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At least 271 records · Page 15Linked to original sources
PubMed1991

Pristanic acid does not accumulate in peroxisomal acyl-CoA oxidase deficiency: evidence for a distinct peroxisomal pristanyl-CoA oxidase.

The concentration of pristanic acid was measured in plasma from a patient with an isolated peroxisomal very long chain fatty acid (VLCFA) acyl-CoA oxidase deficiency, a defect in peroxisomal beta-oxidation resulting in accumulation of VLCFA in plasma and tissues. Although peroxisomes are believed to be involved in pristanic acid beta-oxidation, the pristanic acid level in the patient's plasma was within the control range. This finding provides evidence for the existence of a pristanyl-CoA oxidase distinct from the specific trihydroxycholestanoyl-CoA and VLCFA acyl-CoA oxidases.

Acyl-CoA Oxidase↗
PubMed1988

Immunocytochemical studies of cytochrome oxidase subunits in skeletal muscle of patients with partial cytochrome oxidase deficiencies.

Muscle biopsies from 17 patients with partial cytochrome oxidase deficiencies were investigated using immunocytochemical techniques for the localisation of cytochrome oxidase subunits. Antisera to subunits II/III (mitochondrially coded) and subunits IV, Vab, VIbc, VIIa, VIIbc and VIII (nuclear coded) showed clear particulate immunoreactivity in the muscle fibres of normal control biopsies. In the patients studied, muscle fibres with absent or decreased cytochrome oxidase activity also showed decreased immunoreactivity affecting all enzyme subunits. Particularly close correlation was seen between percentages of fibres showing absent enzyme activity and those showing decreased immunoreactivity for subunits II/III which are catalytic in function. The regulatory subunits IV-VIII were affected to varying degrees with different patterns of subunit loss occurring in individual muscle fibres.

Adolescent↗
PubMed1989

Identity of acyl-CoA oxidase with glutaryl-CoA oxidase.

Rats fed on clofibrate- and DEHP-containing diets showed virtually proportional increases in hepatic acyl-CoA oxidase and glutaryl-CoA oxidase activities. The solubilization profiles of the two activities from the light mitochondrial fraction of the liver homogenate of DEHP-treated rats were the same, and the glutaryl-CoA oxidase/acyl-CoA oxidase activity ratio remained constant through the purification. The final preparation obtained was a single protein based on the result of polyacrylamide gel electrophoresis. The evidence indicates that the two activities are associated with the same protein.

Acyl-CoA Oxidase↗
PubMed1991

Electron transfer reactions in the NADPH oxidase system of neutrophils--involvement of an NADPH-cytochrome c reductase in the oxidase system.

Membrane-bound NADPH oxidase of pig blood neutrophils was solubilized with heptylthioglucoside in a high yield. The solubilized preparation from myristate-stimulated cells (sample S) showed high O2- generating activity, and the preparation from resting cells (sample R) had no activity, but the two samples had equal amounts of flavins and cytochrome b-558 (cyt b-558). The electron transfer reactions to exogenous cytochrome c (cyt c) or cyt b-558 in samples S and R were examined. Under anaerobic conditions, NADPH-dependent cyt c reductase activity appeared higher in sample S than in sample R, and the addition of FMN and FAD greatly enhanced the reductase activity of sample S, but not that of sample R. No marked difference between the reductase activities of samples S and R was seen with NADH. Photoreduction of the NADPH oxidase system was examined in the absence of NADPH under anaerobic conditions by monitoring the reduction rates of exogenous cyt c using a flashlight with cut-off filters between 400 and 500 nm. Cyt c reduction was much higher in sample S than in sample R on photoexcitation at about 450 nm. Photoreduction was carried out with a band-pass filter for selective irradiation at 450 nm. Marked reduction of exogenous cyt c was observed only in sample S: the small reduction of cyt c by sample R was independent of the light wavelength and was equal to the blank level. In contrast, no difference in the reduction of cyt b-558 by the two samples was found by either NADPH or photoreduction. Under aerobic conditions, no direct reduction of either cyt c or cyt b-558 was observed. These results suggest that an NADPH-cyt c reductase (a membrane-bound flavoprotein) is involved in the NADPH oxidase system of stimulated neutrophils.

Anaerobiosis↗
PubMed1991

Inhibition of O2-. generating oxidase of neutrophils by iodonium biphenyl in a cell free system: effect of the redox state of the oxidase complex.

The conditions of inhibition of neutrophil O2-. generating oxidase by iodonium biphenyl (IBP) were studied. In a cell free system of oxidase activation consisting of neutrophil membranes and cytosol, GTP-gamma-S, Mg2+ and arachidonic acid, the inhibitory effect of IBP depended on the redox conditions of the medium. Inhibition was observed when the medium was supplemented with dithionite or NADPH. When the cell free system was incubated with IBP in the absence of reducing agents, full oxidase activity was recovered after removal of free IBP by gel filtration. Bovine neutrophil membranes, but not cytosol, contained component(s) sensitive to IBP. Upon treatment of neutrophil membranes by IBP followed by reduction, the spectrum of reduced cytochrome b558 was modified, suggesting that cytochrome b558 is a target site for IBP.

Animals↗
PubMed1996

Nitric oxide inhibits the cytochrome oxidase but not the alternative oxidase of plant mitochondria.

Oxygen consumption via the cytochrome pathway in isolated soybean (Glycine max [L.] Merr.) cotyledon mitochondria was inhibited by nitric oxide (NO) while respiration via the cyanide-insensitive alternative oxidase was not significantly affected. Inhibition of cytochrome pathway activity was rapidly reversible upon depletion of the added NO. NO production was also detected in solutions of NaNO2 plus ascorbate and the extent of cytochrome pathway inhibition was dependent on the NO2- concentration. Little inhibition of alternative pathway respiration was observed under similar conditions. The alternative oxidase may play a role in nitric oxide tolerance in higher plants and in organisms such as trypanosomes which contain a plant-like alternative oxidase.

Ascorbic Acid↗
PubMed2004

Nature of the oxomolybdenum-thiolate pi-bond: implications for Mo-S bonding in sulfite oxidase and xanthine oxidase.

The electronic structure of cis,trans-(L-N(2)S(2))MoO(X) (where L-N(2)S(2) = N,N'-dimethyl-N,N'-bis(2-mercaptophenyl)ethylenediamine and X = Cl, SCH(2)C(6)H(5), SC(6)H(4)-OCH(3), or SC(6)H(4)CF(3)) has been probed by electronic absorption, magnetic circular dichroism, and resonance Raman spectroscopies to determine the nature of oxomolybdenum-thiolate bonding in complexes possessing three equatorial sulfur ligands. One of the phenyl mercaptide sulfur donors of the tetradentate L-N(2)S(2) chelating ligand, denoted S(180), coordinates to molybdenum in the equatorial plane such that the OMo-S(180)-C(phenyl) dihedral angle is approximately 180 degrees, resulting in a highly covalent pi-bonding interaction between an S(180) p orbital and the molybdenum d(xy) orbital. This highly covalent bonding scheme is the origin of an intense low-energy S --> Mo d(xy) bonding-to-antibonding LMCT transition (E(max) approximately 16000 cm(-)(1), epsilon approximately 4000 M(-)(1) cm(-)(1)). Spectroscopically calibrated bonding calculations performed at the DFT level of theory reveal that S(180) contributes approximately 22% to the HOMO, which is predominantly a pi antibonding molecular orbital between Mo d(xy) and the S(180) p orbital oriented in the same plane. The second sulfur donor of the L-N(2)S(2) ligand is essentially nonbonding with Mo d(xy) due to an OMo-S-C(phenyl) dihedral angle of approximately 90 degrees. Because the formal Mo d(xy) orbital is the electroactive or redox orbital, these Mo d(xy)-S 3p interactions are important with respect to defining key covalency contributions to the reduction potential in monooxomolybdenum thiolates, including the one- and two-electron reduced forms of sulfite oxidase. Interestingly, the highly covalent Mo-S(180) pi bonding interaction observed in these complexes is analogous to the well-known Cu-S(Cys) pi bond in type 1 blue copper proteins, which display electronic absorption and resonance Raman spectra that are remarkably similar to these monooxomolybdenum thiolate complexes. Finally, the presence of a covalent Mo-S pi interaction oriented orthogonal to the MOO bond is discussed with respect to electron-transfer regeneration in sulfite oxidase and Mo=S(sulfido) bonding in xanthine oxidase.

Binding Sites↗
PubMed2006

Mechanism-based cofactor derivatization of a copper amine oxidase by a branched primary amine recruits the oxidase activity of the enzyme to turn inactivator into substrate.

The copper amine oxidases (CAOs) have evolved to catalyze oxidative deamination of unbranchedprimary amines to aldehydes. We report that a branched primary amine bearing an aromatization-prone moiety, ethyl 4-amino-4,5-dihydrothiophene-2-carboxylate (1), is recognized enantioselectively (S >> R) by bovine plasma amine oxidase (BPAO) both as a temporary inactivator and as a substrate. Substrate activity results from an O(2)-dependent turnover of the covalently modified enzyme, with release of 4-aminothiophene-2-carboxylate (2) as ultimate product. Interaction of (S)-1 with BPAO occurs within the enzyme active site with a dissociation constant of 0.76 microM. Evidence from kinetic and spectroscopic studies, and HPLC analysis of stoichiometric reactions of BPAO with (S)-1, combined with a model study using a quinone cofactor mimic, establishes that the enzyme metabolizes 1 according to a transamination mechanism. Following the initial isomerization of substrate Schiff base to product Schiff base, a facile aromatization of the latter results in a metastable N-aryl derivative of the reduced cofactor aminoresorcinol, which is catalytically inactive. The latter derivative is then slowly oxidized by O(2), apparently facilitated partially by the active-site Cu(II), to form a quinonimine of the native cofactor that releases 2 upon hydrolysis or transimination with substrate amine. Preferential metabolism of (S)-1 is consistent with the preferential removal of the pro-Salpha-proton in metabolism of benzylamine by BPAO. This study represents the first report of product identification in metabolism of a branched primary amine by a copper amine oxidase and suggests a novel type of reversible mechanism-based (covalent) inhibition where inhibition lifetime can be fine-tuned independently of inhibition potency.

Amine Oxidase (Copper-Containing)↗
PubMed1970

The regulation of xanthine oxidase. Inhibition by reduced nicotinamide-adenine dinucleotide of rat liver xanthine oxidase type D and of chick liver xanthine dehydrogenase.

1. Rat liver xanthine oxidase type D (NAD(+)-dependent) and chick liver xanthine oxidase are inhibited by NADH, which competes with NAD(+). 2. The addition of a NADH-reoxidizing system in the assay of these enzyme activities is proposed. 3. Rat liver xanthine oxidase type O (oxygen-dependent) is not affected by NADH.

Animals↗
PubMed2003

Properties of phagocyte NADPH oxidase p47-phox mutants with unmasked SH3 (Src homology 3) domains: full reconstitution of oxidase activity in a semi-recombinant cell-free system lacking arachidonic acid.

In an early step in the assembly of the phagocyte NADPH oxidase, p47-phox translocates from the cytosol to the membrane, mediated by engagement of the N-termini of two p47-phox Src homology 3 (SH3) domains with a proline-rich region (PRR) in the p22-phox subunit of cytochrome b (558). In response to phagocyte activation, several serine residues in a C-terminal arginine/lysine-rich domain of p47-phox are phosphorylated, leading to changes in the conformation of p47-phox and exposure of its N-terminal SH3 domain that is normally masked by internal association with the arginine/lysine-rich domain. We report that triple alanine substitutions at Asp-217, Glu-218 and Glu-223 in a short sequence that links the tandem p47-phox SH3 domains unmasked the N-terminal SH3 domain, similar to the effects of aspartic acid substitutions at Ser-310 and Ser-328 in the arginine/lysine-rich region. Recombinant p47-phox proteins with mutations in either the linker region or the arginine/lysine-rich domain were active in the absence of arachidonic acid stimulation in a cell-free NADPH oxidase system consisting of recombinant p67-phox, Rac1-guanosine 5'-[gamma-thio]triphosphate and neutrophil membranes. Supplementing neutrophil membranes with phosphoinositides or other negatively charged phospholipids markedly enhanced cell-free superoxide generation by these p47-phox mutants in the absence of arachidonic acid, to levels equivalent to those generated by wild-type p47-phox following arachidonic acid activation. This enhancement may be related to recruitment to the membrane of p47-phox mediated by a novel secondary phox homology (PX) domain binding site that broadly recognizes phospholipids. No specific enhancement by specific phosphorylated phosphatidylinositols was found to suggest a dominant role for the p47-phox primary PX domain binding site. Truncated p47-phox S310D S328D lacking the C-terminal PRR was inactive in the cell-free system without arachidonic acid, but was fully active with arachidonic acid. This suggests that activation of NADPH oxidase in an arachidonate-free cell-free system requires association of the p47-phox C-terminal PRR with the p67-phox C-terminal SH3 domain.

Amino Acid Sequence↗
PubMed2004

The role of the LRPPRC (leucine-rich pentatricopeptide repeat cassette) gene in cytochrome oxidase assembly: mutation causes lowered levels of COX (cytochrome c oxidase) I and COX III mRNA.

Leigh syndrome French Canadian (LSFC) is a variant of cytochrome oxidase deficiency found in Québec and caused by mutations in the LRPPRC (leucine-rich pentatricopeptide repeat cassette) gene. Northern blots showed that the LRPPRC mRNA levels seen in skeletal muscle>heart>placenta>kidney>liver>lung=brain were proportionally almost opposite in strength to the severity of the enzymic cytochrome oxidase defect. The levels of COX (cytochrome c oxidase) I and COX III mRNA visible on Northern blots were reduced in LSFC patients due to the common (A354V, Ala354-->Val) founder mutation. The amount of LRPPRC protein found in both fibroblast and liver mitochondria from LSFC patients was consistently reduced to <30% of control levels. Import of [(35)S]methionine LRPPRC into rat liver mitochondria was slower for the mutant (A354V) protein. A titre of LRPPRC protein was also found in nuclear fractions that could not be easily accounted for by mitochondrial contamination. [35S]Methionine labelling of mitochondrial translation products showed that the translation of COX I, and perhaps COX III, was specifically reduced in the presence of the mutation. These results suggest that the gene product of LRPPRC, like PET 309p, has a role in the translation or stability of the mRNA for mitochondrially encoded COX subunits. A more diffuse distribution of LRPPRC in LSFC cells compared with controls was evident when viewed by immunofluorescence microscopy, with less LRPPRC present in peripheral mitochondria.

Autopsy↗
PubMed1984

Quantitative transfer of the molybdenum cofactor from xanthine oxidase and from sulphite oxidase to the deficient enzyme of the nit-1 mutant of Neurospora crassa to yield active nitrate reductase.

An assay method is described for measurement of absolute concentrations of the molybdenum cofactor, based on complementation of the defective nitrate reductase ('apo nitrate reductase') in extracts of the nit-1 mutant of Neurospora crassa. A number of alternative methods are described for preparing, anaerobically, molybdenum-cofactor-containing solutions from sulphite oxidase, xanthine oxidase and desulpho xanthine oxidase. For assay, these were mixed with an excess of extract of the nit-1 mutant, incubated for 24 h at 3.5 degrees C then assayed for NADPH:nitrate reductase activity. In all cases, the specific activity of the molybdenum cofactor, expressed as mumol of NO2-formed/min per ng-atom of Mo added from the denatured molybdoenzyme , was 25 +/- 4, a value that agrees with the known catalytic activity of the nitrate reductase of wild-type Neurospora crassa. This indicates that, under our conditions, there was quantitative transfer of the molybdenum cofactor from denatured molybdoenzyme to yield fully active nitrate reductase. Comparable cofactor assay methods of previous workers, apparently indicating transfer efficiencies of at best a few per cent, have never excluded satisfactorily the possibility that cofactor activity arose, not from stoichiometric constituents of the molybdoenzymes , but from contaminants. The following factors were investigated separately in developing the assay:the efficiency of extraction of the cofactor from the original enzyme, the efficiency of the complementation reaction between cofactor and apo nitrate reductase, and the assay of the resultant nitrate reductase, which must be carried out under non-inhibitory conditions. Though the cofactor is unstable in air (t1/2 about 15 min at 3.5 degrees C), it is stable when kept anaerobic in the presence of sodium dithionite, in aqueous solution or in dimethyl sulphoxide (activity lost at the rate of about 3%/24 h at 20-25 degrees C). Studies of stabilities, and investigations of the effect of added molybdate on the assay, permit conclusions to be drawn about the ligation of molybdenum to the cofactor and about steps in incorporation of the cofactor into the apoenzyme. Though the development of nitrate reductase activity is slow at 3.5 degrees C (t1/2 1.5-3 h) the complementation reaction may be carried out in high yield, aerobically. This is ascribed to rapid formation of an air-stable but catalytically inactive complex of the cofactor, as a precursor of the active nitrate reductase.(ABSTRACT TRUNCATED AT 400 WORDS)

Apoenzymes↗
PubMed2005

Spermine oxidase SMO(PAOh1), Not N1-acetylpolyamine oxidase PAO, is the primary source of cytotoxic H2O2 in polyamine analogue-treated human breast cancer cell lines.

The induction of polyamine catabolism and its production of H2O2 have been implicated in the response to specific antitumor polyamine analogues. The original hypothesis was that analogue induction of the rate-limiting spermidine/spermine N1-acetyltransferase (SSAT) provided substrate for the peroxisomal acetylpolyamine oxidase (PAO), resulting in a decrease in polyamine pools through catabolism, oxidation, and excretion of acetylated polyamines and the production of toxic aldehydes and H2O2. However, the recent discovery of the inducible spermine oxidase SMO(PAOh1) suggested the possibility that the original hypothesis may be incomplete. To examine the role of the catabolic enzymes in the response of breast cancer cells to the polyamine analogue N1,N1-bis(ethyl)norspermine (BENSpm), a stable knockdown small interfering RNA strategy was used. BENSpm differentially induced SSAT and SMO(PAOh1) mRNA and activity in several breast cancer cell lines, whereas no N1-acetylpolyamine oxidase PAO mRNA or activity was detected. BENSpm treatment inhibited cell growth, decreased intracellular polyamine levels, and decreased ornithine decarboxylase activity in all cell lines examined. The stable knockdown of either SSAT or SMO(PAOh1) reduced the sensitivity of MDA-MB-231 cells to BENSpm, whereas double knockdown MDA-MB-231 cells were almost entirely resistant to the growth inhibitory effects of the analogue. Furthermore, the H2O2 produced through BENSpm-induced polyamine catabolism was found to be derived exclusively from SMO(PAOh1) activity and not through PAO activity on acetylated polyamines. These data suggested that SSAT and SMO(PAOh1) activities are the major mediators of the cellular response of breast tumor cells to BENSpm and that PAO plays little or no role in this response.

Acetyltransferases↗
PubMed1993

Cytosolic oxidase factors in the NADPH-dependent oxidase of human neutrophils.

The NADPH-dependent superoxide generating system of human PMNs is a complex, multicomponent system. Studies over the past two decades have identified some of the various components both in the membrane and in the cytosol. The cytosolic factors p47 phox and p67 phox are clearly essential components of the oxidase, as evidenced by their absence producing autosomal CGD. Despite this, the specific function of each of these factors in the assembled oxidase remains unknown. In the case of p47 phox, determinants for translocation are multifactorial, depending in part on phosphorylation and in part on the participation of a functional domain at p47 phox(323-332). The importance of SH3 regions and proline-rich domains in intramolecular interactions and associations with the membrane skeleton remain to be defined. In addition, factors which modulate the assembly of this oxidase are largely unknown and their elucidation may provide insights into novel means by which to modify the inflammatory response.

Amino Acid Sequence↗
PubMed1982

Site of aromatic L-amino acid oxidase in dead bovine spermatozoa and determination of between-bull differences in the percentage of dead spermatozoa by oxidase activity.

Most (94%) of the aromatic L-amino acid oxidase activity in dead bovine spermatozoa was recovered in tail preparations. The enzyme was released from the cell in sodium citrate but not in sodium phosphate or sodium chloride solutions but oxidase activity was not significantly different in sodium phosphate or sodium citrate buffers (9.6 microliters O2/h and 11.2 microliters O2/h). The activity in ejaculated spermatozoa was correlated with the percentage of dead spermatozoa (r = 0.954, P less than 0.01) but could not be detected in freshly collected epididymal spermatozoa. Killed epididymal spermatozoa showed oxidase activity (10.1 microliters O2/h) similar to that of killed ejaculated spermatozoa (9.2 microliters O2/h). It is concluded that death of spermatozoa occurs in the ampulla and/or at ejaculation and that between-bull differences in the percentage of dead spermatozoa are a consequence of differences between bulls in conditions in the ampulla and/or at ejaculation.

Amino Acid Oxidoreductases↗
PubMed1991

Induction of lung lysyl oxidase activity and lysyl oxidase protein by exposure of rats to cadmium chloride: properties of the induced enzyme.

Inspiration of CdCl2 results in a focally fibrotic response in rat lungs and markedly increases the activity of lung lysyl oxidase. Western blot analyses of urea-extractable rat lung proteins revealed that the levels of an immunoreactive, 32,000-Da protein were markedly increased in the cadmium-exposed rat lung tissue, consistent with the induction of lysyl oxidase protein. Anion exchange chromatography revealed low levels of multiple peaks of catalytically functional lysyl oxidase in control rat lung extracts, while the profile of cadmium-exposed rat lung extracts displayed markedly elevated levels of multiple peaks of enzyme activity indicating that the charge heterogeneity is expressed in the activated enzyme. The cadmium-induced enzyme was purified as a species of 32 kDa, without resolving individual ionic variants. The catalytic and physical properties of the isolated enzyme were very similar to those of previously well characterized basal enzyme of bovine aorta, including the presence of a pyrroloquinoline quinone-like carbonyl cofactor. The copper and cadmium content of the cadmium-induced enzyme indicated little if any replacement of tightly-bound copper by cadmium in the exposed lung.

Aminopropionitrile↗
PubMed2000

In vitro effects of corticosteroids, DDT, and 4, 9-dichlorodibenzodioxin on rat liver xanthine oxidase activity. Interactions between xanthine oxidase and cytochrome P450 in rat liver in vivo.

It was established that deoxycorticosterone, cortisol, dexamethasone, DDT, and 4,9-dichlorodibenzodioxin inhibit in vitro binding of xanthine to highly purified rat liver xanthine oxidase. They are suggested to be allosteric inhibitors. The corresponding inhibition and binding constants were estimated. Also established was that cortisol and DDT, in dose 20 mg per kg of weight, inhibit xanthine oxidase and increase microsomal cytochrome P450 level in rat liver. There is an inverse relationship between xanthine oxidase activity and cytochrome P450 level in rat liver.

Adrenal Cortex Hormones↗