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PubMed1984

The sequence of the gene for cytochrome c oxidase subunit I, a frameshift containing gene for cytochrome c oxidase subunit II and seven unassigned reading frames in Trypanosoma brucei mitochondrial maxi-circle DNA.

A 9.2 kb segment of the maxi-circle of Trypanosoma brucei mitochondrial DNA contains the genes for cytochrome c oxidase subunits I and II (coxI and coxII) and seven Unassigned Reading Frames ("URFs"). The genes for coxI and coxII display considerable homology at the aminoacid level (38 and 25%, respectively) to the corresponding genes in fungal and mammalian mtDNA, the only striking point of divergence being an unusually high cysteine content (about 4.5%). The reading frame coding for cytochrome c oxidase subunit II is discontinuous: the C-terminal portion of about 40 aminoacids, is present in the DNA-sequence in a -1 reading frame with respect to the N-terminal moiety. URF5, 8 and 10, show a low but distinct homology (about 20%) to mammalian mitochondrial URF-1, 4 and 5, respectively. In URF5, the first AUG is found at codon 145, whereas extensive homology to mammalian URF-1 sequences occurs upstream of this position. The possibility exists that UUG can serve as an initiator codon. URF7 and URF9 have a highly unusual aminoacid composition and do not possess AUG or UUG initiator codons. These URFs probably do not have a protein-coding function. The segment does not contain conventional tRNA genes.

Amino Acid Sequence↗
PubMed1998

The role of the alternative oxidase in stabilizing the in vivo reduction state of the ubiquinone pool and the activation state of the alternative oxidase

A possible function for the alternative (nonphosphorylating) pathway is to stabilize the reduction state of the ubiquinone pool (Qr/Qt), thereby avoiding an increase in free radical production. If the Qr/Qt were stabilized by the alternative pathway, then Qr/Qt should be less stable when the alternative pathway is blocked. Qr/Qt increased when we exposed roots of Poa annua (L.) to increasing concentrations of KCN (an inhibitor of the cytochrome pathway). However, when salicylhydroxamic acid, an inhibitor of the alternative pathway, was added at the same time, Qr/Qt increased significantly more. Therefore, we conclude that the alternative pathway stabilizes Qr/Qt. Salicylhydroxamic acid increasingly inhibited respiration with increasing concentrations of KCN. In the experiments described here the alternative oxidase protein was invariably in its reduced (high-activity) state. Therefore, changes in the reduction state of the alternative oxidase cannot account for an increase in activity of the alternative pathway upon titration with KCN. The pyruvate concentration in intact roots increased only after the alternative pathway was blocked or the cytochrome pathway was severely inhibited. The significance of the pyruvate concentration and Qr/Qt on the activity of the alternative pathway in intact roots is discussed.

Journal Article↗
PubMed1987

6-Hydroxy-D-nicotine oxidase of Arthrobacter oxidans. Gene structure of the flavoenzyme and its relationship to 6-hydroxy-L-nicotine oxidase.

The nucleotide sequence of the 6-hydroxy-D-nicotine oxidase (6-HDNO) gene of Arthrobacter oxidans is presented. This covalently flavinylated enzyme specifically oxidizes 6-hydroxy-D-nicotine to 6-hydroxy-N-methylmyosmine. Coinduced in the presence of nicotine is a 6-hydroxy-L-nicotine-specific enzyme, 6-hydroxy-L-nicotine oxidase (6-HLNO), with FAD noncovalently bound to the apoprotein. A comparison of the nucleotide-derived amino acid sequence of the 6-HDNO with the amino acid sequence data obtained from the purified 6-HLNO polypeptide suggests that the two enantiozymes expressed within the same cell are genetically unrelated. This conclusion is supported by the finding that the FAD-binding sites of the two enzymes are different. 6-HLNO exhibits at the amino-terminus of the polypeptide chain a dinucleotide-binding site characteristic for many other FAD- and NAD(P)-dependent enzymes. No such sequence was found in the nucleotide-derived amino acid sequence of 6-HDNO.

Amino Acid Sequence↗
PubMed1965

PHOTOCHEMICAL ACTION SPECTRUM OF THE TERMINAL OXIDASE OF MIXED FUNCTION OXIDASE SYSTEMS.

The reversal of the carbon monoxide inhibition by bands of monochromatic light was determined for the oxidative demethylation of codeine and monomethyl-4-aminopyrine and the hydroxylation of acetanilide by rat liver microsomes and for the hydroxylation of 17-hydroxyprogesterone at carbon-21 by bovine adrenocortical microsomes. Maximum reversal occurred at 450 millimicrons, the light absorption maximum of the CO compound of the CO-binding pigment of microsomes. The agreement between photochemical action spectrum and spectrophotometric difference spectrum supports the conclusion that the CO-binding pigment is the terminal oxidase of mixed function oxidase systems of mammals.

Acetanilides↗
PubMed1982

Rapid, modified oxidase test for oxidase-variable bacterial isolates.

A modified oxidase reagent, 1% tetramethyl-p-phenylenediamine in dimethyl sulfoxide, proved superior to the routinely used 1% aqueous tetramethyl-p-phenylenediamine dihydrochloride in detecting weakly oxidase-positive gram-negative bacteria after 24 h of growth on agar media (40 of 40 positive versus 22 of 40 positive). The bacterial inoculum was obtained with a cotton-tipped swab instead of a loop or wooden applicator, and the reaction required less than 15 s.

Bacteria↗
PubMed1978

Electronic state of heme in cytochrome oxidase III. The magnetic susceptibility of beef heart cytochrome oxidase and some of its derivatives from 7-200 K. Direct evidence for an antiferromagnetically coupled Fe (III)/Cu (II) pair.

The temperature dependence of the paramagnetic susceptibility of cytochrome oxidase and some of its derivatives has been measured from 7 to 200 K. The results obtained for the fully oxidized (resting) enzyme correspond exactly to the requirements of the model recently proposed by Palmer et al. (Palmer, G., Babcock, G. T., and Vickery, L. E. (1976) Proc. Natl. Acad. Sci. U. S. A. 73, 2206-2210) in which the enzyme possesses two magnetically isolated spin S = 1/2 centers and a spin-coupled S = 2 center. The S = 2 center paramagnetism has been interpreted as arising from a [cytochrome a33+(S = 5/2)--Cuu2+(S = 1/2)] antiferromagnetically coupled iron.copper binuclear complex of total spin S = 2 with -J greater than or equal to 200 cm-1. In addition, the wide temperature range used in the present studies has permitted an analysis of present and other available data (T less than 4K measurements) which readily accommodates results from this and other laboratories (Moss, T.H., Shapiro, E., King, T.E., Beinert, H., and Hartzell, C. R. (1978) J. Biol. Chem 253, 8072-8073) so that a fully consistent picture of the magnetic centers in cytochrome oxidase now appears to be available. Furthermore, anomalous magnetic behavior for the oxidized enzyme.cyanide complex has been interpreted in terms of an antiferromagnetic exchange interaction operating in the binuclear complex [cytochrome a33+.CN-(S = 1/2)--Cuu2+(S = 1/2)] with -J congruent to 40 cm-1. A structural model for the [cytochrome a3(3+)-bridge-CUu2+] center is advanced in which an imidazolate ion serves as the bridging ligand in a manner similar to that found in superoxide dismutase.

Animals↗
PubMed1979

[Activity of delta-aminolevulinic synthetase, cytochrome oxidase and levels of the mixed function oxidase system during experimental protein malnutrition. Response to re-alimentation].

Activities of delta amino levulinic synthetase (DALS), cytochrome oxidase (E. C. 1.9.3.1.), NADH cytochrome b5 reductase (NADH red.), NADPH cytochrome P450 reductase (NADPH red.), contents of cytochrome P450 (cyt. P450) and cytochrome b5 (cyt. b5), and levels of hemoglobin and hematocrit were studied in three groups of rats: a) malnourished, b) during recovery from malnutrition, and c) controls. During severe protein malnutrition blood levels of hemoglobin and hematocrit were found to be decreased as well as DALS's activity in homogenized bone marrow and liver. The activity of NADH red, and contents of cyt. P.450 and cyt. b5 in hepatic microsomes were also found significantly depressed. The microsomal activity of NADPH red. as well as mitochondrial cytochrome oxidase did not present significant changes, since values obtained in malnourished rats were similar to those found for the control group. While recovering from malnutrition, when rats were fed a casein based diet (10 NDpCalo/o) supplemented with Fe and Cu, the hepatic enzymatic activities, the cytochrome contents of P450 and b5, and hematocrit experienced a spectacular increase, reaching towards the end of the refeeding period values which could be compared to those found in the control group. Nevertheless, DALS' activity in homogenized bone marrow and hemoglobin levels remained low. Results are discussed in relation to depressed activities and contents of enzymes, coenzymes, metabolites and subtrates involved in the hemoglobin synthesis in the rat bone marrow, during recovery from malnutrition.

5-Aminolevulinate Synthetase↗
PubMedDate not supplied

[Oxidative phosphorylation, NADH-oxidase and succinate oxidase activity in testicular mitochondria of rats with alloxan diabetes].

Decrease in V4P, V3 and VP, in coefficient of respiratory control, in the ratio ADP:0 as well as an increase in duration of phosphorylation of ADP involved in oxidation of succinate were found in testes mitochondria from rats with alloxan diabetes (content of glucose 20 +/- 2 mmol/L in blood plasma). If a mixture of malate and glutamate was used as a substrate of oxidation, the rate of mitochondrial respiration and coefficient of respiratory control were decreased in testes of diabetic rats under conditions of all the metabolic states studied. At the same time, sensitivity of NADH-oxidase and succinate oxidase systems to controlled heating (28 degrees) was distinctly decreased in the testes mitochondrial membranes of the impaired animals as compared with controls. The data obtained suggest that distinct functional and, apparently, structure alterations occurred in the testes mitochondrial membranes of rats with alloxan diabetes.

Animals↗
PubMed1997

Specific and amplified current responses to histidine and histamine using immobilized copper-monoamine oxidase membrane electrode, based on novel ascorbate oxidase activity induced by exogenous ligands.

Upon the addition of histidine and histamine, the copper containing monoamine oxidase (MAO) catalyzes the oxidation of L-ascorbic acid (AsA) by dissolved oxygen, in which the consumed oxygen was finally converted to hydrogen peroxide, according to Michaelis-Menten kinetics (Km) = 1.97 mM, upon the addition of 5 x 10(-5) M L-histidine at 35 degrees C and pH 8.5). The amount of oxygen consumption depended on the amount of histidine and histamine added, and specific responses over other amines were observed when the oxygen electrode modified with immobilized MAO membrane was used in the 0.1 M Tris buffer containing AsA. The calibration curves of L-histidine and histamine at 4 mM AsA exhibit linearity in the concentration range from 5 x 10(-7) to 5 x 10(-5) M L-histidine and 5 x 10(-6) to 1 x 10(-8) M histamine, with detection limit of 3 x 10(-7) M L-histidine and 3 x 10(-6) M histamine, respectively. The ESR signal of copper(II) in active site of MAO at 77K was apparently changed upon the addition of L-histidine and histamine indicating that exogenous histidine and histamine bound to the copper site of enzyme and lead to the structural change in active site.

Animals↗
PubMed1990

Monoamine oxidase and semicarbazide-sensitive amine oxidase activities in bovine eye.

The activities of MAO-A, MAO-B and the semicarbazide-sensitive amine oxidase (SSAO) were determined in bovine lens, retina, optic nerve, iris and epithelium. No activities were detected in lens but the SSAO activity was found to be rather evenly distributed in the other tissues. The SSAO activities determined with 1 microM benzylamine were about half those determined for MAO-B. MAO-A activity, measured with 5-HT as substrate, was considerably greater than those of MAO-B and SSAO, determined with 2-phenylethylamine and benzylamine, respectively, in all the eye tissues.

Amine Oxidase (Copper-Containing)↗
PubMed2005

The antioxidant anethole dithiolethione inhibits monoamine oxidase-B but not monoamine oxidase A activity in extracts of cultured astrocytes.

Anethole dithiolethione (ADT) is a clinically available, pluripotent antioxidant proposed as a neuroprotectant for Parkinson's disease (PD). Here, using extracts from cultured astrocytes, containing both monoamine oxidase (MAO) A and B activity, we demonstrate that ADT concentration-dependently inhibits MAO-B activity in a clinically relevant concentration range (0.03-30 microM, IC-50 = 0.5 microM) without affecting MAO A activity. Considering the alleged contribution of MAO activity in general, and MAO-B in particular, to oxidative stress and neurodegeneration in PD, our data further support the neuroprotective potential of ADT.

Analysis of Variance↗
PubMed1992

Increase of brain endogenous monoamine oxidase inhibitory activity (tribulin) in experimental audiogenic seizures in rats: evidence for a monoamine oxidase A inhibiting component of tribulin.

Brain tribulin activity in rats with an inherited predisposition to audiogenic epilepsy was studied after seizures of different intensity were induced by an electric bell. Weak seizures (from 0 to 2 arbitrary units) did not produce any changes in endogenous inhibitory activity towards either monoamine oxidase (MAO) A or B. Moderate seizures were characterized by increases in both MAO A and MAO B inhibitory activity (up to 1.9-fold). Complete tonic epileptiform seizures with total areflexia (4 arbitrary units) induced further augmentation (up to 2.5-fold) of MAO A but not of MAO B inhibitory activity. This dissociation between the two inhibitory activities points to the existence of a separate MAO A-inhibiting component of brain tribulin which is different from isatin.

Animals↗
PubMed2004

HPLC-based bioactivity profiling of plant extracts: a kinetic assay for the identification of monoamine oxidase-A inhibitors using human recombinant monoamine oxidase-A.

An assay for the HPLC-based search for monoamine oxidase-A (MAO-A) inhibitors in plant extracts was established. It combines human recombinant MAO-A, expressed as GST-fusion protein in yeast, with a kinetic measurement of the conversion of kynuramine to 4-hydroxyquinoline. Substrate selectivity and kinetic parameters of the GST-fusion protein were comparable to the wild-type enzyme. The applicability of the assay to HPLC-based activity profiling was tested with plant extracts spiked with small amounts of known MAO inhibitors.

Chromatography, High Pressure Liquid↗
PubMed1988

Inactivation of monoamine oxidase A by the monoamine oxidase B inactivators 1-phenylcyclopropylamine, 1-benzylcyclopropylamine, and N-cyclopropyl-alpha-methylbenzylamine.

Three known mechanism-based inactivators of beef liver mitochondrial monoamine oxidase (MAO) B are tested as inactivators of human placental mitochondrial MAO A. 1-Phenylcyclopropylamine (1-PCPA), 1-benzylcyclopropylamine (1-BCPA), and N-cyclopropyl-alpha-methylbenzylamine (N-C alpha MBA) are time-dependent irreversible inactivators of MAO A. The KI values for 1-PCPA and N-C alpha MBA, analogues of the MAO B substrate benzylamine, are much higher with MAO A than with MAO B. Evidence is presented to show that 1-PCPA inactivates MAO A by attachment to the flavin cofactor, unlike the reaction with MAO B in which 1-PCPA can attach to both a cysteine residue and the flavin [Silverman, R.B., & Zieske, P.A. (1985) Biochemistry 24, 2128-2138]. The reaction of 1-BCPA with MAO A was too slow to study in detail. N-C alpha MBA exhibits the same properties toward inactivation of MAO A that it does for inactivation of MAO B. Attachment in both cases is shown to be to one cysteine residue per enzyme molecule. The results with 1-PCPA indicate that the active site topographies of MAO A and MAO B are different. The ability of N-C alpha MBA to undergo attachment to a cysteine residue in both MAO A and MAO B may lead the way toward peptide mapping of the two isozymes in order to determine differences in their primary structures.

Benzylamines↗
PubMed2004

Analysis of mRNA transcripts from the NAD(P)H oxidase 1 (Nox1) gene. Evidence against production of the NADPH oxidase homolog-1 short (NOH-1S) transcript variant.

Recent reports indicate that NAD(P)H oxidase 1 (Nox1) mRNA undergoes alternative splicing, producing a short transcript (NOH-1S) encoding a novel H+ channel. Although the H+ transport properties of NOH-1S-transfected cells resemble those of many cells, the production of a NOH-1S protein was never documented. We characterized Nox1 transcripts in colon-derived cells and present evidence that mRNA splicing does not produce NOH-1S; rather, NOH-1S appears to be an artifact of template switching during cDNA synthesis. The NOH-1S transcript was not observed by Northern blotting, despite claims of its abundance based on RNase protection assays. The shortened cDNA was generated by avian myeloblastosis virus reverse transcriptase, but not by thermally stable reverse transcriptase under conditions that produce full-length Nox1. Analysis of shortened cDNAs detected NOH-1S sequence and other variants that differ at the alleged splice junction site. Although no appropriate RNA splicing sites were found within Nox1 to account for NOH-1S formation, we found repetitive sequence elements bordering the deleted region, which could promote intramolecular template switching during cDNA synthesis. Template switching was confirmed in vitro, where the deleted cDNA was generated by avian myeloblastosis virus reverse transcriptase from a synthetic, full-length Nox1 RNA template. A survey of the expressed sequence tags database suggests that similar switching phenomena occur between repetitive elements in other Nox family transcripts, indicating such cloning artifacts are common. In contrast, genuine RNA splicing does account for another Nox1 transcript lacking the entire exon 11, which is abundant in colon cells but encodes a protein incapable of supporting superoxide production.

Alternative Splicing↗
PubMed2005

NADH oxidase activity of rat liver xanthine dehydrogenase and xanthine oxidase-contribution for damage mechanisms.

The involvement of xanthine oxidase (XO) in some reactive oxygen species (ROS) -mediated diseases has been proposed as a result of the generation of O*- and H2O2 during hypoxanthine and xanthine oxidation. In this study, it was shown that purified rat liver XO and xanthine dehydrogenase (XD) catalyse the NADH oxidation, generating O*- and inducing the peroxidation of liposomes, in a NADH and enzyme concentration-dependent manner. Comparatively to equimolar concentrations of xanthine, a higher peroxidation extent is observed in the presence of NADH. In addition, the peroxidation extent induced by XD is higher than that observed with XO. The in vivo-predominant dehydrogenase is, therefore, intrinsically efficient at generating ROS, without requiring the conversion to XO. Our results suggest that, in those pathological conditions where an increase on NADH concentration occurs, the NADH oxidation catalysed by XD may constitute an important pathway for ROS-mediated tissue injuries.

Aldehyde Oxidase↗
PubMed2006

Monoamine oxidase A rather than monoamine oxidase B inhibition increases nicotine reinforcement in rats.

Although nicotine is considered to be responsible for the addictive properties of tobacco, growing evidence underlines the importance of non-nicotine components in smoking reinforcement. It has been shown that tobacco smoke contains monoamine oxidase (MAO) A and B inhibitors and decreases MAO-A and MAO-B activity in smokers. Here, we investigated the effects of clorgyline hydrochloride (irreversible MAO-A inhibitor; 2 mg/kg/day), selegiline (irreversible MAO-B inhibitor; 4 mg/kg) and the beta-carboline norharmane hydrochloride (reversible MAO-B inhibitor; 5 mg/kg/day) treatments on nicotine self-administration (30 microg/kg/infusion, free base) in rats. Independent of the responsiveness to novelty and locomotor activity stimulation, only clorgyline hydrochloride treatment increased the intake of nicotine in a fixed-ratio schedule (FR5) of reinforcement. When a progressive-ratio schedule was implemented, both clorgyline hydrochloride and norharmane hydrochloride treatments potentiated the reinforcing effects of nicotine, whereas selegiline had no effect. Taken together, these results indicate that MAO-A inhibition interacts with nicotine to enhance its rewarding effects in rats and suggest that other compounds present in tobacco, such as beta-carboline, may also play an important role in sustaining smoking behavior in humans.

Analysis of Variance↗