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Zaman A, Khan S, Dutta B, Yakout SM, Ibrahim SS, Mir MH. Synthesis and characterization of a new 4-styrylpyridine based square planar copper(II) complex: exploration of phenoxazinone synthase-mimicking activity and DFT study. J COORD CHEM 2019. [DOI: 10.1080/00958972.2019.1651297] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Akhtaruz Zaman
- Department of Chemistry, Aliah University, Kolkata, India
| | - Samim Khan
- Department of Chemistry, Aliah University, Kolkata, India
| | - Basudeb Dutta
- Department of Chemistry, Aliah University, Kolkata, India
| | - Sobhy M. Yakout
- Biochemistry Department, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Shebl S. Ibrahim
- Biochemistry Department, College of Science, King Saud University, Riyadh, Saudi Arabia
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2
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Gaule TG, Smith MA, Tych KM, Pirrat P, Trinh CH, Pearson AR, Knowles PF, McPherson MJ. Oxygen Activation Switch in the Copper Amine Oxidase of Escherichia coli. Biochemistry 2018; 57:5301-5314. [PMID: 30110143 PMCID: PMC6136094 DOI: 10.1021/acs.biochem.8b00633] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Copper amine oxidases (CuAOs) are metalloenzymes that reduce molecular oxygen to hydrogen peroxide during catalytic turnover of primary amines. In addition to Cu2+ in the active site, two peripheral calcium sites, ∼32 Å from the active site, have roles in Escherichia coli amine oxidase (ECAO). The buried Ca2+ (Asp533, Leu534, Asp535, Asp678, and Ala679) is essential for full-length protein production, while the surface Ca2+ (Glu573, Tyr667, Asp670, and Glu672) modulates biogenesis of the 2,4,5-trihydroxyphenylalanine quinone (TPQ) cofactor. The E573Q mutation at the surface site prevents calcium binding and TPQ biogenesis. However, TPQ biogenesis can be restored by a suppressor mutation (I342F) in the proposed oxygen delivery channel to the active site. While supporting TPQ biogenesis (∼60% WTECAO TPQ), I342F/E573Q has almost no amine oxidase activity (∼4.6% WTECAO activity). To understand how these long-range mutations have major effects on TPQ biogenesis and catalysis, we employed ultraviolet-visible spectroscopy, steady-state kinetics, inhibition assays, and X-ray crystallography. We show that the surface metal site controls the equilibrium (disproportionation) of the Cu2+-substrate reduced TPQ (TPQAMQ) Cu+-TPQ semiquinone (TPQSQ) couple. Removal of the calcium ion from this site by chelation or mutagenesis shifts the equilibrium to Cu2+-TPQAMQ or destabilizes Cu+-TPQSQ. Crystal structure analysis shows that TPQ biogenesis is stalled at deprotonation in the Cu2+-tyrosinate state. Our findings support WTECAO using the inner sphere electron transfer mechanism for oxygen reduction during catalysis, and while a Cu+-tyrosyl radical intermediate is not essential for TPQ biogenesis, it is required for efficient biogenesis.
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Affiliation(s)
- Thembaninkosi G Gaule
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences , University of Leeds , Leeds LS2 9JT , U.K
| | - Mark A Smith
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences , University of Leeds , Leeds LS2 9JT , U.K
| | - Katarzyna M Tych
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences , University of Leeds , Leeds LS2 9JT , U.K.,Physik-Department, Lehrstuhl für Biophysik E22 , Technische Universität München , D-85748 Garching , Germany
| | - Pascale Pirrat
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences , University of Leeds , Leeds LS2 9JT , U.K
| | - Chi H Trinh
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences , University of Leeds , Leeds LS2 9JT , U.K
| | - Arwen R Pearson
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences , University of Leeds , Leeds LS2 9JT , U.K.,Hamburg Centre of Ultrafast Imaging and Institute for Nanostructure and Solid State Physics , Universität Hamburg , D-22761 Hamburg , Germany
| | - Peter F Knowles
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences , University of Leeds , Leeds LS2 9JT , U.K
| | - Michael J McPherson
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences , University of Leeds , Leeds LS2 9JT , U.K
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Primary Amine Oxidase of Escherichia coli Is a Metabolic Enzyme that Can Use a Human Leukocyte Molecule as a Substrate. PLoS One 2015; 10:e0142367. [PMID: 26556595 PMCID: PMC4640556 DOI: 10.1371/journal.pone.0142367] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 10/21/2015] [Indexed: 12/17/2022] Open
Abstract
Escherichia coli amine oxidase (ECAO), encoded by the tynA gene, catalyzes the oxidative deamination of aromatic amines into aldehydes through a well-established mechanism, but its exact biological role is unknown. We investigated the role of ECAO by screening environmental and human isolates for tynA and characterizing a tynA-deletion strain using microarray analysis and biochemical studies. The presence of tynA did not correlate with pathogenicity. In tynA+ Escherichia coli strains, ECAO enabled bacterial growth in phenylethylamine, and the resultant H2O2 was released into the growth medium. Some aminoglycoside antibiotics inhibited the enzymatic activity of ECAO, which could affect the growth of tynA+ bacteria. Our results suggest that tynA is a reserve gene used under stringent environmental conditions in which ECAO may, due to its production of H2O2, provide a growth advantage over other bacteria that are unable to manage high levels of this oxidant. In addition, ECAO, which resembles the human homolog hAOC3, is able to process an unknown substrate on human leukocytes.
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4
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Gaule TG, Smith MA, Pearson AR, Knowles PF, McPherson MJ. Probing the molecular mechanisms in copper amine oxidases by generating heterodimers. Chembiochem 2015; 16:559-64. [PMID: 25607656 PMCID: PMC4497604 DOI: 10.1002/cbic.201402653] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Indexed: 11/29/2022]
Abstract
For some homodimeric copper amine oxidases (CuAO), there is suggestive evidence of differential activity at the two active sites implying potential cooperativity between the two monomers. To examine this phenomenon for the Arthrobacter globiformis CuAO (AGAO), we purified a heterodimeric form of the enzyme for comparison with the homodimer. The heterodimer comprises an active wild-type monomer and an inactive monomer in which an active-site tyrosine is mutated to phenylalanine (Y382F). This mutation prevents the formation of the trihydroxyphenylalanine quinone (TPQ) cofactor. A pETDuet vector and a dual fusion tag strategy was used to purify heterodimers (WT/Y382F) from homodimers. Purity was confirmed by western blot and native PAGE analyses. Spectral and kinetic studies support the view that whether there are one or two functional monomers in the dimer, the properties of each functional monomer are the same, thus indicating no communication between the active sites in this bacterial enzyme.
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Affiliation(s)
- Thembaninkosi G Gaule
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of LeedsLS2 9JT Leeds (UK) E-mail:
| | - Mark A Smith
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of LeedsLS2 9JT Leeds (UK) E-mail:
| | - Arwen R Pearson
- Hamburg Centre of Ultrafast Imaging, University of Hamburg, CFELBuilding 99, Luruper Chausse 149, 22761 Hamburg (Germany)
| | - Peter F Knowles
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of LeedsLS2 9JT Leeds (UK) E-mail:
| | - Michael J McPherson
- Astbury Centre for Structural Molecular Biology, School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of LeedsLS2 9JT Leeds (UK) E-mail:
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5
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Solomon EI, Heppner DE, Johnston EM, Ginsbach JW, Cirera J, Qayyum M, Kieber-Emmons MT, Kjaergaard CH, Hadt RG, Tian L. Copper active sites in biology. Chem Rev 2014; 114:3659-853. [PMID: 24588098 PMCID: PMC4040215 DOI: 10.1021/cr400327t] [Citation(s) in RCA: 1147] [Impact Index Per Article: 114.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
| | - David E. Heppner
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | | | - Jake W. Ginsbach
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | - Jordi Cirera
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | - Munzarin Qayyum
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | | | | | - Ryan G. Hadt
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | - Li Tian
- Department of Chemistry, Stanford University, Stanford, CA, 94305
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6
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Finney J, Moon HJ, Ronnebaum T, Lantz M, Mure M. Human copper-dependent amine oxidases. Arch Biochem Biophys 2014; 546:19-32. [PMID: 24407025 DOI: 10.1016/j.abb.2013.12.022] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 12/24/2013] [Accepted: 12/26/2013] [Indexed: 12/11/2022]
Abstract
Copper amine oxidases (CAOs) are a class of enzymes that contain Cu(2+) and a tyrosine-derived quinone cofactor, catalyze the conversion of a primary amine functional group to an aldehyde, and generate hydrogen peroxide and ammonia as byproducts. These enzymes can be classified into two non-homologous families: 2,4,5-trihydroxyphenylalanine quinone (TPQ)-dependent CAOs and the lysine tyrosylquinone (LTQ)-dependent lysyl oxidase (LOX) family of proteins. In this review, we will focus on recent developments in the field of research concerning human CAOs and the LOX family of proteins. The aberrant expression of these enzymes is linked to inflammation, fibrosis, tumor metastasis/invasion and other diseases. Consequently, there is a critical need to understand the functions of these proteins at the molecular level, so that strategies targeting these enzymes can be developed to combat human diseases.
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Affiliation(s)
- Joel Finney
- Department of Chemistry, The University of Kansas, Lawrence, KS 66045, USA
| | - Hee-Jung Moon
- Department of Chemistry, The University of Kansas, Lawrence, KS 66045, USA
| | - Trey Ronnebaum
- Department of Chemistry, The University of Kansas, Lawrence, KS 66045, USA
| | - Mason Lantz
- Department of Chemistry, The University of Kansas, Lawrence, KS 66045, USA
| | - Minae Mure
- Department of Chemistry, The University of Kansas, Lawrence, KS 66045, USA.
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7
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Kurtis CRP, Knowles PF, Parsons MR, Gaule TG, Phillips SEV, McPherson MJ. Tyrosine 381 in E. coli copper amine oxidase influences substrate specificity. J Neural Transm (Vienna) 2011; 118:1043-53. [PMID: 21547391 DOI: 10.1007/s00702-011-0620-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Accepted: 02/22/2011] [Indexed: 11/28/2022]
Abstract
Copper amine oxidases are important for the metabolism of a range of biogenic amines. Here, we focus on substrate specificity in the E. coli copper amine oxidase (ECAO) and specifically the role of Tyr 381. This residue, and its equivalent, in other copper amine oxidases has been referred to as a "gating" residue able to move position depending upon the presence or absence of amine substrate. The position of this residue suggests a role in substrate selectivity. We have compared the properties of two variant forms of ECAO, Y381F and Y381A, with wild-type enzyme by steady-state kinetics of oxidation of a number of amine substrates, modes of inhibitor interactions and X-ray structure determination. Y381F displays a similar catalytic efficiency to wild type against the preferred substrate β-phenylethylamine. In both cases oxidation of the alternative aromatic amine substrate benzylamine is relatively poor, although Y381F represents an efficient benzylamine oxidase. By contrast, Y381A performed poorly against both aromatic substrates predominantly due to an increased K (M) which we propose is due to the lack of an aromatic residue to orient substrate towards the TPQ and active site base. These results are supported by different behaviour of Y381A to inhibition with 2-hydrazinopyridine. We also report on methylamine turnover by the three enzymes. We propose that Y381, together with another residue Y387, may be considered of critical importance for the substrate selectivity of ECAO, through stacking or hydrophobic interactions with substrate.
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Affiliation(s)
- Christian R P Kurtis
- Astbury Centre for Structural Molecular Biology, Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
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8
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Chen ZW, Datta S, Dubois JL, Klinman JP, Mathews FS. Mutation at a strictly conserved, active site tyrosine in the copper amine oxidase leads to uncontrolled oxygenase activity. Biochemistry 2010; 49:7393-402. [PMID: 20684524 DOI: 10.1021/bi100643y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The copper amine oxidases carry out two copper-dependent processes: production of their own redox-active cofactor (2,4,5-trihydroxyphenylalanine quinone, TPQ) and the subsequent oxidative deamination of substrate amines. Because the same active site pocket must facilitate both reactions, individual active site residues may serve multiple roles. We have examined the roles of a strictly conserved active site tyrosine Y305 in the copper amine oxidase from Hansenula polymorpha kinetically, spetroscopically (Dubois and Klinman (2006) Biochemistry 45, 3178), and, in the present work, structurally. While the Y305A enzyme is almost identical to the wild type, a novel, highly oxygenated species replaces TPQ in the Y305F active sites. This new structure not only provides the first direct detection of peroxy intermediates in cofactor biogenesis but also indicates the critical control of oxidation chemistry that can be conferred by a single active site residue.
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Affiliation(s)
- Zhi-Wei Chen
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 South Euclid Avenue, Box 8231, St. Louis, Missouri 63110, USA
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9
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Smith MA, Pirrat P, Pearson AR, Kurtis CRP, Trinh CH, Gaule TG, Knowles PF, Phillips SEV, McPherson MJ. Exploring the roles of the metal ions in Escherichia coli copper amine oxidase. Biochemistry 2010; 49:1268-80. [PMID: 20052994 PMCID: PMC2817917 DOI: 10.1021/bi901738k] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
To investigate the role of the active site copper in Escherichia coli copper amine oxidase (ECAO), we initiated a metal-substitution study. Copper reconstitution of ECAO (Cu-ECAO) restored only approximately 12% wild-type activity as measured by k(cat(amine)). Treatment with EDTA, to remove exogenous divalent metals, increased Cu-ECAO activity but reduced the activity of wild-type ECAO. Subsequent addition of calcium restored wild-type ECAO and further enhanced Cu-ECAO activities. Cobalt-reconstituted ECAO (Co-ECAO) showed lower but significant activity. These initial results are consistent with a direct electron transfer from TPQ to oxygen stabilized by the metal. If a Cu(I)-TPQ semiquinone mechanism operates, then an alternative outer-sphere electron transfer must also exist to account for the catalytic activity of Co-ECAO. The positive effect of calcium on ECAO activity led us to investigate the peripheral calcium binding sites of ECAO. Crystallographic analysis of wild-type ECAO structures, determined in the presence and absence of EDTA, confirmed that calcium is the normal ligand of these peripheral sites. The more solvent exposed calcium can be easily displaced by mono- and divalent cations with no effect on activity, whereas removal of the more buried calcium ion with EDTA resulted in a 60-90% reduction in ECAO activity and the presence of a lag phase, which could be overcome under oxygen saturation or by reoccupying the buried site with various divalent cations. Our studies indicate that binding of metal ions in the peripheral sites, while not essential, is important for maximal enzymatic activity in the mature enzyme.
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Affiliation(s)
- Mark A Smith
- Astbury Centre for Structural Molecular Biology and Institute of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
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10
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Houen G, Struve C, Søndergaard R, Friis T, Anthoni U, Nielsen PH, Christophersen C, Petersen BO, Duus JØ. Substrate specificity of the bovine serum amine oxidase and in situ characterisation of aminoaldehydes by NMR spectroscopy. Bioorg Med Chem 2005; 13:3783-96. [PMID: 15863005 DOI: 10.1016/j.bmc.2005.03.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2004] [Revised: 03/07/2005] [Accepted: 03/11/2005] [Indexed: 10/25/2022]
Abstract
The oxidation of spermidine or homospermidine with bovine serum amine oxidase (BSAO) was monitored in situ, using proton nuclear magnetic resonance spectroscopy in water with 10% D(2)O. NMR assignments were performed by spin decoupling and COSY spectra or by comparison with data from synthetic aminoaldehydes. The results represent the first in situ characterisation of the highly reactive aminoaldehydes and showed oxidation at the N(1) amino group of spermidine and homospermidine. Comparison of homospermidine with a variety of substrates revealed that among straight chain di- and polyamines both an aminopropyl group and two primary amino groups separated by seven (norspermidine) or eight (spermidine) carbon atoms were required for optimal substrate ability. However, highest activity was seen with the substrate N-(4-aminobutyl)hexahydropyrimidine, showing that the substrate channel of BSAO has a dual substrate preference, with moderately bulky substituents at the distal end of a diamine contributing equally well as an alkyl amino group. Cytotoxic investigations of a variety of substrates for BSAO, confirmed previous results, that cytotoxicity is primarily linked to polyamines encompassing the aminopropyl moiety. No acrolein was observed at any time during the oxidation showing that it reacts very fast with available amino groups forming a variety of derivatives.
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Affiliation(s)
- Gunnar Houen
- Department of Research and Development, Statens Serum Institute, Artillerivej 5, DK-2300 Copenhagen, Denmark.
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11
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Dubois JL, Klinman JP. Mechanism of post-translational quinone formation in copper amine oxidases and its relationship to the catalytic turnover. Arch Biochem Biophys 2005; 433:255-65. [PMID: 15581581 DOI: 10.1016/j.abb.2004.08.036] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2004] [Revised: 08/31/2004] [Indexed: 11/22/2022]
Abstract
Copper amine oxidases (CAOs) post-translationally construct a redox-active quinone from an amino acid side chain in their polypeptide chain. As such, these enzymes illustrate how nature is able to expand upon naturally-occurring side chains to create new, catalytically powerful functionalities. The active sites of the CAOs are highly unusual in their ability to catalyze two very different reactions: single-turnover, oxygen-dependent quinone formation, followed by catalytic oxidation (formally dehydrogenation) of amines. This review summarizes our current understanding of the pathway whereby the 2,4,5-trihydroxyphenylalanyl quinone (TPQ) cofactor is generated from the phenolic side chain of tyrosine. This reaction occurs spontaneously intermediates in the presence of O(2) and active site bound Cu(II), without the assistance of other proteins or cofactors. Ongoing work has focused on uncovering the details of the TPQ formation mechanism. A larger goal is to understand how a single active site is capable of supporting both quinone formation and subsequent catalytic turnover.
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Affiliation(s)
- Jennifer L Dubois
- Department of Chemistry, University of California at Berkeley, Berkeley, CA 94720, USA
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Pietrangeli P, Nocera S, Federico R, Mondovì B, Morpurgo L. Inactivation of copper-containing amine oxidases by turnover products. ACTA ACUST UNITED AC 2003; 271:146-52. [PMID: 14686927 DOI: 10.1046/j.1432-1033.2003.03913.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
For bovine serum amine oxidase, two different mechanisms of substrate-induced inactivation have been proposed. One consists of a slow oxidation by H2O2 of a conserved residue in the reduced enzyme after the fast turnover phase [Pietrangeli, P., Nocera, S., Fattibene, P., Wang, X.T., Mondovì, B. & Morpurgo, L. (2000) Biochem. Biophys. Res. Commun.267, 174-178] and the other of the oxidation by H2O2 of the dihydrobenzoxazole in equilibrium with the product Schiff base, during the catalytic cycle [Lee, Y., Shepard, E., Smith, J., Dooley, D.M. & Sayre, L.M. (2001) Biochemistry40, 822-829]. To discriminate between the two mechanisms, the inactivation was studied using Lathyrus cicera (red vetchling) amine oxidase. This, in contrast to bovine serum amine oxidase, formed the Cu+-semiquinolamine radical with a characteristic UV-vis spectrum when oxygen was exhausted by an excess of any tested amine in a closed cuvette. The inactivation, lasting about 90 min, was simultaneous with the radical decay and with the formation of a broad band (shoulder) at 350 nm. No inactivation occurred when a thousand-fold excess of amine was rapidly oxidized in an L. cicera amine oxidase solution stirred in open air. Thus, the inactivation is a slow reaction of the reduced enzyme with H2O2, following the turnover phase. Catalase protected L. cicera amine oxidase from inactivation. This effect was substrate-dependent, varying from full protection (benzylamine) to no protection (putrescine). In the absence of H2O2, a specific inactivating reaction, without formation of the 350 nm band, was induced by some aldehydes, notably putrescine. Some mechanisms of inactivation are proposed.
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Affiliation(s)
- Paola Pietrangeli
- Department of Biochemical Sciences A. Rossi Fanelli and C.N.R. Institute of Molecular Biology and Pathology, University of Rome La Sapienza, Rome, Italy.
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13
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Pietrangeli P, Nocera S, Mondovi B, Morpurgo L. Is the catalytic mechanism of bacteria, plant, and mammal copper-TPQ amine oxidases identical? BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1647:152-6. [PMID: 12686125 DOI: 10.1016/s1570-9639(03)00083-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
This short review is mostly concerned with the work carried out in Rome on the copper amine oxidase from bovine serum (BSAO). The first target was the copper oxidation state and its relationship with the organic cofactor. It was found that copper is not reduced on reaction with amines under anaerobic conditions or along the catalytic cycle and that it is not within bonding distance of the quinone cofactor. The copper stability in the oxidised state was supported by BSAO ability to oxidise benzylhydrazine, a slow substrate, in the presence of N,N-diethyldithiocarbamate (DDC) and by the substantial catalytic activity of Co(2+)-substituted BSAO. Parallel work established that only one subunit of the dimeric enzyme readily binds reagents of the carbonyl group. Flexible hydrazides with a long aromatic tail were found to be highly specific inhibitors, suggesting the presence of an extended hydrophobic region at the catalytic site. A study by stopped-flow transient spectroscopy and steady state kinetics led to the formulation of a simplified, yet complete and consistent, catalytic mechanism for BSAO that was compared with that available for lentil seedling amine oxidase (LSAO). As in other copper amine oxidases, BSAO is inactivated by H(2)O(2) produced in the catalytic reaction, while the cofactor is stabilised in its reduced state. A conserved tyrosine hydrogen-bonded to the cofactor might be oxidised.
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Affiliation(s)
- P Pietrangeli
- Department of Biochemical Sciences A. Rossi Fanelli and C.N.R. Centre of Molecular Biology, La Sapienza, University, P.le A. Moro 5, 00185 Rome, Italy
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14
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Saysell CG, Tambyrajah WS, Murray JM, Wilmot CM, Phillips SEV, McPherson MJ, Knowles PF. Probing the catalytic mechanism of Escherichia coli amine oxidase using mutational variants and a reversible inhibitor as a substrate analogue. Biochem J 2002; 365:809-16. [PMID: 11985492 PMCID: PMC1222726 DOI: 10.1042/bj20011435] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2001] [Revised: 03/01/2002] [Accepted: 05/02/2002] [Indexed: 11/17/2022]
Abstract
Copper amine oxidases are homodimeric enzymes containing one Cu(2+) ion and one 2,4,5-trihydroxyphenylalanine quinone (TPQ) per monomer. Previous studies with the copper amine oxidase from Escherichia coli (ECAO) have elucidated the structure of the active site and established the importance in catalysis of an active-site base, Asp-383. To explore the early interactions of substrate with enzyme, we have used tranylcypromine (TCP), a fully reversible competitive inhibitor, with wild-type ECAO and with the active-site base variants D383E and D383N. The formation of an adduct, analogous to the substrate Schiff base, between TCP and the TPQ cofactor in the active site of wild-type ECAO and in the D383E and D383N variants has been investigated over the pH range 5.5-9.4. For the wild-type enzyme, the plot of the binding constant for adduct formation (K(b)) against pH is bell-shaped, indicating two pK(a)s of 5.8 and approximately 8, consistent with the preferred reaction partners being the unprotonated active-site base and the protonated TCP. For the D383N variant, the reaction pathway involving unprotonated base and protonated TCP cannot occur, and binding must follow a less favoured pathway with unprotonated TCP as reactant. Surprisingly, for the D383E variant, the K(b) versus pH behaviour is qualitatively similar to that of D383N, supporting a reaction pathway involving unprotonated TCP. The TCP binding data are consistent with substrate binding data for the wild type and the D383E variant using steady-state kinetics. The results provide strong support for a protonated amine being the preferred substrate for the wild-type enzyme, and emphasize the importance of the active-site base, Asp-383, in the primary binding event.
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Affiliation(s)
- Colin G Saysell
- Astbury Centre for Structural Molecular Biology, School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, U.K
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