses revealed expression of this clone in the liver of male and female mice as well as in kidney, lung and intestine. This cDNA was not, however, induced by phenobarbital. Preliminary results indicate that this cDNA could span more than 2.5 kb. This study is the first description of a cytochrome P450 cDNA sequence encoding part of both a cytochrome P450 and the NADPH cytochrome P450 oxidoreductase in mammalian liver.

Amino Acid Sequence↗