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Murakawa T, Kurihara K, Adachi M, Kusaka K, Tanizawa K, Okajima T. Re-evaluation of protein neutron crystallography with and without X-ray/neutron joint refinement. IUCRJ 2022; 9:342-348. [PMID: 35546796 PMCID: PMC9067118 DOI: 10.1107/s2052252522003657] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 04/01/2022] [Indexed: 06/15/2023]
Abstract
Protein neutron crystallography is a powerful technique to determine the positions of H atoms, providing crucial biochemical information such as the protonation states of catalytic groups and the geometry of hydrogen bonds. Recently, the crystal structure of a bacterial copper amine oxidase was determined by joint refinement using X-ray and neutron diffraction data sets at resolutions of 1.14 and 1.72 Å, respectively [Murakawa et al. (2020 ▸). Proc. Natl Acad. Sci. USA, 117, 10818-10824]. While joint refinement is effective for the determination of the accurate positions of heavy atoms on the basis of the electron density, the structural information on light atoms (hydrogen and deuterium) derived from the neutron diffraction data might be affected by the X-ray data. To unravel the information included in the neutron diffraction data, the structure determination was conducted again using only the neutron diffraction data at 1.72 Å resolution and the results were compared with those obtained in the previous study. Most H and D atoms were identified at essentially the same positions in both the neutron-only and the X-ray/neutron joint refinements. Nevertheless, neutron-only refinement was found to be less effective than joint refinement in providing very accurate heavy-atom coordinates that lead to significant improvement of the neutron scattering length density map, especially for the active-site cofactor. Consequently, it was confirmed that X-ray/neutron joint refinement is crucial for determination of the real chemical structure of the catalytic site of the enzyme.
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Affiliation(s)
- Takeshi Murakawa
- Department of Biochemistry, Faculty of Medicine, Osaka Medical and Pharmaceutical University, 2-7 Daigakumachi, Takatsuki, Osaka 569-8686, Japan
| | - Kazuo Kurihara
- Institute for Quantum Life Science, Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology, 2-4 Shirakata, Tokai, Ibaraki 319-1106, Japan
| | - Motoyasu Adachi
- Institute for Quantum Life Science, Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology, 2-4 Shirakata, Tokai, Ibaraki 319-1106, Japan
| | - Katsuhiro Kusaka
- Frontier Research Center for Applied Atomic Sciences, Ibaraki University, 162-1 Shirakata, Tokai, Ibaraki 319-1106, Japan
| | - Katsuyuki Tanizawa
- Institute of Scientific and Industrial Research (SANKEN), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
| | - Toshihide Okajima
- Institute of Scientific and Industrial Research (SANKEN), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
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2
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Shoji M, Murakawa T, Nakanishi S, Boero M, Shigeta Y, Hayashi H, Okajima T. Molecular mechanism of a large conformational change of the quinone cofactor in the semiquinone intermediate of bacterial copper amine oxidase. Chem Sci 2022; 13:10923-10938. [PMID: 36320691 PMCID: PMC9491219 DOI: 10.1039/d2sc01356h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 08/16/2022] [Indexed: 11/21/2022] Open
Abstract
Copper amine oxidase from Arthrobacter globiformis (AGAO) catalyses the oxidative deamination of primary amines via a large conformational change of a topaquinone (TPQ) cofactor during the semiquinone formation step. This conformational change of TPQ occurs in the presence of strong hydrogen bonds and neighboring bulky amino acids, especially the conserved Asn381, which restricts TPQ conformational changes over the catalytic cycle. Whether such a semiquinone intermediate is catalytically active or inert has been a matter of debate in copper amine oxidases. Here, we show that the reaction rate of the Asn381Ala mutant decreases 160-fold, and the X-ray crystal structures of the mutant reveals a TPQ-flipped conformation in both the oxidized and reduced states, preceding semiquinone formation. Our hybrid quantum mechanics/molecular mechanics (QM/MM) simulations show that the TPQ conformational change is realized through the sequential steps of the TPQ ring-rotation and slide. We determine that the bulky side chain of Asn381 hinders the undesired TPQ ring-rotation in the oxidized form, favoring the TPQ ring-rotation in reduced TPQ by a further stabilization leading to the TPQ semiquinone form. The acquired conformational flexibility of TPQ semiquinone promotes a high reactivity of Cu(i) to O2, suggesting that the semiquinone form is catalytically active for the subsequent oxidative half-reaction in AGAO. The ingenious molecular mechanism exerted by TPQ to achieve the “state-specific” reaction sheds new light on a drastic environmental transformation around the catalytic center. The large conformational change of topaquinone in bacterial copper amine oxidase occurs through the TPQ ring rotation and slide, which are essential to stabilize the semiquinone form.![]()
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Affiliation(s)
- Mitsuo Shoji
- Center for Computational Sciences, University of Tsukuba 1-1-1 Tennodai Tsukuba 305-8577 Ibaraki Japan
- JST-PRESTO 4-1-8 Honcho Kawaguchi 332-0012 Saitama Japan
| | - Takeshi Murakawa
- Department of Biochemistry, Osaka Medical and Pharmaceutical University 2-7 Daigakumachi Takatsuki 569-8686 Osaka Japan
| | - Shota Nakanishi
- Institute of Scientific and Industrial Research, Osaka University 8-1 Mihogaoka Ibaraki 567-0047 Osaka Japan
| | - Mauro Boero
- University of Strasbourg, Institut de Physique et Chimie des Matériaux de Strasbourg, CNRS, UMR 7504 23 rue du Loess F-67034 France
| | - Yasuteru Shigeta
- Center for Computational Sciences, University of Tsukuba 1-1-1 Tennodai Tsukuba 305-8577 Ibaraki Japan
| | - Hideyuki Hayashi
- Department of Chemistry, Osaka Medical and Pharmaceutical University 2-7 Daigakumachi Takatsuki 569-8686 Osaka Japan
| | - Toshihide Okajima
- Institute of Scientific and Industrial Research, Osaka University 8-1 Mihogaoka Ibaraki 567-0047 Osaka Japan
- Department of Chemistry, Osaka Medical and Pharmaceutical University 2-7 Daigakumachi Takatsuki 569-8686 Osaka Japan
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3
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Murakawa T, Suzuki M, Arima T, Sugahara M, Tanaka T, Tanaka R, Iwata S, Nango E, Tono K, Hayashi H, Fukui K, Yano T, Tanizawa K, Okajima T. Microcrystal preparation for serial femtosecond X-ray crystallography of bacterial copper amine oxidase. Acta Crystallogr F Struct Biol Commun 2021; 77:356-363. [PMID: 34605440 PMCID: PMC8488853 DOI: 10.1107/s2053230x21008967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Accepted: 08/28/2021] [Indexed: 11/10/2022] Open
Abstract
Recent advances in serial femtosecond X-ray crystallography (SFX) using X-ray free-electron lasers have paved the way for determining radiation-damage-free protein structures under nonfreezing conditions. However, the large-scale preparation of high-quality microcrystals of uniform size is a prerequisite for SFX, and this has been a barrier to its widespread application. Here, a convenient method for preparing high-quality microcrystals of a bacterial quinoprotein enzyme, copper amine oxidase from Arthrobacter globiformis, is reported. The method consists of the mechanical crushing of large crystals (5-15 mm3), seeding the crushed crystals into the enzyme solution and standing for 1 h at an ambient temperature of ∼26°C, leading to the rapid formation of microcrystals with a uniform size of 3-5 µm. The microcrystals diffracted X-rays to a resolution beyond 2.0 Å in SFX measurements at the SPring-8 Angstrom Compact Free Electron Laser facility. The damage-free structure determined at 2.2 Å resolution was essentially identical to that determined previously by cryogenic crystallography using synchrotron X-ray radiation.
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Affiliation(s)
- Takeshi Murakawa
- Department of Biochemistry, Faculty of Medicine, Osaka Medical and Pharmaceutical University, 2-7 Daigakumachi, Takatsuki, Osaka 569-8686, Japan
| | - Mamoru Suzuki
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Toshi Arima
- SPring-8 Center, RIKEN, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
- Department of Cell Biology, Graduate School of Medicine, Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Michihiro Sugahara
- SPring-8 Center, RIKEN, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
| | - Tomoyuki Tanaka
- SPring-8 Center, RIKEN, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
- Department of Cell Biology, Graduate School of Medicine, Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Rie Tanaka
- SPring-8 Center, RIKEN, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
- Department of Cell Biology, Graduate School of Medicine, Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
| | - So Iwata
- SPring-8 Center, RIKEN, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
- Department of Cell Biology, Graduate School of Medicine, Kyoto University, Yoshidakonoe-cho, Sakyo-ku, Kyoto 606-8501, Japan
| | - Eriko Nango
- SPring-8 Center, RIKEN, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
| | - Kensuke Tono
- SPring-8 Center, RIKEN, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
- Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan
| | - Hideyuki Hayashi
- Department of Chemistry, Faculty of Medicine, Osaka Medical and Pharmaceutical University, 2-7 Daigakumachi, Takatsuki, Osaka 569-8686, Japan
| | - Kenji Fukui
- Department of Biochemistry, Faculty of Medicine, Osaka Medical and Pharmaceutical University, 2-7 Daigakumachi, Takatsuki, Osaka 569-8686, Japan
| | - Takato Yano
- Department of Biochemistry, Faculty of Medicine, Osaka Medical and Pharmaceutical University, 2-7 Daigakumachi, Takatsuki, Osaka 569-8686, Japan
| | - Katsuyuki Tanizawa
- Institute of Scientific and Industrial Research (SANKEN), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
| | - Toshihide Okajima
- Department of Chemistry, Faculty of Medicine, Osaka Medical and Pharmaceutical University, 2-7 Daigakumachi, Takatsuki, Osaka 569-8686, Japan
- Institute of Scientific and Industrial Research (SANKEN), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
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4
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Neutron crystallography of copper amine oxidase reveals keto/enolate interconversion of the quinone cofactor and unusual proton sharing. Proc Natl Acad Sci U S A 2020; 117:10818-10824. [PMID: 32371483 DOI: 10.1073/pnas.1922538117] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Recent advances in neutron crystallographic studies have provided structural bases for quantum behaviors of protons observed in enzymatic reactions. Thus, we resolved the neutron crystal structure of a bacterial copper (Cu) amine oxidase (CAO), which contains a prosthetic Cu ion and a protein-derived redox cofactor, topa quinone (TPQ). We solved hitherto unknown structures of the active site, including a keto/enolate equilibrium of the cofactor with a nonplanar quinone ring, unusual proton sharing between the cofactor and the catalytic base, and metal-induced deprotonation of a histidine residue that coordinates to the Cu. Our findings show a refined active-site structure that gives detailed information on the protonation state of dissociable groups, such as the quinone cofactor, which are critical for catalytic reactions.
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5
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In crystallo thermodynamic analysis of conformational change of the topaquinone cofactor in bacterial copper amine oxidase. Proc Natl Acad Sci U S A 2018; 116:135-140. [PMID: 30563857 DOI: 10.1073/pnas.1811837116] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
In the catalytic reaction of copper amine oxidase, the protein-derived redox cofactor topaquinone (TPQ) is reduced by an amine substrate to an aminoresorcinol form (TPQamr), which is in equilibrium with a semiquinone radical (TPQsq). The transition from TPQamr to TPQsq is an endothermic process, accompanied by a significant conformational change of the cofactor. We employed the humid air and glue-coating (HAG) method to capture the equilibrium mixture of TPQamr and TPQsq in noncryocooled crystals of the enzyme from Arthrobacter globiformis and found that the equilibrium shifts more toward TPQsq in crystals than in solution. Thermodynamic analyses of the temperature-dependent equilibrium also revealed that the transition to TPQsq is entropy-driven both in crystals and in solution, giving the thermodynamic parameters that led to experimental determination of the crystal packing effect. Furthermore, we demonstrate that the binding of product aldehyde to the hydrophobic pocket in the active site produces various equilibrium states among two forms of the product Schiff-base, TPQamr, and TPQsq, in a pH-dependent manner. The temperature-controlled HAG method provides a technique for thermodynamic analysis of conformational changes occurring in protein crystals that are hardly scrutinized by conventional cryogenic X-ray crystallography.
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Papanikolaou MG, Hadjithoma S, Chatzikypraiou DS, Papaioannou D, Drouza C, Tsipis AC, Miras HN, Keramidas AD, Kabanos TA. Investigation of dioxygen activation by copper(ii)–iminate/aminate complexes. Dalton Trans 2018; 47:16242-16254. [DOI: 10.1039/c8dt03137a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
CuII amidate/iminate complexes activate dioxygen by a ligated to CuII, –HCN– moiety.
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Affiliation(s)
- Michael G. Papanikolaou
- Section of Inorganic and Analytical Chemistry
- Department of Chemistry
- University of Ioannina
- Ioannina 45110
- Greece
| | | | - Dimitra S. Chatzikypraiou
- Section of Inorganic and Analytical Chemistry
- Department of Chemistry
- University of Ioannina
- Ioannina 45110
- Greece
| | - Dionysios Papaioannou
- Laboratory of Synthetic Organic Chemistry
- Department of Chemistry
- University of Patras
- GR-26504 Patras
- Greece
| | - Chryssoula Drouza
- Department of Agricultural Sciences
- Biotechnology and Food Science
- Cyprus University of Technology
- Limassol 3036
- Cyprus
| | - Athanassios C. Tsipis
- Section of Inorganic and Analytical Chemistry
- Department of Chemistry
- University of Ioannina
- Ioannina 45110
- Greece
| | | | | | - Themistoklis A. Kabanos
- Section of Inorganic and Analytical Chemistry
- Department of Chemistry
- University of Ioannina
- Ioannina 45110
- Greece
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8
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Rao G, Bansal S, Law WX, O’Dowd B, Dikanov SA, Oldfield E. Pulsed Electron Paramagnetic Resonance Insights into the Ligand Environment of Copper in Drosophila Lysyl Oxidase. Biochemistry 2017; 56:3770-3779. [DOI: 10.1021/acs.biochem.7b00308] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Guodong Rao
- Department of Chemistry and ‡Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois 61801, United States
| | - Sandhya Bansal
- Department of Chemistry and ‡Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois 61801, United States
| | - Wen Xuan Law
- Department of Chemistry and ‡Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois 61801, United States
| | - Bing O’Dowd
- Department of Chemistry and ‡Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois 61801, United States
| | - Sergei A. Dikanov
- Department of Chemistry and ‡Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois 61801, United States
| | - Eric Oldfield
- Department of Chemistry and ‡Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois 61801, United States
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9
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Hirano Y, Chonan K, Murayama K, Sakasegawa SI, Matsumoto H, Sugimori D. Syncephalastrum racemosum amine oxidase with high catalytic efficiency toward ethanolamine and its application in ethanolamine determination. Appl Microbiol Biotechnol 2015; 100:3999-4013. [PMID: 26691518 DOI: 10.1007/s00253-015-7198-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 11/17/2015] [Accepted: 11/24/2015] [Indexed: 10/22/2022]
Abstract
Our screening study yielded a copper amine oxidase (SrAOX) from Syncephalastrum racemosum, which showed much higher affinity and catalytic efficiency toward ethanolamine (EA) than any other amine oxidase (AOX). Following purification of the enzyme to electrophoretic homogeneity from a cell-free extract, the maximum activity toward EA was detected at pH 7.2-7.5 and 45 °C. The SrAOX complementary DNA (cDNA) was composed of a 2052-bp open reading frame encoding a 683-amino acid protein with a molecular mass of 77,162 Da. The enzyme functions as a homodimer. The deduced amino acid sequence of SrAOX showed 55.3 % identity to Rhizopus delemar AOX and contains two consensus sequences of Cu-AOX, NYDY, and HHQH, suggesting SrAOX is a type 1 Cu-AOX (i.e., a topaquinone enzyme). Structural homology modeling showed that residues (112)ML(113), (141)FADTWG(146) M158, and N318 are unique, and T144 possibly characterizes the substrate specificity of SrAOX. The recombinant enzyme (rSrAOX) was produced using Escherichia coli. Steady-state kinetic analysis of rSrAOX activity toward EA (pH 7.5 and 45 °C) gave K m and k cat values of 0.848 ± 0.009 mM and 9.11 ± 0.13 s(-1), respectively. The standard curves were linear between 0.1 and 2 mM EA, and 10 μg mL(-1)-2.5 mg mL(-1) (15 μM-3.6 mM) phosphatidylethanolamine using Streptomyces chromofuscus phospholipase D, respectively, was sufficiently sensitive for clinical use.
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Affiliation(s)
- Yoshitaka Hirano
- Department of Symbiotic Systems Science and Technology, Graduate School of Symbiotic Systems Science and Technology, Fukushima University, 1 Kanayagawa, Fukushima, 960-1296, Japan
| | - Keisuke Chonan
- Department of Symbiotic Systems Science and Technology, Graduate School of Symbiotic Systems Science and Technology, Fukushima University, 1 Kanayagawa, Fukushima, 960-1296, Japan
| | - Kazutaka Murayama
- Division of Biomedical Measurements and Diagnostics, Graduate School of Biomedical Engineering, Tohoku University, 2-1 Seiryo, Aoba, Sendai, 980-8575, Japan
| | | | - Hideyuki Matsumoto
- Asahi Kasei Pharma Corp, 632-1 Mifuku, Izunokuni, Shizuoka, 410-2321, Japan
| | - Daisuke Sugimori
- Department of Symbiotic Systems Science and Technology, Graduate School of Symbiotic Systems Science and Technology, Fukushima University, 1 Kanayagawa, Fukushima, 960-1296, Japan.
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10
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Murakawa T, Hamaguchi A, Nakanishi S, Kataoka M, Nakai T, Kawano Y, Yamaguchi H, Hayashi H, Tanizawa K, Okajima T. Probing the Catalytic Mechanism of Copper Amine Oxidase from Arthrobacter globiformis with Halide Ions. J Biol Chem 2015; 290:23094-109. [PMID: 26269595 DOI: 10.1074/jbc.m115.662726] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Indexed: 11/06/2022] Open
Abstract
The catalytic reaction of copper amine oxidase proceeds through a ping-pong mechanism comprising two half-reactions. In the initial half-reaction, the substrate amine reduces the Tyr-derived cofactor, topa quinone (TPQ), to an aminoresorcinol form (TPQamr) that is in equilibrium with a semiquinone radical (TPQsq) via an intramolecular electron transfer to the active-site copper. We have analyzed this reductive half-reaction in crystals of the copper amine oxidase from Arthrobacter globiformis. Anerobic soaking of the crystals with an amine substrate shifted the equilibrium toward TPQsq in an "on-copper" conformation, in which the 4-OH group ligated axially to the copper center, which was probably reduced to Cu(I). When the crystals were soaked with substrate in the presence of halide ions, which act as uncompetitive and noncompetitive inhibitors with respect to the amine substrate and dioxygen, respectively, the equilibrium in the crystals shifted toward the "off-copper" conformation of TPQamr. The halide ion was bound to the axial position of the copper center, thereby preventing TPQamr from adopting the on-copper conformation. Furthermore, transient kinetic analyses in the presence of viscogen (glycerol) revealed that only the rate constant in the step of TPQamr/TPQsq interconversion is markedly affected by the viscogen, which probably perturbs the conformational change. These findings unequivocally demonstrate that TPQ undergoes large conformational changes during the reductive half-reaction.
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Affiliation(s)
- Takeshi Murakawa
- From the Department of Biochemistry, Osaka Medical College, Takatsuki, Osaka 569-8686, Japan
| | - Akio Hamaguchi
- the Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan
| | - Shota Nakanishi
- the Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan
| | - Misumi Kataoka
- the School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan, the Advanced Photon Technology Division, RIKEN SPring-8 Center, Sayo-gun, Hyogo 679-5148, Japan
| | - Tadashi Nakai
- the Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan
| | - Yoshiaki Kawano
- the Advanced Photon Technology Division, RIKEN SPring-8 Center, Sayo-gun, Hyogo 679-5148, Japan
| | - Hiroshi Yamaguchi
- the School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan, the Advanced Photon Technology Division, RIKEN SPring-8 Center, Sayo-gun, Hyogo 679-5148, Japan
| | - Hideyuki Hayashi
- the Department of Chemistry, Osaka Medical College, Takatsuki, Osaka 569-8686, Japan, and
| | - Katsuyuki Tanizawa
- the Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan, the Center of the Region Haná for Biotechnological and Agricultural Research, Faculty of Science, Palacký University, 783 71 Olomouc, Czech Republic
| | - Toshihide Okajima
- the Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan, the Department of Chemistry, Osaka Medical College, Takatsuki, Osaka 569-8686, Japan, and
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11
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Stylianou M, Drouza C, Giapintzakis J, Athanasopoulos GI, Keramidas AD. Aerial Oxidation of a V(IV)-Iminopyridine Hydroquinonate Complex: A Trap for the V(IV)-Semiquinonate Radical Intermediate. Inorg Chem 2015. [PMID: 26200893 DOI: 10.1021/acs.inorgchem.5b00571] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The reaction of 2,5-bis[N,N'-bis(2-pyridyl-aminomethyl)aminomethyl]-p-hydroquinone (H2bpymah) with VO(2+) salts in acetonitrile or water at a low pH (2.2-3.5) results in the isolation of [{V(IV)(O)(Cl)}2(μ-bpymah)], the p-semiquinonate complex [{V(IV)(O)(Cl)}2(μ-bpymas)](OH), the cyclic mixed-valent hexanuclear compound [{V(V)(O)(μ-O)V(IV)(O)}(μ-bpymah)]3, and [(V(V)O2)2(μ-bpymah)]. [{V(IV)(O)(Cl)}2(μ-bpymas)](OH) is an intermediate of the radical-mediated oxidation of [{V(IV)(O)(Cl)}2(μ-bpymah)] from O2. At lower pH values (2.2), a reversible intramolecular electron transfer from the metal to the ligand of [{V(IV)(O)(Cl)}2(μ-bpymas)](OH) is induced with the concurrent substitution of chlorine atoms by the oxygen-bridging atoms, resulting in the formation of [{V(V)(O)(μ-O)V(IV)(O)}(μ-bpymah)]3. The metal complexes were fully characterized by X-ray crystallography, infrared (IR) spectroscopy, and magnetic measurements in the solid state, as well as by conductivity measurements, UV-vis spectroscopy, and electrochemical measurements in solution. The oxidation states of the metal ions and ligands were determined by the crystallographic data. The [{V(IV)(O)(Cl)}2(μ-bpymah)]-[{V(IV)(O)(Cl)}2(μ-bpymas)](OH) redox process is electrochemically reversible. The V(IV) ion in the semiquinonate compound exhibits a surprisingly low oxophilicity, resulting in the stabilization of OH(-) counterions at acidic pH values. An investigation of the mechanism of this reaction reveals that these complexes induce the reduction of O2 to H2O2, mimicking the activity of enzymes incorporating two redox-active centers (metal-organic) in the active site.
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Affiliation(s)
- Marios Stylianou
- †Department of Chemistry, University of Cyprus, 1678 Nicosia, Cyprus
| | - Chryssoula Drouza
- ‡ Department of Agriculture Production, Biotechnology and Food Science, Cyprus University of Technology, 3036 Limasol, Cyprus
| | - John Giapintzakis
- §Department of Mechanical and Manufacturing Engineering, University of Cyprus, 1678 Nicosia, Cyprus
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12
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Shepard EM, Dooley DM. Inhibition and oxygen activation in copper amine oxidases. Acc Chem Res 2015; 48:1218-26. [PMID: 25897668 DOI: 10.1021/ar500460z] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Copper-containing amine oxidases (CuAOs) use both copper and 2,4,5-trihydroxyphenylalanine quinone (TPQ) to catalyze the oxidative deamination of primary amines. The CuAO active site is highly conserved and comprised of TPQ and a mononuclear type II copper center that exhibits five-coordinate, distorted square pyramidal coordination geometry with histidine ligands and equatorially and axially bound water in the oxidized, resting state. The active site is buried within the protein, and CuAOs from various sources display remarkable diversity with respect to the composition of the active site channel and cofactor accessibility. Structural and mechanistic factors that influence substrate preference and inhibitor sensitivity and selectivity have been defined. This Account summarizes the strategies used to design selective CuAO inhibitors based on active site channel characteristics, leading to either enhanced steric fits or the trapping of reactive electrophilic products. These findings provide a framework to support the future development of candidate molecules aimed at minimizing the negative side effects associated with drugs containing amine functionalities. This is vital given the existence of human diamine oxidase and vascular adhesion protein-1, which have distinct amine substrate preferences and are associated with different metabolic processes. Inhibition of these enzymes by antifungal or antiprotozoal agents, as well as classic monoamine oxidase (MAO) inhibitors, may contribute to the adverse side effects associated with drug treatment. These observations provide a rationale for the limited clinical value associated with certain amine-containing pharmaceuticals and emphasize the need for more selective AO inhibitors. This Account also discusses the novel roles of copper and TPQ in the chemistry of O2 activation and substrate oxidation. Reduced CuAOs exist in a redox equilibrium between the Cu(II)-TPQAMQ (aminoquinol) and Cu(I)-TPQSQ (semiquinone). Elucidating the roles of Cu(I), TPQSQ, and TPQAMQ in O2 activation, for example, distinguishing inner-sphere versus outer-sphere electron transfer mechanisms, has been actively investigated since the discovery of TPQSQ in 1991 and has only recently been clarified. Kinetics and spectroscopic studies encompassing metal substitution, stopped-flow and temperature-jump relaxation methods, and oxygen kinetic isotope experiments have provided strong support for an inner-sphere electron transfer step from Cu(I) to O2. Data for two enzymes support a mechanism wherein O2 prebinds to a three-coordinate Cu(I) site, yielding a [Cu(II)(η(1)-O2(-1))](+) intermediate, with H2O2 generated from ensuing rate-determining proton coupled electron transfer from TPQSQ. While kinetics data from the cobalt-substituted yeast enzyme indicated that O2 is reduced through an outer-sphere process involving TPQAMQ, new findings with a bacterial CuAO demonstrate that both the Cu(II) and Co(II) forms of the enzyme operate via parallel mechanisms involving metal-superoxide intermediates. Structural observations of a coordinated TPQSQ-Cu(I) complex in two CuAOs supports previous indications that Cu(II)/(I) ligand substitution chemistry may be mechanistically relevant. Substantial evidence indicates that rapid and reversible inner-sphere reduction of O2 at a three-coordinate Cu(I) site occurs, but the existence of a coordinated semiquinone in some AOs suggests that, in these enzymes, an outer-sphere reaction between O2 and TPQSQ may also be possible, since this is expected to be energetically favorable compared with outer-sphere electron transfer from TPQAMQ to O2.
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Affiliation(s)
- Eric M. Shepard
- Department
of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - David M. Dooley
- Office
of the President, University of Rhode Island, Kingston, Rhode Island 02881, United States
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