Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

NADH:ubiquinone reductase, the respiratory chain complex I of mitochondria, consists of some 25 nuclear-encoded and seven mitochondrially encoded subunits, and contains as redox groups one FMN, probably one internal ubiquinone and at least four iron-sulphur clusters. We are studying the assembly of the enzyme in Neurospora crassa. The flux of radioactivity in cells that were pulse-labelled with [35S]methionine was followed through immunoprecipitable assembly intermediates into the holoenzyme. Labelled polypeptides were observed to accumulate transiently in a Mr 350,000 intermediate complex. This complex contains all mitochondrially encoded subunits of the enzyme as well as subunits encoded in the nucleus that have no homologous counterparts in a small, merely nuclear-encoded form of the NADH:ubiquinone reductase made by Neurospora crassa cells poisoned with chloramphenicol. With regard to their subunit compositions, the assembly intermediate and small NADH:ubiquinone reductase complement each other almost perfectly to give the subunit composition of the large complex I. These results suggest that two pathways exist in the assembly of complex I that independently lead to the preassembly of two major parts, which subsequently join to form the complex. One preassembled part is related to the small form of NADH:ubiquinone reductase and contributes most of the nuclear-encoded subunits, FMN, three iron-sulphur clusters and the site for the internal ubiquinone. The other part is the assembly intermediate and contributes all mitochondrially encoded subunits, one iron-sulphur cluster and the catalytic site for the substrate ubiquinone. We discuss the results with regard to the evolution of the electron pathway through complex I.
J Mol Biol 1990 Jun 20
PMID:Assembly of NADH: ubiquinone reductase (complex I) in Neurospora mitochondria. Independent pathways of nuclear-encoded and mitochondrially encoded subunits. 214 52

We have previously shown that human placental estradiol-17 beta dehydrogenase (EC 1.1.1.62; 17 beta-EDH) catalyzes the conversion of estradiol-17 beta to estrone and stereospecifically reduces NAD+ to [4-pro-S]NADH, [( 4-B]NADH). Subsequently, this enzyme was found to reduce the ketone function at C-20 of progesterone, and evidence indicates that both activities reside at the same active site. This study was done to further elucidate spatial arrangements of cofactor and the 21-carbon substrate as they bind at the active site. The cofactor, [4B-3H]NADPH, was generated with homogeneous 17 beta-EDH from term human placenta, utilizing [17 alpha-3H]estradiol-17 beta and NADP+. The resulting [4B-3H]NADPH was then purified by ion exchange chromatography and was separately incubated (24.4 microM) with a large molar excess of progesterone (150 microM) as substrate in the presence of the enzyme. Following incubation, the steroid reactants and products were extracted, separated by high-performance liquid chromatography and quantitated as to mass and tritium content. Oxidized and reduced cofactor were separated by ion-exchange chromatography and similarly quantitated. In all incubations, equimolar amounts of 20 alpha-hydroxy-4-pregnen-3-one (20 alpha-OHP) and NADP+ were obtained. Radioactivity was stoichiometrically transferred from [4B-3H]NADPH to the steroid product [( 3H]20 alpha-OHP). These results further substantiate a single active site for both 17 beta- and 20 alpha-dehydrogenation enzyme activities. In addition, the enzyme is B-side specific, catalyzing the transfer of the 4B-hydrogen from the dihydronicotinamide moiety of the cofactor, for both C-18 and C-21 steroid substrates. Since the 20 alpha-dehydrogenation by other enzyme sources has always been demonstrated to be an A-side specific reaction, this observation represents an important exception to the Alworth-Bentley rules of enzyme stereospecificity.
J Steroid Biochem Mol Biol 1990 Sep
PMID:Stereospecificity of hydrogen transfer between progesterone and cofactor by human placental estradiol-17 beta dehydrogenase. 214 72

An 8kb segment of DNA from the 58/59 min region of the E. coli chromosome, which complements the defect of a mutant devoid of hydrogenase 3 activity, has been sequenced. Eight open reading frames were identified which are arranged in a transcriptional unit; all open reading frames were transcribed and translated in vivo in a T7 promoter/polymerase system. Analysis of the amino acid sequences derived from the nucleic acid sequences revealed that one of them, open reading frame 5 (ORF5), exhibits significant sequence similarity to conserved regions of the large subunit from Ni/Fe hydrogenases. Two of the open reading frames (orf2, orf6) code for proteins apparently carrying iron-sulphur clusters of the 4Fe/4S ferredoxin type. The product of one of the open reading frames, orf7, displays extensive sequence similarity with protein G from the chloroplast electron transport chain. ORF3 and ORF4, on the other hand, are extremely hydrophobic proteins with nine and six putative transmembrane helices, respectively. Over a limited hydrophilic sequence stretch, bordered by putative transmembrane areas, ORF3 and ORF4 exhibit homology with subunits 4 and 1 of mitochondrial and plastid NADH-ubiquinol oxidoreductases, respectively. The operon described, therefore, appears to comprise genes for redox carriers linking formate oxidation to proton reduction and for a hydrogenase of hitherto unique composition.
Mol Microbiol 1990 Feb
PMID:Nucleotide sequence and expression of an operon in Escherichia coli coding for formate hydrogenlyase components. 218 44

Biliverdin reductase is the dual nucleotide-dependent cytosolic enzyme that converts biliverdin to the bile pigment, bilirubin, and displays extensive microheterogeneity in rat organs. The enzyme is unique in having two pH optima. The present study reports on the tissue-dependent pattern of developmental expression of the reductase in rat liver and brain. When analyzed by Western immunoblotting, two closely migrating immunoreactive proteins were detected in the liver cytosol during the first 2-3 weeks after birth; the protein with greater mobility was not detected in the liver of adult aged animals (6 months old) and was present at low levels in rats during the first week of life. The faster migrating protein was not detected in the brain cytosol at any stage of development. Furthermore, in the brain the total amount of enzyme protein increased as the animal matured, whereas in the liver the enzyme protein level decreased with age. When the purified enzyme was analyzed, age-related changes in the variant composition of the enzyme in the liver were noted. Although in both adult and newborn animals (14 days old) the purified enzyme, when subjected to isoelectric focusing, separates into five net charge forms (pl 6.23, 5.91, 5.76, 5.61, and 5.48), the relative abundance of the variants notably differed in the two preparations. In addition, when the purified preparations were subjected to two-dimensional electrophoresis, although both purified preparations separate into three molecular weight forms (Mr 30,400, 30,700, and 31,400) one species (Mr 31,400, pl = 5.77), which was very prominently expressed in the newborn, was essentially absent in the adult. Biliverdin reductase activity of the liver cytosol with both NADPH (pH 8.7) and NADH (pH 6.7) exhibited developmental changes, with the activity increasing after birth, reaching a peak on day 14, and decreasing to low levels in the adult. The existence of a close correlation between development of biliverdin reductase activity in the brain and liver and that of heme oxygenase in these organs is noted. The suggestion is made that the reductase is not a passive component of the heme degradation pathway; rather, its activity could become limiting in the elimination of heme degradation products.
Mol Pharmacol 1990 Oct
PMID:Multiple forms of biliverdin reductase: age-related change in pattern of expression in rat liver and brain. 223 89

Menadione bisulfite is a hepatotoxicant that damages periportal regions of the lobule in perfused liver in an oxygen-dependent manner. The effect of ethanol on menadione bisulfite toxicity was examined in perfused rat liver. Addition of menadione bisulfite (3 mM) alone to the perfusate increased oxygen uptake by 20-30 mumols/g/hr. Lactate dehydrogenase was released into the effluent after 60 min of perfusion and reached values around 100 units/g/hr. Under these conditions, trypan blue was taken up exclusively in periportal regions of the liver lobule; 44% of periportal cells were stained. In the presence of ethanol, maximal increases in oxygen uptake due to menadione bisulfite were much larger (about 90 mumols/g/hr), and lactate dehydrogenase release occurred earlier and reached higher maximal values (330 units/g/hr). Trypan blue staining was also more extensive; 90% of periportal cells were stained. The effect of ethanol on menadione bisulfite-induced oxygen uptake required metabolism via alcohol dehydrogenase (ADH), because ethanol increased oxygen uptake due to menadione bisulfite from 44 to 81 mumols/g/hr in deermice with ADH but had no effect in deermice lacking ADH. Other agents that increase NADH (xylitol and 2-ethyl-1-hexanol) also potentiated the stimulation of oxygen uptake due to menadione bisulfite, suggesting that ethanol was working by increasing the NADH redox state. Cyanide abolished the increase in oxygen uptake due to menadione bisulfite, both in the absence and in the presence of ethanol, supporting the hypothesis that the effect of ethanol on menadione bisulfite-mediated oxygen uptake involves the mitochondrial respiratory chain. Further, the stimulation of oxygen uptake by menadione bisulfite in isolated mitochondria was enhanced when matrix NADH was increased by addition of beta-hydroxybutyrate. These data indicate that ethanol potentiates oxygen uptake and toxicity due to menadione bisulfite most likely by generation of NADH for redox cycling of this model quinone.
Mol Pharmacol 1990 Dec
PMID:Ethanol potentiates oxygen uptake and toxicity due to menadione bisulfite in perfused rat liver. 225 Jun 68

We asked whether the mitochondrial T-urf13 gene, associated with the male sterility phenotype of T cytoplasm in maize, can be expressed in Saccharomyces cerevisiae and whether this expression can mimic the effects observed in maize. We introduced the universal code equivalent of the T-urf13 gene into the S. cerevisiae nucleus by transformation and directed its translation product into mitochondria by means of a fusion with the targeting presequence from Neurospora crassa AT-Pase subunit 9. We show that expression of the universal code equivalent of the T-urf13 gene in the yeast nucleus does indeed mimic its effects in maize: respiratory growth of yeast is inhibited, respiration-deficient cytoplasmic mutants accumulate and NADH oxidation of isolated mitochondria is uncoupled. All these effects are observed only if the mitochondrial targeting peptide and methomyl or HmT toxin are present.
Mol Gen Genet 1990 Aug
PMID:Expression in Saccharomyces cerevisiae of a gene associated with cytoplasmic male sterility from maize: respiratory dysfunction and uncoupling of yeast mitochondria. 225 41

Crude extracts from a number of helminths including Schistosoma intercalatum and Fasciola hepatica were able to detoxify known aldehydic products of lipid peroxidation. A major route for alk-2-enal and alka-2,4-dienal detoxification in parasitic helminths was via glutathione conjugation and glutathione transferase appeared to be responsible for the activity. As yet uncharacterised NADPH-linked systems may provide an important secondary pathway for detoxification of alk-2-enals and alka-2,4-dienals in parasitic helminths. The free-living nematode Panagrellus redivivus had higher active NADH/NADPH-linked aldehyde reduction systems compared to parasitic helminths. The NADH linked and NADPH linked reductions in P. redivivus were mitochondrial and cytosolic activities respectively. NADH/NADPH-linked systems may be responsible for alkanal reduction in helminths as there is no evidence of conjugation of alkanals with glutathione. P. redivivus and Haemonchus contortus were also able to oxidise aldehydes via NAD/NADP-linked systems.
Mol Biochem Parasitol
PMID:Strategies for detoxification of aldehydic products of lipid peroxidation in helminths. 227 Jan 3

Here we report on the detection of multiple net-charge and molecular mass variants of biliverdin reductase in the rat kidney and describe selective changes in the tissue profile of the variants after bromobenzene treatment (2 mmol/kg, subcutaneously, 24 hr). Using two-dimensional electrophoresis and isoelectric focusing, two major molecular mass species, Mr 30,400 and 30,700, a minor form of Mr 31,400, and five net-charge groups of pI = 6.23, 5.91, 5.77, 5.61, and 5.48 were detected; the net-charge variants with pI = 5.61 and 5.77 were the most abundant forms. The Mr 30,400 form was the main component of two isoelectric focusing bands with pI = 6.23 and 5.91, and the relative amounts of these net-charge variants was severely decreased in the kidneys of bromobenzene-treated rats. The effect of bromobenzene in vivo could not be duplicated by in vitro experiments involving the direct treatment of purified enzyme with bromobenzene, or incubation of the purified preparation with bromobenzene in the presence of a NADPH-dependent microsomal drug-metabolizing system. Bromobenzene treatment did not alter the immunochemical properties of biliverdin reductase variants, as judged by the similarity of isoelectric focusing patterns of preparations on a Western blot using antibody raised against a rat liver total biliverdin reductase preparation. The treatment, however, caused an alteration in the kinetic properties of the enzyme, and the activity with NADH appeared to be selectively decreased. The possible mechanisms involved in the expression of multiple forms of the reductase and the biological significance of the multiplicity, as well as the change in composition caused by bromobenzene, are discussed.
Mol Pharmacol 1990 Jan
PMID:Bromobenzene-mediated alteration in activity and electrophoretic pattern of biliverdin reductase variants in rat kidney. 230 45

The effects of culture variables on the specific content and activity of various enzymes of the drug metabolizing system were assessed in colon tumor cell line LS174T. The NADH reduced cytochrome b5 (cyt b5)4 spectrum of these cells was similar to rat liver cyt b5. When released from the membrane by trypsin and concentrated, the cyt b5 was found to cross react with rabbit antibody to rat liver cyt b5 and human liver cyt b5. The enzyme activities were found stable over limited cell passages with control values of 0.03 and 0.13 mumol/min/mg protein for NADPH and NADH cytochrome c (cyt c) reducing activity, 0.05 nmol cyt b5 and 0.013 nmol cytochrome P450 per milligram of microsomal protein. Phenobarbital/hydrocortisone showed a consistent, but not always significant increase in the NADPH and NADH cyt c reduction and benzanthracene an increase in the NADH cyt c reducing activity and cyt b5 content. Griseofulvin lowered the NADH cyt c reducing activity. Delta-aminolevulinic acid (0.5 mM) caused a significant decrease in the specific activity of all enzymes, as judged by a student's t test, with a p less than 0.001.
Mol Cell Biochem 1990 Mar 27
PMID:Human colon tumor cell line LS174T drug metabolizing system. 234 45

In the presence of Mg2+, pure glutamate dehydrogenase is more reactive with NADPH than with NADH and is markedly activated by elevations in the ADP/ATP ratio or the addition of leucine. Because these are properties of glutamate dehydrogenase in mitochondria but not properties of the pure enzyme studied in the absence of Mg2+, Mg2+ could be a ligand that confers upon glutamate dehydrogenase the regulatory properties of this enzyme found in situ. In the absence of the allosteric activators ADP, leucine, or succinyl-CoA, Mg2+ is an inhibitor and increases product inhibition by alpha-ketoglutarate in the forward reaction and substrate inhibition by alpha-ketoglutarate in the reverse reaction. However, the allosteric activators convert Mg2+ from an inhibitor into an activator of the forward reaction. In the reverse reaction, ADP also converts Mg2+ from an inhibitor into an activator and leucine eliminates inhibition by Mg2+. Because Mg2+ is an inhibitor in the absence of activator that also increases inhibition by alpha-ketoglutarate, whereas in the presence of activator Mg2+ has no effect or is itself an activator, Mg2+ magnifies the effect of the activator, and magnification increases with increases in the concentration of alpha-ketoglutarate. Leucine and its analog 2-aminobicyclo (2.2.1) heptane 2-carboxylic acid (BCH) have almost identical effects on both human and bovine glutamate dehydrogenase in both the presence and absence of Mg2+. However, advantages of BCH over leucine as a potential pharmacological activator of glutamate dehydrogenase are that BCH is not metabolized and, unlike leucine, BCH does not inhibit ornithine transcarbamylase. Isoleucine and valine alone have little effect on human glutamate dehydrogenase, but isoleucine slightly inhibits the enzyme in the presence of leucine.
Mol Pharmacol 1990 Jun
PMID:Regulation of glutamate dehydrogenase by Mg2+ and magnification of leucine activation by Mg2+. 235 6


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