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At least 289 records · Page 16Linked to original sources
PubMed1994

Light microscopic visualization of semicarbazide-sensitive amine oxidase (benzylamine oxidase) using a cerium method.

Light microscopic histochemical studies to visualize semicarbazide-sensitive and H2O2-generating amine oxidase (SSAOX, benzylamine oxidase, BAOX; EC 1.4.3.6?) are usually performed with the coupled peroxidatic oxidation technique of Ryder et al. [25]. For methodological reasons this procedure has its limitations and was therefore replaced by a more reliable and easier to perform cerium-DAB-H2O2-Co technique. With this method SSAOX was studied in many organs of various laboratory rodents and marmosets and in human placenta. Independent of the species the enzyme was present mostly in the plasma membrane of nearly all vascular and non-vascular smooth muscle cells. However, there was a species-dependence of SSOX activity; the highest amounts of stain were found in gerbils and marmosets. In addition, the enzyme was found in these two species in the capillary endothelium of some extra-nervous tissues. The plasma membrane localization of SSAOX and plasma membrane-associated H2O2 production suggest a functional role for the enzyme different from that of other amine oxidases which appear to be primarily involved in intracellular amine detoxification or degradation.

Animals↗
PubMed1993

Monoamine oxidase-A inhibitors and dopamine metabolism in rat caudatus: evidence that an increased cytosolic level of dopamine displaces reversible monoamine oxidase-A inhibitors in vivo.

The effects of reversible inhibitors of monoamine oxidase-A (moclobemide, Ro 41-1049, both 20 mg/kg, i.p., and brofaromine, 10 mg/kg, i.p.) on the outflow of dopamine (DA) and its metabolites (3,4-dihydroxyphenylacetic acid and homovanillic acid) as well as of 5-hydroxyindoleacetic acid was investigated by trans-striatal microdialysis in rats. These drugs markedly increased the level of DA in the dialysis fluid by 100% of basal values and concomitantly reduced the output of 3,4-dihydroxy-phenylacetic acid and homovanillic acid by 90%. The presence of tetrodotoxin in the perfusion fluid decreased the basal DA outflow and virtually abolished the rise in DA efflux after moclobemide administration. On the other hand, tetrodotoxin did not counteract the DA outflow induced by Ro 4-1284 (1 mg/kg, i.p.), a tetrabenazine derivative which rapidly releases DA from vesicles and causes a massive increase in the concentration of extravesicular amine. The injection of Ro 4-1284 30 min after moclobemide, brofaromine or Ro 41-1049 induced a 6-fold increase in DA outflow, which was accompanied by a transient increase in 3,4-dihydroxyphenylacetic acid levels. This latter effect was more marked for moclobemide than for the other two reversible inhibitors tested and was not observed in rats given the irreversible inhibitor clorgyline (5 mg/kg, i.p.). These results support the view that a large increase in the concentration of endogenous substrates in the cytosol might displace reversible monoamine oxidase-A inhibitors from the enzyme active sites. Therefore, the microdialysis technique seems to be a reliable in vivo method for assessing the degree of reversibility of monoamine oxidase inhibitors.

2H-Benzo(a)quinolizin-2-ol, 2-Ethyl-1,3,4,6,7,11b-↗
PubMed1998

Studies on the behaviour of semicarbazide-sensitive amine oxidase in Sprague-Dawley rats treated with the monoamine oxidase inhibitor tranylcypromine.

The possibility that increased levels of the activity of the semicarbazide-sensitive amine oxidase (SSAO) might, to some extent, compensate for the loss of monoamine oxidase (MAO) activity in the atypical form of Norrie Disease, was examined using the rat as a model. Long-term treatment with the MAO inhibitor tranylcypromine (1 mg/kg/day) resulted in sustained inhibition of MAO-A and MAO-B activities in liver and brain. After one week, the SSAO activity in heart had increased by 79% above the control levels. This increase was maintained for 3 weeks. Since such alterations might result from enzyme induction, the turnover of the enzyme was studied in cultured cells from rat aortic smooth muscle. The time-course of recovery of enzyme activity following irreversible inhibition by MDL 72145 corresponded to a half-life of approximately 6 days for this process.

Allylamine↗
PubMed1979

A coupled peroxidatic oxidation technique for the histochemical localization of monoamine oxidase A and B and benzylamine oxidase.

A coupled peroxidatic oxidation technique is presented which employs benzylamine and tyramine as substrates and clorgyline, deprenyl, phenelzine and pargyline as specific inhibitors. Using this technique with frozen sections of human term placenta and rat liver, the histochemical localization of monocamine oxidase A and B and bnezylamine oxidase has been demonstrated.

Animals↗
PubMed2002

Inhibition of monoamine oxidase modulates the behaviour of semicarbazide-sensitive amine oxidase (SSAO).

The specific activity and kinetic behaviour of semicarbazide-sensitive amine oxidase (EC 1.4.3.6; SSAO) towards benzylamine, in the rat heart, is affected by in vivo treatment with the non-selective monoamine oxidase (MAO) inhibitor tranylcypromine, but not by the selective MAO-A and -B inhibitors, clorgyline and lazabemide. SSAO activity was increased to 178% of control activity after 7 days of treatment with tranylcypromine. This increase appears to represent an increase in the limiting velocity (V(max)) for benzylamine oxidation with no significant change in the K(m) at that time-point. However, the K(m) for benzylamine oxidation was found to decrease in both controls and treated groups, in a time-dependent manner, during the treatment regime. These findings suggest a link between SSAO and cellular stress and may have importance in the context of the recent finding that tissue-SSAO is identical to a vascular adhesion protein (VAP1), involved in the process of inflammation.

Amine Oxidase (Copper-Containing)↗
PubMed1982

Characteristics and specificity of phenelzine and benserazide as inhibitors of benzylamine oxidase and monoamine oxidase.

The selectivity of benserazide and phenelzine toward inhibition of benzylamine oxidase (BzAO) and monoamine oxidases (MAO-A and MAO-B) was studied in homogenates of rat skull and lung. In addition, the kinetic interaction and reversibility of BzAO inhibition were assessed. Both drugs inhibited BzAO but only phenelzine inhibited MAO, whether tested in vitro or in vivo. Neither compound acted as an irreversible inhibitor of BzAO. Benserazide was found to be a noncompetitive inhibitor. Phenelzine acted as a substrate for BzAO followed by product-induced noncompetitive inhibition which was labile at 37 degrees but not at 4 degrees. A reversible component in phenelzine-induced inhibition of MAO-A and -B is also suggested from in vivo studies.

Animals↗
PubMed1985

Pyridoxamine as inhibitor of the blood plasma benzylamine oxidase and other copper-containing amine oxidases.

Pyridoxamine inhibits rabbit and pig plasma benzylamine oxidase (BAO), the diamine oxidase of pig kidney and the lysyloxidase of pig aorta in-vitro. In-vivo in the rabbit, the inhibitory activity of pyridoxamine on plasma BAO is antagonized by an increase in the level of this enzyme that is dependent on an increase in rate of synthesis, there being no variation in the degradation rate constant.

Animals↗
PubMed1995

Further studies on the ex-vivo effects of procarbazine and monomethylhydrazine on rat semicarbazide-sensitive amine oxidase and monoamine oxidase activities.

Following administration of the anticancer agent, procarbazine, or one of its metabolites, monomethylhydrazine, to rats, activities of monoamine oxidases A and B (MAO A and MAO B) and of semicarbazide-sensitive amine oxidase (SSAO) were measured ex-vivo. Both compounds were found to be potent inhibitors of SSAO in tissue homogenates, exhibiting ID50 values in most tissues of approximately 8 mg kg-1 (procarbazine) and 0.08 mg kg-1 (monomethylhydrazine). Concurrent dose-dependent inhibition of MAO activities did not occur. However, in liver, potentiation of MAO B activity, to 140% of that in controls, was apparent following monomethyl-hydrazine and this effect was independent of the drug dose. Both compounds produced a dose-dependent potentiation of MAO A in brown adipose tissue, the elevation being more pronounced following monomethylhydrazine, with activity rising to 350% of that in control homogenates. In a parallel in-vitro study, monomethylhydrazine was without effect on MAO A in brown adipose tissue homogenates. By perfusing the SSAO substrate, benzylamine, through the isolated mesenteric arterial bed of the rat, it was found that pretreatment of animals with procarbazine or monomethylhydrazine reduced metabolism of this amine by a similar degree as had been determined ex-vivo in blood vessel homogenates. The results presented suggest that these compounds would be suitable for use as selective inhibitors in pharmacological examinations of SSAO function in isolated tissues and organs.

Amine Oxidase (Copper-Containing)↗
PubMed1999

Monitoring catalytic reaction of bilirubin oxidase and determination of bilirubin and bilirubin oxidase activity by capillary electrophoresis.

Micellar electrokinetic chromatography (MEKC) has been exploited as an analytical method for the separation as well as for the determination of serum bilirubin fractions (alpha-, beta-, gamma- and delta-fraction), the activity of bilirubin oxidase (BOD), and for monitoring the catalytic reaction of BOD. The samples were followed by detection at 450 nm. The average limit of detection was in the 5.0 microM concentration range. The relative standard deviation (RSD) of migration times and peak area of bilirubin was less than 0.25% and 3.0%, respectively. This allowed us complete separation of the four bilirubin fractions (alpha-, beta-, gamma- and delta-fraction) and monitoring of the oxidation progress and the assay of the activity of bilirubin oxidase. The MEKC method is a convenient technique for studying the catalytic reaction of bilirubin oxidase at different pH and assaying the relationship between the four bilirubin fractions and diseases.

Bilirubin↗
PubMed1987

Nuclear functions required for cytochrome c oxidase biogenesis in Saccharomyces cerevisiae: multiple trans-acting nuclear genes exert specific effects on expression of each of the cytochrome c oxidase subunits encoded on mitochondrial DNA.

Fourteen nuclear complementation groups of mutants that specifically affect the three mitochondrially-encoded subunits of yeast cytochrome c oxidase have been characterized. Genes represented by these complementation groups are not required for mitochondrial transcription, transcript processing, or translation per se but are required for the expression of one of the three genes--COX1, COX2, or COX3--which encode the cytochrome c oxicase subunits I, II, or III, respectively. Five of these genes affect the biogenesis of cytochrome c oxidase subunit I, 3 affect the biogenesis of subunit II, 3 affect the biogenesis of subunit III and 3 affect the biogenesis of both cytochrome c oxidase subunit I and cytochrome b, the product of COB. Among the 5 complementation groups of mutants that affect the expression of COX1, 2 lack COX1 transcripts, 1 produces incompletely processed COX1 transcripts, and 2 contain normal levels of normal-sized COX1 transcripts. In contrast, all 3 complementation groups which affect the expression of COX2 and all 3 complementation groups which affect the expression of COX3 exhibit no, or little, detectable difference with respect to the wild type pattern of transcripts. The 3 complementation groups which affect the expression of both COX1 and COB all have aberrant COX1 and COB transcript patterns. These findings indicate that multiple trans-acting nuclear genes are required for specific expression of each COX gene encoded on mitochondrial DNA and suggest that their products act at different steps in the expression of these mitochondrial genes.

Cell Nucleus↗
PubMed1985

Luminometric determination of oxidase activity in peroxisomal fractions of rat liver: glycolate oxidase.

The feasibility of using the H2O2-mediated chemiluminescence for determination of the activity of oxidases in peroxisomes of rat liver has been investigated. In an assay medium containing luminol, horseradish peroxidase, and azide with glycolate as substrate, a linear relationship is obtained between the amount of peroxisomal protein used and the luminescence signal. In comparison with other techniques available for measuring the activities of peroxisomal oxidases the luminometric approach described here is 5-10 times more sensitive than the spectrophotometric methods and 100 times more efficient than the polarographic determination of O2. Under the optimal assay conditions the glycolate oxidase activity can be determined in amounts as low as 0.5 micrograms peroxisomal protein.

Alcohol Oxidoreductases↗
PubMed1983

Sequence homology of bacterial and mitochondrial cytochrome c oxidases. Partial sequence data of cytochrome c oxidase from Paracoccus denitrificans.

The aerobic electron transport chain of Paracoccus denitrificans is very similar to that of mitochondria. It has therefore been suggested that this bacterium might be evolutionarily related to mitochondria. The two subunits (Mr 45.000 and 28.000) of the Paracoccus cytochrome c oxidase were isolated and partially sequenced. The sequences were found to be surprisingly homologous to sequences of the subunits I and II of mitochondrial cytochrome c oxidases. The data provide a molecular basis for the symbiotic origin of mitochondria and strongly support the notion that in eucaryotic oxidases subunits I and/or II carry the redox centers, heme and copper.

Amino Acid Sequence↗
PubMed1992

The formate complex of the cytochrome bo quinol oxidase of Escherichia coli exhibits a 'g = 12' EPR feature analogous to that of 'slow' cytochrome oxidase.

The cytochrome bo quinol oxidase of Escherichia coli is homologous in sequence and in structure to cytochrome aa3 type cytochrome oxidase in subunit I, which contains the catalytic core. The cytochrome bo enzyme forms a formate complex which exhibits 'g = 12' and 'g = 2.9' EPR signals at X band; similar signals have previously been observed only in association with the 'slow' and formate-ligand states of cytochrome oxidase. These signals arise from transitions within integral spin multiples identified with the homologous heme-copper binuclear catalytic centers in both enzymes.

Bacterial Proteins↗
PubMed1998

A cooperative model for protonmotive heme-copper oxidases. The role of heme a in the proton pump of cytochrome c oxidase.

Oxido-reductions of metal centers in cytochrome c oxidase are linked to pK shifts of acidic groups in the enzyme (redox Bohr effects). The linkage at heme a results in proton uptake from the inner space upon reduction and proton release in the external space upon oxidation of the metal. The relationship of this process to the features of the proton pump in cytochrome c oxidase and its atomic structure revealed by X-ray crystallography to 2.8-2.3 A resolution is examined. A mechanism for the proton pump of cytochrome c oxidase, based on cooperative coupling at heme a, is proposed.

Amino Acid Sequence↗
PubMed1997

Molecular basis of sulfite oxidase deficiency from the structure of sulfite oxidase.

The molybdenum-containing enzyme sulfite oxidase catalyzes the conversion of sulfite to sulfate, the terminal step in the oxidative degradation of cysteine and methionine. Deficiency of this enzyme in humans usually leads to major neurological abnormalities and early death. The crystal structure of chicken liver sulfite oxidase at 1.9 A resolution reveals that each monomer of the dimeric enzyme consists of three domains. At the active site, the Mo is penta-coordinated by three sulfur ligands, one oxo group, and one water/hydroxo. A sulfate molecule adjacent to the Mo identifies the substrate binding pocket. Four variants associated with sulfite oxidase deficiency have been identified: two mutations are near the sulfate binding site, while the other mutations occur within the domain mediating dimerization.

Amino Acid Sequence↗
PubMed2001

Taenia crassiceps metacestodes have cytochrome oxidase aa3 but not cytochrome o functioning as terminal oxidase.

In mitochondria obtained from Taenia crassiceps metacestodes, carbon monoxide difference spectra reveal signals characteristic of the classical mitochondrial oxidase, cytochrome aa3, as well as signals suggesting the presence of 'cytochrome o'. In the present work, using photodissociation spectrophotometry and analysis of the haem groups, we conclude that there is no haem O in these larvae, and that the only cytochrome that functions as terminal oxidase is cytochrome c oxidase, aa3. At temperatures between -70 and -100 degrees C, the energy of activation for CO reassociation with cytochrome a3 was 10.5 kcal x mol(-1), and for oxygen binding 7.8 kcal x mol(-1).

Animals↗
PubMed1997

The cioAB genes from Pseudomonas aeruginosa code for a novel cyanide-insensitive terminal oxidase related to the cytochrome bd quinol oxidases.

The structural genes for the cyanide-insensitive terminal oxidase (CIO) of Pseudomonas aeruginosa were sequenced. The locus comprised two open reading frames, cioA and cioB, coding for gene products of 488 and 335 amino acid residues with predicted molecular masses of 54241 and 37016 Da respectively. These genes were encoded by a 2.7 kb transcript and probably comprise an operon. Upstream of a major transcriptional start site is a -10 promoter region and, approximately at nucleotides -50 and +13, there are sequences homologous to the binding site of the transcriptional regulator Anr. The deduced amino acid sequences of CioA and CioB are homologous to the cytochrome bd quinol oxidases of Escherichia coli and Azotobacter vinelandii. However, no cytochrome d-like signals were found in wild-type P. aeruginosa strains. An atypical cytochrome d-like signal was seen under low-aeration growth conditions but only in strains in which the cioAB genes were present on a high-copy-number plasmid. The appearance of these cytochrome d-like signals was not paralleled by a concomitant increase in CIO activity. These data support the hypothesis that the CIO of P. aeruginosa does not contain haem d. This raises the possibility that there is a family of bacterial quinol oxidases related to the cytochrome bd of E. coli that can differ in their haem composition from the E. coli paradigm.

Amino Acid Sequence↗
PubMed1996

Glyoxal oxidase from Phanerochaete chrysosporium is a new radical-copper oxidase.

A free radical-coupled copper complex has been identified as the catalytic structure in the active site of glyoxal oxidase from Phanerochaete chrysosporium based on a combination of spectroscopic and biochemical studies. The native (inactive) enzyme is activated by oxidants leading to the elimination of the cupric EPR signal consistent with formation of an antiferromagnetically coupled radical-copper complex. Oxidation also leads to the appearance of a substoichiometric free radical EPR signal with an average g value (gav = 2.0055) characteristic of phenoxyl tau-radicals arising from a minority apoenzyme fraction. Optical absorption, CD, and spectroelectrochemical measurements on the active enzyme reveal complex spectra extending into the near IR and define the redox potential for radical formation (E 1/2 = 0.64 V versus NHE, pH 7.0). Resonance Raman spectra have identified the signature of a modified (cysteinyl-tyrosine) phenoxyl in the vibrational spectra of the active complex. This radical-copper motif has previously been found only in galactose oxidase, with which glyoxal oxidase shares many properties despite lacking obvious sequence identity, and catalyzing a distinct reaction. The enzymes thus represent members of a growing class of free radical metalloenzymes based on the radical-copper catalytic motif and appear to represent functional variants that have evolved to distinct catalytic roles.

Alcohol Oxidoreductases↗