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Zaborowska-Mazurkiewicz M, Bizoń T, Matyszewska D, Fontaine P, Bilewicz R. Oxidation of lipid membrane cholesterol by cholesterol oxidase and its effects on raft model membrane structure. Colloids Surf B Biointerfaces 2024; 245:114191. [PMID: 39232481 DOI: 10.1016/j.colsurfb.2024.114191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2024] [Revised: 06/22/2024] [Accepted: 08/29/2024] [Indexed: 09/06/2024]
Abstract
The effects of a peripheral protein - cholesterol oxidase (3β-hydroxysteroid oxidase, ChOx) on the characteristics of model lipid membranes composed of cholesterol, cholesterol:sphingomyelin (1:1), and the raft model composed of DOPC:Chol:SM (1:1:1) were investigated using two membrane model systems: the flat monolayer prepared by the Langmuir technique and the curved model consisting of liposome of the same lipids. The planar monolayers and liposomes were employed to follow membrane cholesterol oxidation to cholestenone catalyzed by ChOx and changes in the lipid membrane structure accompanying this reaction. Changes in the structure of liposomes in the presence of the enzyme were reflected in the changes of hydrodynamic diameter and fluorescence microscopy images, while changes of surface properties of planar membranes were evaluated by grazing incidence X-ray diffraction (GIXD) and Brewster angle microscopy. UV-Vis absorbance measurements confirmed the activity of the enzyme in the tested systems. A better understanding of the interactions between the enzyme and the cell membrane may help in finding alternative ways to decrease excessive cholesterol levels than the common approach of treating hypercholesterolemia with statins, which are not free from undesirable side effects, repeatedly reported in the literature and observed by the patients.
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Affiliation(s)
| | - Teresa Bizoń
- Faculty of Physics, University of Warsaw, Pasteura 5, Warsaw 02093, Poland
| | - Dorota Matyszewska
- Faculty of Chemistry, Biological and Chemical Research Centre, University of Warsaw, Żwirki i Wigury 101, Warsaw 02089, Poland
| | - Philippe Fontaine
- Synchrotron Soleil, L'Orme des Merisiers, Départementale 128, Saint-Aubin 91190, France
| | - Renata Bilewicz
- Faculty of Chemistry, University of Warsaw, Pasteura 1, Warsaw 02093, Poland.
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2
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Oh C, Park B, Sundaresan V, Schaefer JL, Bohn PW. Closed Bipolar Electrode-Enabled Electrochromic Sensing of Multiple Metabolites in Whole Blood. ACS Sens 2023; 8:270-279. [PMID: 36547518 DOI: 10.1021/acssensors.2c02140] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
We report a closed bipolar electrode (CBE)-based sensing platform for the detection of diagnostic metabolites in undiluted whole human blood. The sensor is enabled by electrode chemistry based on: (1) a mixed layer of blood-compatible adsorption-resistant phosphorylcholine (PPC) and phenylbutyric acid (PBA), (2) ferrocene (Fc) redox mediators, and (3) immobilized redox-active enzymes. This scheme is designed to overcome nonspecific protein adsorption and amplify sensing currents in whole human fluids. The scheme also incorporates a diffusing mediator to increase electronic communication between the immobilized redox enzyme and the working electrode. The use of both bound and freely diffusing mediators is synergistic in producing the electrochemical response. The sensor is realized by linking the analyte cell, containing the specific electrode surface architecture, through a CBE to a reporter cell containing the electrochromic reporter, methyl viologen (MV). The colorless-to-purple color change accompanying the 1e- reduction of MV2+ is captured using a smartphone camera. Subsequent red-green-blue analysis is performed on the acquired images to determine cholesterol, glucose, and lactate concentrations in whole blood. The CBE blood metabolite sensor produces a linear color change at clinically relevant concentration ranges for all metabolites with good reproducibility (∼5% or better) and with limits of detection of 79 μM for cholesterol, 59 μM for glucose, and 86 μM for lactate. Finally, metabolite concentration measurements from the CBE blood metabolite sensor are compared with results from commercially available FDA-approved blood cholesterol, glucose, and lactate meters, with an average difference of ∼3.5% across all three metabolites in the ranges studied.
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Affiliation(s)
- Christiana Oh
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana46556, United States
| | - Bumjun Park
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana46556, United States
| | - Vignesh Sundaresan
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana46556, United States
| | - Jennifer L Schaefer
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana46556, United States
| | - Paul W Bohn
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana46556, United States.,Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana46556, United States
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3
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Mahmoud HE, El-Far SW, Embaby AM. Cloning, expression, and in silico structural modeling of cholesterol oxidase of Acinetobacter sp. strain RAMD in E. coli. FEBS Open Bio 2021; 11:2560-2575. [PMID: 34272838 PMCID: PMC8409315 DOI: 10.1002/2211-5463.13254] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 06/25/2021] [Accepted: 07/16/2021] [Indexed: 11/16/2022] Open
Abstract
Cholesterol oxidases (CHOXs) are flavin‐adenine dinucleotide‐dependent oxidoreductases with a range of biotechnological applications. There remains an urgent need to identify novel CHOX family members to meet the demands of enzyme markets worldwide. Here, we report the cloning, heterologous expression, and structural modeling of the cholesterol oxidase of Acinetobacter sp. strain RAMD. The cholesterol oxidase gene was cloned and expressed in pGEM®‐T and pET‐28a(+) vectors, respectively, using a gene‐specific primer based on the putative cholesterol oxidase ORF of Acinetobacter baumannii strain AB030 (GenBank [gb] locus tag: IX87_05230). The obtained nucleotide sequence (1671 bp, gb: MK575469.2), translated to a protein designated choxAB (556 amino acids), was overexpressed as inclusion bodies (IBs) (MW ˜ 62 kDa) in 1 mm IPTG‐induced Escherichia coli BL21 (DE3) Rosetta cells. The optimized expression conditions (1 mm IPTG with 2% [v/v] glycerol and at room temperature) yielded soluble active choxAB of 0.45 U·mL−1, with 56.25‐fold enhancement. The recombinant choxAB was purified to homogeneity using Ni2+‐affinity agarose column with specific activity (0.054 U·mg−1), yield (8.1%), and fold purification (11.69). Capillary isoelectric‐focusing indicated pI of 8.77 for choxAB. LC‐MS/MS confirmed the IBs (62 kDa), with 82.6% of the covered sequence being exclusive to A. baumannii cholesterol oxidase (UniProtKB: A0A0E1FG24). The 3D structure of choxAB was predicted using the LOMETS webtool with the cholesterol oxidase template of Streptomyces sp. SA‐COO (PDB: 2GEW). The predicted secondary structure included 18 α‐helices and 12 β‐strands, a predicted catalytic triad (E220, H380, and N514), and a conserved FAD‐binding sequence (GSGFGGSVSACRLTEKG). Future studies should consider fusion to solubilization tags and switching to the expression host Pichia pastoris to reduce IB formation.
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Affiliation(s)
- Hoda E Mahmoud
- Department of Biotechnology, Institute of Graduate Studies and Research, Alexandria University, Egypt
| | - Shaymaa W El-Far
- Division of Pharmaceutical Microbiology, Department of Pharmaceutics and Industrial Pharmacy, College of Pharmacy, Taif University, Saudi Arabia
| | - Amira M Embaby
- Department of Biotechnology, Institute of Graduate Studies and Research, Alexandria University, Egypt
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4
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Characterization and overproduction of cell-associated cholesterol oxidase ChoD from Streptomyces lavendulae YAKB-15. Sci Rep 2019; 9:11850. [PMID: 31413341 PMCID: PMC6694107 DOI: 10.1038/s41598-019-48132-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 07/25/2019] [Indexed: 11/30/2022] Open
Abstract
Cholesterol oxidases are important enzymes with a wide range of applications from basic research to industry. In this study, we have discovered and described the first cell-associated cholesterol oxidase, ChoD, from Streptomyces lavendulae YAKB-15. This strain is a naturally high producer of ChoD, but only produces ChoD in a complex medium containing whole yeast cells. For characterization of ChoD, we acquired a draft genome sequence of S. lavendulae YAKB-15 and identified a gene product containing a flavin adenine dinucleotide binding motif, which could be responsible for the ChoD activity. The enzymatic activity was confirmed in vitro with histidine tagged ChoD produced in Escherichia coli TOP10, which lead to the determination of basic kinetic parameters with Km 15.9 µM and kcat 10.4/s. The optimum temperature and pH was 65 °C and 5, respectively. In order to increase the efficiency of production, we then expressed the cholesterol oxidase, choD, gene heterologously in Streptomyces lividans TK24 and Streptomyces albus J1074 using two different expression systems. In S. albus J1074, the ChoD activity was comparable to the wild type S. lavendulae YAKB-15, but importantly allowed production of ChoD without the presence of yeast cells.
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5
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Erban T, Sopko B, Talacko P, Harant K, Kadlikova K, Halesova T, Riddellova K, Pekas A. Chronic exposure of bumblebees to neonicotinoid imidacloprid suppresses the entire mevalonate pathway and fatty acid synthesis. J Proteomics 2019; 196:69-80. [DOI: 10.1016/j.jprot.2018.12.022] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 12/07/2018] [Accepted: 12/20/2018] [Indexed: 11/16/2022]
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6
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Abstract
The gut microbiota plays a key role in cholesterol metabolism, mainly through the reduction of cholesterol to coprostanol. The latter sterol exhibits distinct physicochemical properties linked to its limited absorption in the gut. Few bacteria were reported to reduce cholesterol into coprostanol. Three microbial pathways of coprostanol production were described based on the analysis of reaction intermediates. However, these metabolic pathways and their associated genes remain poorly studied. In this review, we shed light on the microbial metabolic pathways related to coprostanol synthesis. Moreover, we highlight current strategies and future directions to better characterize these microbial enzymes and pathways.
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Zhang K, Huang M, Ma J, Liu Z, Zeng J, Liu X, Xu T, Wang X, Liu Y, Bu Z, Zhu Y. Identification and characterization of a novel bacterial pyranose 2-oxidase from the lignocellulolytic bacterium Pantoea ananatis Sd-1. Biotechnol Lett 2018; 40:871-880. [PMID: 29605940 DOI: 10.1007/s10529-018-2538-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Accepted: 03/06/2018] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To identify and characterize a novel bacterial pyranose 2-oxidase (P2Ox) and investigate its potential use in lignin degradation applications. RESULTS A new bacterial P2Ox (PaP2Ox) enzyme was identified in the lignocellulolytic bacterium Pantoea ananatis Sd-1. The PaP2Ox open reading frame was cloned, and the encoded protein was heterologously expressed in an Escherichia coli expression system. Unlike another reported bacterial P2Ox enzyme, the purified PaP2Ox exhibits a homotetrameric spatial conformation that is similar to fungal P2Oxs, with each subunit having a molecular mass of 65 kDa. The recombinant PaP2Ox exhibits maximum activity at 50 °C and pH 6.5 with D-glucose as its preferred substrate. In addition, this enzyme was shown to work in combination with bacterial laccase in lignin degradation. CONCLUSIONS The bacterial enzyme PaP2Ox has potential use in ligninolytic systems and shows promising value in industrial biotechnological applications.
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Affiliation(s)
- Keke Zhang
- Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha, 410008, Hunan, People's Republic of China
| | - Mei Huang
- Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha, 410008, Hunan, People's Republic of China
| | - Jiangshan Ma
- Hunan Academy of Forestry, Changsha, 410004, Hunan, People's Republic of China
| | - Zeyi Liu
- Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha, 410008, Hunan, People's Republic of China
| | - Jiarui Zeng
- Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha, 410008, Hunan, People's Republic of China
| | - Xuanming Liu
- Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha, 410008, Hunan, People's Republic of China
| | - Ting Xu
- Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha, 410008, Hunan, People's Republic of China
| | - Xiang Wang
- Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha, 410008, Hunan, People's Republic of China
| | - Ying Liu
- Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha, 410008, Hunan, People's Republic of China
| | - Zhigang Bu
- Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha, 410008, Hunan, People's Republic of China
| | - Yonghua Zhu
- Hunan Province Key Laboratory of Plant Functional Genomics and Developmental Regulation, College of Biology, Hunan University, Changsha, 410008, Hunan, People's Republic of China.
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8
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Fahrenbach VS, Bertaccini EJ. Insights Into Receptor-Based Anesthetic Pharmacophores and Anesthetic-Protein Interactions. Methods Enzymol 2018; 602:77-95. [PMID: 29588042 DOI: 10.1016/bs.mie.2018.01.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
General anesthetics are thought to allosterically bind and potentiate the inhibitory currents of the GABAA receptor through drug-specific binding sites. The physiologically relevant isoform of the GABAA receptor is a transmembrane ligand-gated ion channel consisting of five subunits (γ-α-β-α-β linkage) symmetrically arranged around a central chloride-conducting pore. Although the exact molecular structure of this heteropentameric GABAA receptor remains unknown, molecular modeling has allowed significant advancements in understanding anesthetic binding and action. Using the open-channel conformations of the homologous glycine and glutamate-gated chloride receptors as templates, a homology model of the GABAA receptor was constructed using the Discovery Studio computational chemistry software suite. Consensus structural alignment of the homology templates allowed for the construction of a three-dimensional heteropentameric GABAA receptor model with (γ2-β3-α1-β3-α1) subunit linkage. An anesthetic binding site was identified within the transmembrane α/β intersubunit space by the convergence of three residues shown to be essential for anesthetic activity in previous studies with mutant mice (β3-N265, β3-M286, α1-L232). Propofol derivatives docked into this binding site showed log-linear correlation with experimentally derived GABAA receptor potentiation (EC50) values, suggesting this binding site may be important for receptor activation. The receptor-based pharmacophore was analyzed with surface maps displaying the predominant anesthetic-protein interactions, revealing an amphiphilic binding cavity incorporating the three residues involved in anesthetic modulation. Quantum mechanics calculations of the bonding patterns found in complementary high-resolution receptor systems further elucidated the complex nature of anesthetic-protein interactions.
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Affiliation(s)
- Victoria S Fahrenbach
- Stanford University School of Medicine, Stanford, CA, United States; Palo Alto VA Health Care System, Palo Alto, CA, United States
| | - Edward J Bertaccini
- Stanford University School of Medicine, Stanford, CA, United States; Palo Alto VA Health Care System, Palo Alto, CA, United States.
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9
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Qin HM, Wang JW, Guo Q, Li S, Xu P, Zhu Z, Sun D, Lu F. Refolding of a novel cholesterol oxidase from Pimelobacter simplex reveals dehydrogenation activity. Protein Expr Purif 2017; 139:1-7. [DOI: 10.1016/j.pep.2017.07.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 07/11/2017] [Accepted: 07/12/2017] [Indexed: 11/26/2022]
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10
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Keirsse-Haquin J, Picaud T, Bordes L, de Gracia AG, Desbois A. Modulation of the flavin-protein interactions in NADH peroxidase and mercuric ion reductase: a resonance Raman study. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2017; 47:205-223. [PMID: 28889232 DOI: 10.1007/s00249-017-1245-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 07/12/2017] [Accepted: 07/26/2017] [Indexed: 10/18/2022]
Abstract
NADH peroxidase (Npx) and mercuric ion reductase (MerA) are flavoproteins belonging to the pyridine nucleotide:disulfide oxidoreductases (PNDO) and catalyzing the reduction of toxic substrates, i.e., hydrogen peroxide and mercuric ion, respectively. To determine the role of the flavin adenine dinucleotide (FAD) in the detoxification mechanism, the resonance Raman (RR) spectra of these enzymes under various redox and ligation states have been investigated using blue and/or near-UV excitation(s). These data were compared to those previously obtained for glutathione reductase (GR), another enzyme of the PNDO family, but catalyzing the reduction of oxidized glutathione. Spectral differences have been detected for the marker bands of the isoalloxazine ring of Npx, MerA, and GR. They provide evidence for different catalytic mechanisms in these flavoproteins. The RR modes of the oxidized and two-electron reduced (EH2) forms of Npx are related to very tight flavin-protein interactions maintaining a nearly planar conformation of the isoalloxazine tricycle, a low level of H-bonding at the N1/N5 and O2/O4 sites, and a strong H-bond at N3H. They also indicate minimal changes in FAD structure and environment upon either NAD(H) binding or reduction of the sulfinic redox center. All these spectroscopic data support an enzyme functioning centered on the Cys-SO-/Cys-S- redox moiety and a neighbouring His residue. On the contrary, the RR data on various functional forms of MerA are indicative of a modulation of both ring II distortion and H-bonding states of the N5 site and ring III. The Cd(II) binding to the EH2-NADP(H) complexes, biomimetic intermediates in the reaction of Hg(II) reduction, provokes important spectral changes. They are interpreted in terms of flattening of the isoalloxazine ring and large decreases in H-bonding at the N5 site and ring III. The large flexibility of the FAD structure and environment in MerA is in agreement with proposed mechanisms involving C4a(flavin) adducts.
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Affiliation(s)
- Julie Keirsse-Haquin
- Institut de Biologie Intégrative de la Cellule, UMR 9198 CNRS-CEA-Université Paris Sud, CEA Saclay, 91191, Gif-sur-Yvette Cedex, France.,Ecole Nationale Supérieure des Mines, 44300, Nantes, France
| | - Thierry Picaud
- Institut de Biologie Intégrative de la Cellule, UMR 9198 CNRS-CEA-Université Paris Sud, CEA Saclay, 91191, Gif-sur-Yvette Cedex, France.,Institut Supérieur des Biotechnologies de Paris (Sup'Biotech Paris), 94800, Villejuif, France
| | - Luc Bordes
- Institut de Biologie Intégrative de la Cellule, UMR 9198 CNRS-CEA-Université Paris Sud, CEA Saclay, 91191, Gif-sur-Yvette Cedex, France.,School of Earth and Environmental Sciences, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Adrienne Gomez de Gracia
- Institut de Biologie Intégrative de la Cellule, UMR 9198 CNRS-CEA-Université Paris Sud, CEA Saclay, 91191, Gif-sur-Yvette Cedex, France
| | - Alain Desbois
- Institut de Biologie Intégrative de la Cellule, UMR 9198 CNRS-CEA-Université Paris Sud, CEA Saclay, 91191, Gif-sur-Yvette Cedex, France.
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11
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Ozgur B, Ozdemir ES, Gursoy A, Keskin O. Relation between Protein Intrinsic Normal Mode Weights and Pre-Existing Conformer Populations. J Phys Chem B 2017; 121:3686-3700. [DOI: 10.1021/acs.jpcb.6b10401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Beytullah Ozgur
- Center for Computational Biology and Bioinformatics, ‡Chemical and Biological
Engineering, and §Computer Engineering,
College of Engineering, Koc University, 34450 Istanbul, Turkey
| | - E. Sila Ozdemir
- Center for Computational Biology and Bioinformatics, ‡Chemical and Biological
Engineering, and §Computer Engineering,
College of Engineering, Koc University, 34450 Istanbul, Turkey
| | - Attila Gursoy
- Center for Computational Biology and Bioinformatics, ‡Chemical and Biological
Engineering, and §Computer Engineering,
College of Engineering, Koc University, 34450 Istanbul, Turkey
| | - Ozlem Keskin
- Center for Computational Biology and Bioinformatics, ‡Chemical and Biological
Engineering, and §Computer Engineering,
College of Engineering, Koc University, 34450 Istanbul, Turkey
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12
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Vonck J, Parcej DN, Mills DJ. Structure of Alcohol Oxidase from Pichia pastoris by Cryo-Electron Microscopy. PLoS One 2016; 11:e0159476. [PMID: 27458710 PMCID: PMC4961394 DOI: 10.1371/journal.pone.0159476] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Accepted: 06/10/2016] [Indexed: 01/13/2023] Open
Abstract
The first step in methanol metabolism in methylotrophic yeasts, the oxidation of methanol and higher alcohols with molecular oxygen to formaldehyde and hydrogen peroxide, is catalysed by alcohol oxidase (AOX), a 600-kDa homo-octamer containing eight FAD cofactors. When these yeasts are grown with methanol as the carbon source, AOX forms large crystalline arrays in peroxisomes. We determined the structure of AOX by cryo-electron microscopy at a resolution of 3.4 Å. All residues of the 662-amino acid polypeptide as well as the FAD are well resolved. AOX shows high structural homology to other members of the GMC family of oxidoreductases, which share a conserved FAD binding domain, but have different substrate specificities. The preference of AOX for small alcohols is explained by the presence of conserved bulky aromatic residues near the active site. Compared to the other GMC enzymes, AOX contains a large number of amino acid inserts, the longest being 75 residues. These segments are found at the periphery of the monomer and make extensive inter-subunit contacts which are responsible for the very stable octamer. A short surface helix forms contacts between two octamers, explaining the tendency of AOX to form crystals in the peroxisomes.
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Affiliation(s)
- Janet Vonck
- Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
- * E-mail:
| | - David N. Parcej
- Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Deryck J. Mills
- Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
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13
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Membrane-associated glucose-methanol-choline oxidoreductase family enzymes PhcC and PhcD are essential for enantioselective catabolism of dehydrodiconiferyl alcohol. Appl Environ Microbiol 2015; 81:8022-36. [PMID: 26362985 DOI: 10.1128/aem.02391-15] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Accepted: 09/09/2015] [Indexed: 01/06/2023] Open
Abstract
Sphingobium sp. strain SYK-6 is able to degrade various lignin-derived biaryls, including a phenylcoumaran-type compound, dehydrodiconiferyl alcohol (DCA). In SYK-6 cells, the alcohol group of the B-ring side chain of DCA is initially oxidized to the carboxyl group to generate 3-(2-(4-hydroxy-3-methoxyphenyl)-3-(hydroxymethyl)-7-methoxy-2,3-dihydrobenzofuran-5-yl) acrylic acid (DCA-C). Next, the alcohol group of the A-ring side chain of DCA-C is oxidized to the carboxyl group, and then the resulting metabolite is catabolized through vanillin and 5-formylferulate. In this study, the genes involved in the conversion of DCA-C were identified and characterized. The DCA-C oxidation activities in SYK-6 were enhanced in the presence of flavin adenine dinucleotide and an artificial electron acceptor and were induced ca. 1.6-fold when the cells were grown with DCA. Based on these observations, SLG_09480 (phcC) and SLG_09500 (phcD), encoding glucose-methanol-choline oxidoreductase family proteins, were presumed to encode DCA-C oxidases. Analyses of phcC and phcD mutants indicated that PhcC and PhcD are essential for the conversion of (+)-DCA-C and (-)-DCA-C, respectively. When phcC and phcD were expressed in SYK-6 and Escherichia coli, the gene products were mainly observed in their membrane fractions. The membrane fractions of E. coli that expressed phcC and phcD catalyzed the specific conversion of DCA-C into the corresponding carboxyl derivatives. In the oxidation of DCA-C, PhcC and PhcD effectively utilized ubiquinone derivatives as electron acceptors. Furthermore, the transcription of a putative cytochrome c gene was significantly induced in SYK-6 grown with DCA. The DCA-C oxidation catalyzed by membrane-associated PhcC and PhcD appears to be coupled to the respiratory chain.
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14
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Statistical survey of the buried waters in the Protein Data Bank. Amino Acids 2015; 48:193-202. [PMID: 26315961 DOI: 10.1007/s00726-015-2064-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 07/29/2015] [Indexed: 12/18/2022]
Abstract
The structures of buried water molecules were studied in an ensemble of high-quality and non-redundant protein crystal structures. Buried water molecules were clustered and classified in lake-like clusters, which are completely isolated from the bulk solvent, and bay-like clusters, which are in contact with the bulk solvent through a surface water molecule. Buried water molecules are extremely common: lake-like clusters are found in 89 % of the protein crystal structures and bay-like clusters in 93 %. Clusters with only one water molecule are much more common than larger clusters. Both cluster types incline to be surrounded by loop residues, and to a minor extent by residues in extended secondary structure. Helical residues on the contrary do not tend to surround clusters of buried water molecules. One buried water molecule is found every 30-50 amino acid residues, depending on the secondary structures that are more abundant in the protein. Both main- and side-chain atoms are in contact with buried waters; they form four hydrogen bonds with the first water and 1-1.5 additional hydrogen bond for each additional water in the cluster. Consequently, buried water molecules appear to be firmly packed and rigid like the protein atoms. In this regard, it is remarkable to observe that prolines often surround water molecules buried in the protein interior. Interestingly, clusters of buried water molecules tend to be just beneath the protein surface. Moreover, water molecules tend to form a one-dimensional wire rather than more compact arrangements. This agrees with recent evidence of the mechanisms of solvent exchange between internal cavities and bulk solvent.
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15
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Golden E, Attwood PV, Duff AP, Meilleur F, Vrielink A. Production and characterization of recombinant perdeuterated cholesterol oxidase. Anal Biochem 2015; 485:102-8. [PMID: 26073659 DOI: 10.1016/j.ab.2015.06.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2015] [Revised: 06/04/2015] [Accepted: 06/05/2015] [Indexed: 10/23/2022]
Abstract
Cholesterol oxidase (CO) is a FAD (flavin adenine dinucleotide) containing enzyme that catalyzes the oxidization and isomerization of cholesterol. Studies directed toward elucidating the catalytic mechanism of CO will provide an important general understanding of Flavin-assisted redox catalysis. Hydrogen atoms play an important role in enzyme catalysis; however, they are not readily visualized in protein X-ray diffraction structures. Neutron crystallography is an ideal method for directly visualizing hydrogen positions at moderate resolutions because hydrogen and deuterium have comparable neutron scattering lengths to other heavy atoms present in proteins. The negative coherent and large incoherent scattering lengths of hydrogen atoms in neutron diffraction experiments can be circumvented by replacing hydrogen atoms with its isotope, deuterium. The perdeuterated form of CO was successfully expressed from minimal medium, purified, and crystallized. X-ray crystallographic structures of the enzyme in the perdeuterated and hydrogenated states confirm that there are no apparent structural differences between the two enzyme forms. Kinetic assays demonstrate that perdeuterated and hydrogenated enzymes are functionally identical. Together, structural and functional studies indicate that the perdeuterated protein is suitable for structural studies by neutron crystallography directed at understanding the role of hydrogen atoms in enzyme catalysis.
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Affiliation(s)
- Emily Golden
- School of Chemistry and Biochemistry, University of Western Australia, Crawley, WA 6009, Australia
| | - Paul V Attwood
- School of Chemistry and Biochemistry, University of Western Australia, Crawley, WA 6009, Australia
| | - Anthony P Duff
- Bragg Institute, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia
| | - Flora Meilleur
- Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA; Structural and Molecular Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
| | - Alice Vrielink
- School of Chemistry and Biochemistry, University of Western Australia, Crawley, WA 6009, Australia.
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16
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Faletrov YV, Frolova NS, Hlushko HV, Rudaya EV, Edimecheva IP, Mauersberger S, Shkumatov VM. Evaluation of the fluorescent probes Nile Red and 25-NBD-cholesterol as substrates for steroid-converting oxidoreductases using pure enzymes and microorganisms. FEBS J 2013; 280:3109-19. [DOI: 10.1111/febs.12265] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Revised: 03/21/2013] [Accepted: 03/21/2013] [Indexed: 11/30/2022]
Affiliation(s)
- Yaroslav V. Faletrov
- Research Institute for Physical Chemical Problems; Belarusian State University; Minsk; Belarus
| | - Nina S. Frolova
- Research Institute for Physical Chemical Problems; Belarusian State University; Minsk; Belarus
| | - Hanna V. Hlushko
- Research Institute for Physical Chemical Problems; Belarusian State University; Minsk; Belarus
| | - Elena V. Rudaya
- Research Institute for Physical Chemical Problems; Belarusian State University; Minsk; Belarus
| | - Irina P. Edimecheva
- Research Institute for Physical Chemical Problems; Belarusian State University; Minsk; Belarus
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17
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Hernández-Ortega A, Lucas F, Ferreira P, Medina M, Guallar V, Martínez AT. Role of Active Site Histidines in the Two Half-Reactions of the Aryl-Alcohol Oxidase Catalytic Cycle. Biochemistry 2012; 51:6595-608. [DOI: 10.1021/bi300505z] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Fátima Lucas
- Joint BSC-IRB
Research Program
in Computational Biology, Barcelona Supercomputing Center, Jordi Girona 29, E-08034 Barcelona, Spain
| | - Patricia Ferreira
- Department of Biochemistry and
Molecular and Cellular Biology and Institute of Biocomputation and
Physics of Complex Systems, University of Zaragoza, E-50009 Zaragoza, Spain
| | - Milagros Medina
- Department of Biochemistry and
Molecular and Cellular Biology and Institute of Biocomputation and
Physics of Complex Systems, University of Zaragoza, E-50009 Zaragoza, Spain
| | - Victor Guallar
- Joint BSC-IRB
Research Program
in Computational Biology, Barcelona Supercomputing Center, Jordi Girona 29, E-08034 Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys 23, E-08010 Barcelona, Spain
| | - Angel T. Martínez
- Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040
Madrid, Spain
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18
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Wallner S, Winkler A, Riedl S, Dully C, Horvath S, Gruber K, Macheroux P. Catalytic and structural role of a conserved active site histidine in berberine bridge enzyme. Biochemistry 2012; 51:6139-47. [PMID: 22757961 PMCID: PMC3413249 DOI: 10.1021/bi300411n] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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Berberine bridge enzyme (BBE) is a paradigm for the class
of bicovalently
flavinylated oxidases, which catalyzes the oxidative cyclization of
(S)-reticuline to (S)-scoulerine.
His174 was identified as an important active site residue because
of its role in the stabilization of the reduced state of the flavin
cofactor. It is also strictly conserved in the family of BBE-like
oxidases. Here, we present a detailed biochemical and structural characterization
of a His174Ala variant supporting its importance during catalysis
and for the structural organization of the active site. Substantial
changes in all kinetic parameters and a decrease in midpoint potential
were observed for the BBE His174Ala variant protein. Moreover, the
crystal structure of the BBE His174Ala variant showed significant
structural rearrangements compared to wild-type enzyme. On the basis
of our findings, we propose that His174 is part of a hydrogen bonding
network that stabilizes the negative charge at the N1–C2=O
locus via interaction with the hydroxyl group at C2′ of the
ribityl side chain of the flavin cofactor. Hence, replacement of this
residue with alanine reduces the stabilizing effect for the transiently
formed negative charge and results in drastically decreased kinetic
parameters as well as a lower midpoint redox potential.
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Affiliation(s)
- Silvia Wallner
- Institute of Biochemistry, Graz University of Technology, Petersgasse 12/2, A-8010 Graz, Austria
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19
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García JL, Uhía I, Galán B. Catabolism and biotechnological applications of cholesterol degrading bacteria. Microb Biotechnol 2012; 5:679-99. [PMID: 22309478 PMCID: PMC3815891 DOI: 10.1111/j.1751-7915.2012.00331.x] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Cholesterol is a steroid commonly found in nature with a great relevance in biology, medicine and chemistry, playing an essential role as a structural component of animal cell membranes. The ubiquity of cholesterol in the environment has made it a reference biomarker for environmental pollution analysis and a common carbon source for different microorganisms, some of them being important pathogens such as Mycobacterium tuberculosis. This work revises the accumulated biochemical and genetic knowledge on the bacterial pathways that degrade or transform this molecule, given that the characterization of cholesterol metabolism would contribute not only to understand its role in tuberculosis but also to develop new biotechnological processes that use this and other related molecules as starting or target materials.
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Affiliation(s)
- J L García
- Environmental Biology Department, Centro de Investigaciones Biológicas, CSIC, C/ Ramiro de Maeztu, 9, 28040 Madrid, Spain.
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20
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Viswanathan S, Li P, Choi W, Filipek S, Balasubramaniam TA, Renugopalakrishnan V. Protein-carbon nanotube sensors: single platform integrated micro clinical lab for monitoring blood analytes. Methods Enzymol 2012; 509:165-94. [PMID: 22568906 DOI: 10.1016/b978-0-12-391858-1.00010-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Design of a unique, single-platform, integrated, multichannel sensor based on carbon nanotube (CNT)-protein adducts specific to each one of the major analytes of blood, glucose, cholesterol, triglyceride, and Hb1AC is presented. The concept underlying the sensor, amperometric detection, is applicable to various disease-monitoring strategies. There is an urgent need to enhance the sensitivity of glucometers to <5% level instead of greater than the present 15% standard in these detectors. CNTs enhance the signals derived from the interaction of the enzymes with the different analytes in blood. Fabricated sensors using the new methodology is a point-of-care device that is targeted for home, clinical, and emergency use and can be redesigned for continuous monitoring for critical care patients.
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Affiliation(s)
- Sowmya Viswanathan
- Newton-Wellesley Hospital/Partners Healthcare System, Newton, Massachusetts, USA
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21
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22
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Wongnate T, Sucharitakul J, Chaiyen P. Identification of a Catalytic Base for Sugar Oxidation in the Pyranose 2-Oxidase Reaction. Chembiochem 2011; 12:2577-86. [DOI: 10.1002/cbic.201100564] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2011] [Indexed: 11/10/2022]
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23
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Improvement of the thermostability and enzymatic activity of cholesterol oxidase by site-directed mutagenesis. Biotechnol Lett 2011; 33:2049-55. [PMID: 21701916 DOI: 10.1007/s10529-011-0669-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Accepted: 06/01/2011] [Indexed: 10/18/2022]
Abstract
Site-directed mutagenesis was applied to enhance the thermostability and enzymatic activity of cholesterol oxidase (ChOx) isolated from Brevibacterium sp. Three amino acid residues (Q153E, F128L, and S143H) located near the FAD-binding site of the enzyme were substituted based on structural analysis. The specific activity of the two-sites mutant Q153E/F128L increased by 11.6% and the relative activity increased by 47% when grown for 2 h at 50 °C. This mutant is a potential industrial strain for producing ChOx.
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24
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Uhía I, Galán B, Morales V, García JL. Initial step in the catabolism of cholesterol by Mycobacterium smegmatis mc2155. Environ Microbiol 2011; 13:943-59. [DOI: 10.1111/j.1462-2920.2010.02398.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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25
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Tan YW, Yang H. Seeing the forest for the trees: fluorescence studies of single enzymes in the context of ensemble experiments. Phys Chem Chem Phys 2010; 13:1709-21. [PMID: 21183988 DOI: 10.1039/c0cp02412k] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Enzymes are remarkable molecular machines that make many difficult biochemical reactions possible under mild biological conditions with incredible precision and efficiency. Our understanding of the working principles of enzymes, however, has not reached the level where one can readily deduce the mechanism and the catalytic rates from an enzyme's structure. Resolving the dynamics that relate the three-dimensional structure of an enzyme to its function has been identified as a key issue. While still challenging to implement, single-molecule techniques have emerged as one of the most useful methods for studying enzymes. We review enzymes studied using single-molecule fluorescent methods but placing them in the context of results from other complementary experimental work done on bulk samples. This review primarily covers three enzyme systems--flavoenzymes, dehydrofolate reductase, and adenylate kinase--with additional enzymes mentioned where appropriate. When the single-molecule experiments are discussed together with other methods aiming at the same scientific question, the weakness, strength, and unique contributions become clear.
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Affiliation(s)
- Yan-Wen Tan
- Department of Physics, Fudan University, No. 220, Handan Rd., Shanghai 200433, China.
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26
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Maeda Y, Doubayashi D, Ootake T, Oki M, Mikami B, Uchida H. Crystallization and preliminary X-ray analysis of formate oxidase, an enzyme of the glucose-methanol-choline oxidoreductase family. Acta Crystallogr Sect F Struct Biol Cryst Commun 2010; 66:1064-6. [PMID: 20823527 DOI: 10.1107/s1744309110028605] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 07/17/2010] [Indexed: 05/26/2023]
Abstract
Formate oxidase (FOD), which catalyzes the oxidation of formate to yield carbon dioxide and hydrogen peroxide, belongs to the glucose-methanol-choline oxidoreductase (GMCO) family. FOD from Aspergillus oryzae RIB40, which has a modified FAD as a cofactor, was crystallized at 293 K by the hanging-drop vapour-diffusion method. The crystal was orthorhombic and belonged to space group C222(1). Diffraction data were collected from a single crystal to 2.4 A resolution.
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Affiliation(s)
- Yoshifumi Maeda
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, 9-1 Bunkyo 3-chome, Fukui-shi 910-8507, Japan
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27
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Leopoldini M, Russo N, Toscano M. Favored Reaction Mechanism of Calcium-Dependent Phospholipase A2. Insights from Density Functional Exploration. J Phys Chem B 2010; 114:11584-93. [DOI: 10.1021/jp1003819] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Monica Leopoldini
- Dipartimento di Chimica and Centro di Calcolo ad Alte Prestazioni per Elaborazioni Parallele e Distribuite-Centro d’Eccellenza MIUR, Università della Calabria, I-87030 Arcavacata di Rende (CS), Italy
| | - Nino Russo
- Dipartimento di Chimica and Centro di Calcolo ad Alte Prestazioni per Elaborazioni Parallele e Distribuite-Centro d’Eccellenza MIUR, Università della Calabria, I-87030 Arcavacata di Rende (CS), Italy
| | - Marirosa Toscano
- Dipartimento di Chimica and Centro di Calcolo ad Alte Prestazioni per Elaborazioni Parallele e Distribuite-Centro d’Eccellenza MIUR, Università della Calabria, I-87030 Arcavacata di Rende (CS), Italy
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28
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Abstract
Cholesterol oxidase is a bacterial-specific flavoenzyme that catalyzes the oxidation and isomerisation of steroids containing a 3beta hydroxyl group and a double bond at the Delta5-6 of the steroid ring system. The enzyme is a member of a large family of flavin-specific oxidoreductases and is found in two different forms: one where the flavin adenine dinucleotide (FAD) cofactor is covalently linked to the protein and one where the cofactor is non-covalently bound to the protein. These two enzyme forms have been extensively studied in order to gain insight into the mechanism of flavin-mediated oxidation and the relationship between protein structure and enzyme redox potential. More recently the enzyme has been found to play an important role in bacterial pathogenesis and hence further studies are focused on its potential use for future development of novel antibacterial therapeutic agents. In this review the biochemical, structural, kinetic and mechanistic features of the enzyme are discussed.
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29
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Mowat CG, Gazur B, Campbell LP, Chapman SK. Flavin-containing heme enzymes. Arch Biochem Biophys 2010; 493:37-52. [DOI: 10.1016/j.abb.2009.10.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2009] [Revised: 10/13/2009] [Accepted: 10/13/2009] [Indexed: 11/25/2022]
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30
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Abstract
Cholesterol is a major constituent of the plasma membrane in eukaryotic cells. It regulates the physical state of the phospholipid bilayer and is crucially involved in the formation of membrane microdomains. Cholesterol also affects the activity of several membrane proteins, and is the precursor for steroid hormones and bile acids. Here, methods are described that are used to explore the binding and/or interaction of proteins to cholesterol. For this purpose, a variety of cholesterol probes bearing radio-, spin-, photoaffinity- or fluorescent labels are currently available. Examples of proven cholesterol binding molecules are polyene compounds, cholesterol-dependent cytolysins, enzymes accepting cholesterol as substrate, and proteins with cholesterol binding motifs. Main topics of this report are the localization of candidate membrane proteins in cholesterol-rich microdomains, the issue of specificity of cholesterol- protein interactions, and applications of the various cholesterol probes for these studies.
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Affiliation(s)
- Gerald Gimpl
- Institut für Biochemie, Johannes Gutenberg-Universität, Johann-Joachim-Becherweg 30, Mainz, Germany.
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31
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Lyubimov AY, Chen L, Sampson NS, Vrielink A. A hydrogen-bonding network is important for oxidation and isomerization in the reaction catalyzed by cholesterol oxidase. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2009; 65:1222-31. [PMID: 19923719 PMCID: PMC3089011 DOI: 10.1107/s0907444909037421] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Accepted: 09/16/2009] [Indexed: 11/10/2022]
Abstract
Cholesterol oxidase is a flavoenzyme that catalyzes the oxidation and isomerization of 3beta-hydroxysteroids. Structural and mutagenesis studies have shown that Asn485 plays a key role in substrate oxidation. The side chain makes an NH...pi interaction with the reduced form of the flavin cofactor. A N485D mutant was constructed to further test the role of the amide group in catalysis. The mutation resulted in a 1800-fold drop in the overall k(cat). Atomic resolution structures were determined for both the N485L and N485D mutants. The structure of the N485D mutant enzyme (at 1.0 A resolution) reveals significant perturbations in the active site. As predicted, Asp485 is oriented away from the flavin moiety, such that any stabilizing interaction with the reduced flavin is abolished. Met122 and Glu361 form unusual hydrogen bonds to the functional group of Asp485 and are displaced from the positions they occupy in the wild-type active site. The overall effect is to disrupt the stabilization of the reduced FAD cofactor during catalysis. Furthermore, a narrow transient channel that is shown to form when the wild-type Asn485 forms the NH...pi interaction with FAD and that has been proposed to function as an access route of molecular oxygen, is not observed in either of the mutant structures, suggesting that the dynamics of the active site are altered.
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Affiliation(s)
- Artem Y Lyubimov
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, Sinsheimer Laboratories, Santa Cruz, CA 95064, USA
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32
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Abstract
An important aspect of catalysis performed by cholesterol oxidase (3beta-hydroxysteroid oxidase) concerns the nature of its association with the lipid bilayer that contains the sterol substrate. Efficient catalytic turnover is affected by the association of the protein with the membrane as well as the solubility of the substrate in the lipid bilayer. In this review, the binding of cholesterol oxidase to the lipid bilayer, its turnover of substrates presented in different physical environments, and how these conditions affect substrate specificity, are discussed. The physiological functions of the enzyme in bacterial metabolism, pathogenesis and macrolide biosynthesis are reviewed in this context.
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Affiliation(s)
- Joseph Kreit
- Laboratory of Biochemistry and Immunology, Department of Biology, Faculty of Sciences, Mohammed V University, Rabat, Morocco
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33
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Abstract
Cholesterol oxidases are bifunctional flavoenzymes that catalyze the oxidation of steroid substrates which have a hydroxyl group at the 3beta position of the steroid ring system. The enzyme is found, in a wide range of bacterial species, in two forms: one with the FAD cofactor bound noncovalently to the enzyme; and one with the cofactor linked covalently to the protein. Here we discuss, compare and contrast the salient biochemical properties of the two forms of the enzyme. Specifically, the structural features are discussed that affect the redox potentials of the flavin cofactor, the chemical mechanism of substrate dehydrogenation by active-center amino acid residues, the kinetic parameters of both types of enzymes and the reactivity of reduced enzymes with molecular dioxygen. The presence of a molecular tunnel that is proposed to serve in the access of dioxygen to the active site and mechanisms of its control by a 'gate' formed by amino acid residues are highlighted.
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Affiliation(s)
- Alice Vrielink
- School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, Crawley, Australia.
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34
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Oxidation of amines by flavoproteins. Arch Biochem Biophys 2009; 493:13-25. [PMID: 19651103 DOI: 10.1016/j.abb.2009.07.019] [Citation(s) in RCA: 166] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2009] [Revised: 07/27/2009] [Accepted: 07/29/2009] [Indexed: 11/21/2022]
Abstract
Many flavoproteins catalyze the oxidation of primary and secondary amines, with the transfer of a hydride equivalent from a carbon-nitrogen bond to the flavin cofactor. Most of these amine oxidases can be classified into two structural families, the D-amino acid oxidase/sarcosine oxidase family and the monoamine oxidase family. This review discusses the present understanding of the mechanisms of amine and amino acid oxidation by flavoproteins, focusing on these two structural families.
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35
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Doukyu N. Characteristics and biotechnological applications of microbial cholesterol oxidases. Appl Microbiol Biotechnol 2009; 83:825-37. [PMID: 19495743 DOI: 10.1007/s00253-009-2059-8] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2009] [Revised: 05/22/2009] [Accepted: 05/23/2009] [Indexed: 11/27/2022]
Abstract
Microbial cholesterol oxidase is an enzyme of great commercial value, widely employed by laboratories routinely devoted to the determination of cholesterol concentrations in serum, other clinical samples, and food. In addition, the enzyme has potential applications as a biocatalyst which can be used as an insecticide and for the bioconversion of a number of sterols and non-steroidal alcohols. The enzyme has several biological roles, which are implicated in the cholesterol metabolism, the bacterial pathogenesis, and the biosynthesis of macrolide antifungal antibiotics. Cholesterol oxidase has been reported from a variety of microorganisms, mostly from actinomycetes. We recently reported cholesterol oxidases from gram-negative bacteria such as Burkholderia and Chromobacterium. These enzymes possess thermal, detergent, and organic solvent tolerance. There are two forms of cholesterol oxidase, one containing a flavin adenine dinucleotide cofactor non-covalently bound to the enzyme (class I) and the other containing the cofactor covalently linked to the enzyme (class II). These two enzymes have no significant sequence homology. The phylogenetic tree analyses show that both class I and class II enzymes can be further divided into at least two groups.
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Affiliation(s)
- Noriyuki Doukyu
- Bio-Nano Electronic Research Center, Toyo University, Kujirai, Kawagoe, Saitama, Japan.
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36
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Overexpression, one-step purification, and characterization of a type II cholesterol oxidase from a local isolate Rhodococcus sp. PTCC 1633. World J Microbiol Biotechnol 2009. [DOI: 10.1007/s11274-008-9948-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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37
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Ghasemian A, T. Yazdi M, Sepehrizad Z. Construction of a Thermally Stable Cholesterol Oxidase Mutant by Site-Directed Mutagenesis. ACTA ACUST UNITED AC 2008. [DOI: 10.3923/biotech.2008.826.829] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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38
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Piubelli L, Pedotti M, Molla G, Feindler-Boeckh S, Ghisla S, Pilone MS, Pollegioni L. On the oxygen reactivity of flavoprotein oxidases: an oxygen access tunnel and gate in brevibacterium sterolicum cholesterol oxidase. J Biol Chem 2008; 283:24738-47. [PMID: 18614534 DOI: 10.1074/jbc.m802321200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The flavoprotein cholesterol oxidase from Brevibacterium sterolicum (BCO) possesses a narrow channel that links the active center containing the flavin to the outside solvent. This channel has been proposed to serve for the access of dioxygen; it contains at its "bottom" a Glu-Arg pair (Glu-475-Arg-477) that was found by crystallographic studies to exist in two forms named "open" and "closed," which in turn was suggested to constitute a gate functioning in the control of oxygen access. Most mutations of residues that flank the channel have minor effects on the oxygen reactivity. Mutations of Glu-311, however, cause a switch in the basic kinetic mechanism of the reaction of reduced BCO with dioxygen; wild-type BCO and most mutants show a saturation behavior with increasing oxygen concentration, whereas for Glu-311 mutants a linear dependence is found that is assumed to reflect a "simple" second order process. This is taken as support for the assumption that residue Glu-311 finely tunes the Glu-475-Arg-477 pair, forming a gate that functions in modulating the access/reactivity of dioxygen.
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Affiliation(s)
- Luciano Piubelli
- Department of Biotechnology and Molecular Sciences, University of Insubria, 21100 Varese, Italy
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39
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Michalski C, Mohagheghi H, Nimtz M, Pasteels J, Ober D. Salicyl alcohol oxidase of the chemical defense secretion of two chrysomelid leaf beetles. Molecular and functional characterization of two new members of the glucose-methanol-choline oxidoreductase gene family. J Biol Chem 2008; 283:19219-28. [PMID: 18482980 DOI: 10.1074/jbc.m802236200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Salicyl alcohol oxidase is an extracellular enzyme that occurs in glandular reservoirs of chrysomelid leaf beetle larvae and catalyzes the formation of salicylaldehyde, a volatile deterrent used by the larvae against predators. Salicyl alcohol is the hydrolysis product of salicin, a plant-derived precursor taken up by the beetle larvae from the leaves of willow and poplar trees. The cDNA encoding salicyl alcohol oxidase from two related species Chrysomela tremulae and Chrysomela populi has been identified, cloned, and expressed in an active form in Escherichia coli. The open reading frame of 623 amino acids begins in both enzymes with an N-terminal signal peptide of 21 amino acids. Sequence comparison has revealed that salicyl alcohol oxidase belongs to the family of glucose-methanol-choline oxidoreductase-like sequences with mostly unknown function. Enzymes of this family share similar overall structure with an essentially identical FAD-binding site but possess different catalytic activities. The data suggest that salicyl alcohol oxidase, essential for the activation of the plant-derived precursor salicin, was originally recruited from an oxidase involved in the autogenous biosynthesis of iridoid monoterpenes and found in related chrysomelid leaf beetle species.
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Affiliation(s)
- Carmen Michalski
- Botanisches Institut und Botanischer Garten, Universität Kiel, Olshausenstrasse 40, 24098 Kiel, Germany
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40
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Abstract
Cholesterol is a major constituent of the membranes in most eukaryotic cells where it fulfills multiple functions. Cholesterol regulates the physical state of the phospholipid bilayer, affects the activity of several membrane proteins, and is the precursor for steroid hormones and bile acids. Cholesterol plays a crucial role in the formation of membrane microdomains such as "lipid rafts" and caveolae. However, our current understanding on the membrane organization, intracellular distribution and trafficking of cholesterol is rather poor. This is mainly due to inherent difficulties to label and track this small lipid. In this review, we describe different approaches to detect cholesterol in vitro and in vivo. Cholesterol reporter molecules can be classified in two groups: cholesterol binding molecules and cholesterol analogues. The enzyme cholesterol oxidase is used for the determination of cholesterol in serum and food. Susceptibility to cholesterol oxidase can provide information about localization, transfer kinetics, or transbilayer distribution of cholesterol in membranes and cells. The polyene filipin forms a fluorescent complex with cholesterol and is commonly used to visualize the cellular distribution of free cholesterol. Perfringolysin O, a cholesterol binding cytolysin, selectively recognizes cholesterol-rich structures. Photoreactive cholesterol probes are appropriate tools to analyze or to identify cholesterol binding proteins. Among the fluorescent cholesterol analogues one can distinguish probes with intrinsic fluorescence (e.g., dehydroergosterol) from those possessing an attached fluorophore group. We summarize and critically discuss the features of the different cholesterol reporter molecules with a special focus on recent imaging approaches.
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Affiliation(s)
- Gerald Gimpl
- Institut für Biochemie, Johannes Gutenberg-University of Mainz, Becherweg 30, 55099, Mainz, Germany.
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41
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Lyubimov AY, Heard K, Tang H, Sampson NS, Vrielink A. Distortion of flavin geometry is linked to ligand binding in cholesterol oxidase. Protein Sci 2008; 16:2647-56. [PMID: 18029419 DOI: 10.1110/ps.073168207] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Two high-resolution structures of a double mutant of bacterial cholesterol oxidase in the presence or absence of a ligand, glycerol, are presented, showing the trajectory of glycerol as it binds in a Michaelis complex-like position in the active site. A group of three aromatic residues forces the oxidized isoalloxazine moiety to bend along the N5-N10 axis as a response to the binding of glycerol in the active site. Movement of these aromatic residues is only observed in the glycerol-bound structure, indicating that some tuning of the FAD redox potential is caused by the formation of the Michaelis complex during regular catalysis. This structural study suggests a possible mechanism of substrate-assisted flavin activation, improves our understanding of the interplay between the enzyme, its flavin cofactor and its substrate, and is of use to the future design of effective cholesterol oxidase inhibitors.
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Affiliation(s)
- Artem Y Lyubimov
- Department of Molecular Cell and Developmental Biology, University of California, Santa Cruz, California 95064, USA
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42
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Aparicio JF, Martín JF. Microbial cholesterol oxidases: bioconversion enzymes or signal proteins? MOLECULAR BIOSYSTEMS 2008; 4:804-9. [DOI: 10.1039/b717500k] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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43
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Mendes MV, Recio E, Antón N, Guerra SM, Santos-Aberturas J, Martín JF, Aparicio JF. Cholesterol Oxidases Act as Signaling Proteins for the Biosynthesis of the Polyene Macrolide Pimaricin. ACTA ACUST UNITED AC 2007; 14:279-90. [PMID: 17379143 DOI: 10.1016/j.chembiol.2007.01.010] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Revised: 01/11/2007] [Accepted: 01/17/2007] [Indexed: 11/27/2022]
Abstract
The gene cluster responsible for pimaricin biosynthesis in Streptomyces natalensis contains a cholesterol oxidase-encoding gene (pimE) surrounded by genes involved in pimaricin production. Gene-inactivation and -complementation experiments revealed that pimE encodes a functional cholesterol oxidase and, surprisingly, that it is also involved in pimaricin biosynthesis. This extracellular enzyme was purified from S. natalensis culture broths to homogeneity, and it was shown to restore pimaricin production when added to the mutant culture broths. Other cholesterol oxidases also triggered pimaricin production, suggesting that these enzymes could act as signaling proteins for polyene biosynthesis. This finding constitutes the description of a cholesterol oxidase gene with an involvement in antibiotic biosynthesis, and it broadens the scope of the biological functions for this type of oxidase.
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44
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Kujawa M, Volc J, Halada P, Sedmera P, Divne C, Sygmund C, Leitner C, Peterbauer C, Haltrich D. Properties of pyranose dehydrogenase purified from the litter-degrading fungus Agaricus xanthoderma. FEBS J 2007; 274:879-94. [PMID: 17227387 DOI: 10.1111/j.1742-4658.2007.05634.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We purified an extracellular pyranose dehydrogenase (PDH) from the basidiomycete fungus Agaricus xanthoderma using ammonium sulfate fractionation and ion-exchange and hydrophobic interaction chromatography. The native enzyme is a monomeric glycoprotein (5% carbohydrate) containing a covalently bound FAD as its prosthetic group. The PDH polypeptide consists of 575 amino acids and has a molecular mass of 65 400 Da as determined by MALDI MS. On the basis of the primary structure of the mature protein, PDH is a member of the glucose-methanol-choline oxidoreductase family. We constructed a homology model of PDH using the 3D structure of glucose oxidase from Aspergillus niger as a template. This model suggests a novel type of bi-covalent flavinylation in PDH, 9-S-cysteinyl, 8-alpha-N3-histidyl FAD. The enzyme exhibits a broad sugar substrate tolerance, oxidizing structurally different aldopyranoses including monosaccharides and oligosaccharides as well as glycosides. Its preferred electron donor substrates are D-glucose, D-galactose, L-arabinose, and D-xylose. As shown by in situ NMR analysis, D-glucose and D-galactose are both oxidized at positions C2 and C3, yielding the corresponding didehydroaldoses (diketoaldoses) as the final reaction products. PDH shows no detectable activity with oxygen, and its reactivity towards electron acceptors is rather limited, reducing various substituted benzoquinones and complexed metal ions. The azino-bis-(3-ethylbenzthiazolin-6-sulfonic acid) cation radical and the ferricenium ion are the best electron acceptors, as judged by the catalytic efficiencies (k(cat)/K(m)). The enzyme may play a role in lignocellulose degradation.
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Affiliation(s)
- Magdalena Kujawa
- Division of Food Biotechnology, Department of Food Sciences and Technology, BOKU - University of Natural Resources and Applied Life Sciences, Vienna, Austria
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45
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Alva S, Phadk RS, Govil G. Synthesis and LB Film Formation of Fatty Acid- Fad Complex. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/10587259308055186] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Shridhara Alva
- a Chemical Physics Group , Tata Institute of Fundamental Research , Bombay , 400 005 , India
| | - Ratna S. Phadk
- a Chemical Physics Group , Tata Institute of Fundamental Research , Bombay , 400 005 , India
| | - Girjesh Govil
- a Chemical Physics Group , Tata Institute of Fundamental Research , Bombay , 400 005 , India
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46
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Lim L, Molla G, Guinn N, Ghisla S, Pollegioni L, Vrielink A. Structural and kinetic analyses of the H121A mutant of cholesterol oxidase. Biochem J 2006; 400:13-22. [PMID: 16856877 PMCID: PMC1635447 DOI: 10.1042/bj20060664] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Cholesterol oxidase is a monomeric flavoenzyme that catalyses the oxidation of cholesterol to cholest-5-en-3-one followed by isomerization to cholest-4-en-3-one. The enzyme from Brevibacterium sterolicum contains the FAD cofactor covalently bound to His121. It was previously demonstrated that the H121A substitution results in a approximately 100 mV decrease in the midpoint redox potential and a approximately 40-fold decrease in turnover number compared to wild-type enzyme [Motteran, Pilone, Molla, Ghisla and Pollegioni (2001) Journal of Biological Chemistry 276, 18024-18030]. A detailed kinetic analysis of the H121A mutant enzyme shows that the decrease in turnover number is largely due to a corresponding decrease in the rate constant of flavin reduction, whilst the re-oxidation reaction is only marginally altered and the isomerization reaction is not affected by the substitution and precedes product dissociation. The X-ray structure of the mutant protein, determined to 1.7 A resolution (1 A identical with 0.1 nm), reveals only minor changes in the overall fold of the protein, namely: two loops have slight movements and a tryptophan residue changes conformation by a rotation of 180 degrees about chi1 compared to the native enzyme. Comparison of the isoalloxazine ring moiety of the FAD cofactor between the structures of the native and mutant proteins shows a change from a non-planar to a planar geometry (resulting in a more tetrahedral-like geometry for N5). This change is proposed to be a major factor contributing to the observed alteration in redox potential. Since a similar distortion of the flavin has not been observed in other covalent flavoproteins, it is proposed to represent a specific mode to facilitate flavin reduction in covalent cholesterol oxidase.
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Affiliation(s)
- Louis Lim
- *Department of Chemistry and Biochemistry, Sinsheimer Laboratory, University of California at Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064, U.S.A
| | - Gianluca Molla
- †Department of Biotechnology and Molecular Sciences, University of Insubria, via J.H. Dunant 3, 21100 Varese, Italy
| | - Nicole Guinn
- *Department of Chemistry and Biochemistry, Sinsheimer Laboratory, University of California at Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064, U.S.A
| | - Sandro Ghisla
- ‡Fachbereich Biologie, University of Konstanz, Konstanz, Germany
| | - Loredano Pollegioni
- †Department of Biotechnology and Molecular Sciences, University of Insubria, via J.H. Dunant 3, 21100 Varese, Italy
| | - Alice Vrielink
- *Department of Chemistry and Biochemistry, Sinsheimer Laboratory, University of California at Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064, U.S.A
- To whom correspondence should be addressed (email )
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Ferreira P, Ruiz-Dueñas FJ, Martínez MJ, van Berkel WJH, Martínez AT. Site-directed mutagenesis of selected residues at the active site of aryl-alcohol oxidase, an H2O2-producing ligninolytic enzyme. FEBS J 2006; 273:4878-88. [PMID: 16999821 DOI: 10.1111/j.1742-4658.2006.05488.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Aryl-alcohol oxidase provides H(2)O(2) for lignin biodegradation, a key process for carbon recycling in land ecosystems that is also of great biotechnological interest. However, little is known of the structural determinants of the catalytic activity of this fungal flavoenzyme, which oxidizes a variety of polyunsaturated alcohols. Different alcohol substrates were docked on the aryl-alcohol oxidase molecular structure, and six amino acid residues surrounding the putative substrate-binding site were chosen for site-directed mutagenesis modification. Several Pleurotus eryngii aryl-alcohol oxidase variants were purified to homogeneity after heterologous expression in Emericella nidulans, and characterized in terms of their steady-state kinetic properties. Two histidine residues (His502 and His546) are strictly required for aryl-alcohol oxidase catalysis, as shown by the lack of activity of different variants. This fact, together with their location near the isoalloxazine ring of FAD, suggested a contribution to catalysis by alcohol activation, enabling its oxidation by flavin-adenine dinucleotide (FAD). The presence of two aromatic residues (at positions 92 and 501) is also required, as shown by the conserved activity of the Y92F and F501Y enzyme variants and the strongly impaired activity of Y92A and F501A. By contrast, a third aromatic residue (Tyr78) does not seem to be involved in catalysis. The kinetic and spectral properties of the Phe501 variants suggested that this residue could affect the FAD environment, modulating the catalytic rate of the enzyme. Finally, L315 affects the enzyme k(cat), although it is not located in the near vicinity of the cofactor. The present study provides the first evidence for the role of aryl-alcohol oxidase active site residues.
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Affiliation(s)
- Patricia Ferreira
- Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040 Madrid, Spain
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48
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Kujawa M, Ebner H, Leitner C, Hallberg BM, Prongjit M, Sucharitakul J, Ludwig R, Rudsander U, Peterbauer C, Chaiyen P, Haltrich D, Divne C. Structural basis for substrate binding and regioselective oxidation of monosaccharides at C3 by pyranose 2-oxidase. J Biol Chem 2006; 281:35104-15. [PMID: 16984920 DOI: 10.1074/jbc.m604718200] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pyranose 2-oxidase (P2Ox) participates in fungal lignin degradation by producing the H2O2 needed for lignin-degrading peroxidases. The enzyme oxidizes cellulose- and hemicellulose-derived aldopyranoses at C2 preferentially, but also on C3, to the corresponding ketoaldoses. To investigate the structural determinants of catalysis, covalent flavinylation, substrate binding, and regioselectivity, wild-type and mutant P2Ox enzymes were produced and characterized biochemically and structurally. Removal of the histidyl-FAD linkage resulted in a catalytically competent enzyme containing tightly, but noncovalently bound FAD. This mutant (H167A) is characterized by a 5-fold lower kcat, and a 35-mV lower redox potential, although no significant structural changes were seen in its crystal structure. In previous structures of P2Ox, the substrate loop (residues 452-457) covering the active site has been either disordered or in a conformation incompatible with carbohydrate binding. We present here the crystal structure of H167A in complex with a slow substrate, 2-fluoro-2-deoxy-D-glucose. Based on the details of 2-fluoro-2-deoxy-D-glucose binding in position for oxidation at C3, we also outline a probable binding mode for D-glucose positioned for regioselective oxidation at C2. The tentative determinant for discriminating between the two binding modes is the position of the O6 hydroxyl group, which in the C2-oxidation mode can make favorable interactions with Asp452 in the substrate loop and, possibly, a nearby arginine residue (Arg472). We also substantiate our hypothesis with steady-state kinetics data for the alanine replacements of Asp452 and Arg472 as well as the double alanine 452/472 mutant.
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Affiliation(s)
- Magdalena Kujawa
- School of Biotechnology, Royal Institute of Technology, Albanova University Center, SE-106 91 Stockholm, Sweden
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49
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Bannwarth M, Heckmann-Pohl D, Bastian S, Giffhorn F, Schulz GE. Reaction Geometry and Thermostable Variant of Pyranose 2-Oxidase from the White-Rot Fungus Peniophora sp.,. Biochemistry 2006; 45:6587-95. [PMID: 16716069 DOI: 10.1021/bi052465d] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Pyranose 2-oxidase catalyzes the oxidation of a number of carbohydrates using dioxygen; glucose, for example, is oxidized at carbon 2. The structure of pyranose 2-oxidase with the reaction product 2-keto-beta-d-glucose bound in the active center is reported in a new crystal form at 1.41 A resolution. The binding structure suggests that the alpha-anomer cannot be processed. The binding mode of the oxidized product was used to model other sugars accepted by the enzyme and to explain its specificity and catalytic rates. The reported structure at pH 6.0 shows a drastic conformational change in the loop of residues 454-461 (loop 454-461) at the active center compared to that of a closely homologous enzyme analyzed at pH 4.5 with a bound acetate inhibitor. In our structures, the loop is highly mobile and shifts to make way for the sugar to pass into the active center. Presumably, loop 454-461 functions as a gatekeeper. Apart from the wild-type enzyme, a thermostable variant was analyzed at 1.84 A resolution. In this variant, Glu542 is exchanged for a lysine. The observed stabilization could be a result of the mutated residue changing an ionic contact at a comparatively weak interface of the tetramer.
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Affiliation(s)
- Michael Bannwarth
- Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität, Albertstrasse 21, 79104 Freiburg im Breisgau, Germany
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50
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Ghanem M, Gadda G. Effects of reversing the protein positive charge in the proximity of the flavin N(1) locus of choline oxidase. Biochemistry 2006; 45:3437-47. [PMID: 16519539 DOI: 10.1021/bi052514m] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A protein positive charge near the flavin N(1) locus is a distinguishing feature of most flavoprotein oxidases, with mechanistic implications for the modulation of flavin reactivity. A recent study showed that in the active site of choline oxidase the protein positive charge is provided by His(466). Here, we have reversed the charge by substitution with aspartate (CHO-H466D) and, for the first time, characterized a flavoprotein oxidase with a negative charge near the flavin N(1) locus. CHO-H466D formed a stable complex with choline but lost the ability to oxidize the substrate. In contrast to the wild-type enzyme, which binds FAD covalently in a 1:1 ratio, CHO-H466D contained approximately 0.3 FAD per protein, of which 75% was not covalently bound to the enzyme. Anaerobic reduction of CHO-H466D resulted in the formation of a neutral hydroquinone, with no stabilization of the flavin semiquinone; in contrast, the anionic semiquinone and hydroquinone species were observed with the wild type and a H466A variant of the enzyme. The midpoint reduction potential for the oxidized-reduced couple in CHO-H466D was approximately 160 mV lower than that of the wild-type enzyme. Finally, CHO-H466D lost the ability to form complexes with glycine betaine or sulfite. Thus, with a reversal of the protein charge near the FAD N(1) locus, choline oxidase lost the ability to stabilize negative charges in the active site, irrespective of whether they develop on the flavin or are borne on ligands, resulting in defective flavinylation of the protein, the decreased electrophilicity of the flavin, and the consequent loss of catalytic activity.
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Affiliation(s)
- Mahmoud Ghanem
- Department of Chemistry, Georgia State University, Atlanta, Georgia 30302-4098, USA
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