1
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Pierdominici‐Sottile G, Palma J, Ferrelli ML, Sobrado P. The dynamics of the flavin, NADPH, and active site loops determine the mechanism of activation of class B flavin-dependent monooxygenases. Protein Sci 2024; 33:e4935. [PMID: 38501462 PMCID: PMC10962481 DOI: 10.1002/pro.4935] [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: 10/11/2023] [Revised: 02/02/2024] [Accepted: 02/06/2024] [Indexed: 03/20/2024]
Abstract
Flavin-dependent monooxygenases (FMOs) constitute a diverse enzyme family that catalyzes crucial hydroxylation, epoxidation, and Baeyer-Villiger reactions across various metabolic pathways in all domains of life. Due to the intricate nature of this enzyme family's mechanisms, some aspects of their functioning remain unknown. Here, we present the results of molecular dynamics computations, supplemented by a bioinformatics analysis, that clarify the early stages of their catalytic cycle. We have elucidated the intricate binding mechanism of NADPH and L-Orn to a class B monooxygenase, the ornithine hydroxylase fromAspergillus $$ Aspergillus $$ fumigatus $$ fumigatus $$ known as SidA. Our investigation involved a comprehensive characterization of the conformational changes associated with the FAD (Flavin Adenine Dinucleotide) cofactor, transitioning from the out to the in position. Furthermore, we explored the rotational dynamics of the nicotinamide ring of NADPH, shedding light on its role in facilitating FAD reduction, supported by experimental evidence. Finally, we also analyzed the extent of conservation of two Tyr-loops that play critical roles in the process.
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Affiliation(s)
- Gustavo Pierdominici‐Sottile
- Departamento de Ciencia y TecnologíaUniversidad Nacional de QuilmesBernalArgentina
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)CABAArgentina
| | - Juliana Palma
- Departamento de Ciencia y TecnologíaUniversidad Nacional de QuilmesBernalArgentina
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)CABAArgentina
| | - María Leticia Ferrelli
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)CABAArgentina
- Instituto de Biotecnología y Biología Molecular (IBBM, UNLP‐CONICET), Facultad de Ciencias ExactasUniversidad Nacional de La PlataLa PlataBuenos AiresArgentina
| | - Pablo Sobrado
- Department of BiochemistryVirginia TechBlacksburgVirginiaUSA
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2
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Pereira MS, de Araújo SS, Nagem RAP, Richard JP, Brandão TAS. The role of remote flavin adenine dinucleotide pieces in the oxidative decarboxylation catalyzed by salicylate hydroxylase. Bioorg Chem 2022; 119:105561. [PMID: 34965488 PMCID: PMC8824312 DOI: 10.1016/j.bioorg.2021.105561] [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: 09/17/2021] [Revised: 11/19/2021] [Accepted: 12/11/2021] [Indexed: 02/03/2023]
Abstract
Salicylate hydroxylase (NahG) has a single redox site in which FAD is reduced by NADH, the O2 is activated by the reduced flavin, and salicylate undergoes an oxidative decarboxylation by a C(4a)-hydroperoxyflavin intermediate to give catechol. We report experimental results that show the contribution of individual pieces of the FAD cofactor to the observed enzymatic activity for turnover of the whole cofactor. A comparison of the kinetic parameters and products for the NahG-catalyzed reactions of FMN and riboflavin cofactor fragments reveal that the adenosine monophosphate (AMP) and ribitol phosphate pieces of FAD act to anchor the flavin to the enzyme and to direct the partitioning of the C(4a)-hydroperoxyflavin reaction intermediate towards hydroxylation of salicylate. The addition of AMP or ribitol phosphate pieces to solutions of the truncated flavins results in a partial restoration of the enzymatic activity lost upon truncation of FAD, and the pieces direct the reaction of the C(4a)-hydroperoxyflavin intermediate towards hydroxylation of salicylate.
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Affiliation(s)
- Mozart S. Pereira
- Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901, Brazil
| | - Simara S. de Araújo
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901, Brazil
| | - Ronaldo A. P. Nagem
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901, Brazil
| | - John P. Richard
- Department of Chemistry, University at Buffalo, SUNY, Buffalo, New York 14260-3000,CORRESPONDING AUTHOR: ;
| | - Tiago A. S. Brandão
- Departamento de Química, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Belo Horizonte, MG 31270-901, Brazil.,CORRESPONDING AUTHOR: ;
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3
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Meng L, Sun C, Gao L, Saleem M, Li B, Wang C. Hydroxybenzoate hydroxylase genes underlying protocatechuic acid production in Valsa mali are required for full pathogenicity in apple trees. MOLECULAR PLANT PATHOLOGY 2021; 22:1370-1382. [PMID: 34390112 PMCID: PMC8518569 DOI: 10.1111/mpp.13119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 07/01/2021] [Accepted: 07/20/2021] [Indexed: 06/13/2023]
Abstract
Valsa mali is the causative agent of apple tree valsa canker, which causes significant losses in apple production. It produces various toxic compounds that kill plant cells, facilitating infection. Among these, protocatechuic acid exhibits the highest phytotoxic activity. However, those genes involved in toxin production have not been studied. In this study we identified four hydroxybenzoate hydroxylase genes (VmHbh1, VmHbh2, VmHbh3, and VmHbh4) from the transcriptome of V. mali. The VmHbh protein had high enzymatic activities of hydroxybenzoate hydroxylase, which could convert 4-hydroxybenzoate to protocatechuic acid. These four VmHbh genes all had highly elevated transcript levels during the V. mali infection process, especially VmHbh1 and VmHbh4, with 26.0- and 53.4-fold increases, respectively. Mutants of the four genes were generated to study whether VmHbhs are required for V. mali pathogenicity. Of the four genes, the VmHbh1 and VmHbh4 deletion mutants considerably attenuated V. mali virulence in apple leaves and in twigs, coupled with much reduced toxin levels. The VmHbh2 and VmHbh3 deletion mutants promoted the transcript levels of the other VmHbhs, suggesting functional redundancies of VmHbhs in V. mali virulence. The results provide insights into the functions of VmHbhs in the production of protocatechuic acid by V. mali during its infection of apple trees.
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Affiliation(s)
- Lulu Meng
- College of Plant Health and MedicineKey Laboratory of Integrated Crop Pest Management of Shandong ProvinceShandong Province Key Laboratory of Applied MycologyQingdao Agricultural UniversityQingdaoChina
| | - Cuicui Sun
- College of Plant Health and MedicineKey Laboratory of Integrated Crop Pest Management of Shandong ProvinceShandong Province Key Laboratory of Applied MycologyQingdao Agricultural UniversityQingdaoChina
| | - Liyong Gao
- College of Plant Health and MedicineKey Laboratory of Integrated Crop Pest Management of Shandong ProvinceShandong Province Key Laboratory of Applied MycologyQingdao Agricultural UniversityQingdaoChina
| | - Muhammad Saleem
- Department of Biological SciencesAlabama State UniversityMontgomeryAlabamaUSA
| | - Baohua Li
- College of Plant Health and MedicineKey Laboratory of Integrated Crop Pest Management of Shandong ProvinceShandong Province Key Laboratory of Applied MycologyQingdao Agricultural UniversityQingdaoChina
| | - Caixia Wang
- College of Plant Health and MedicineKey Laboratory of Integrated Crop Pest Management of Shandong ProvinceShandong Province Key Laboratory of Applied MycologyQingdao Agricultural UniversityQingdaoChina
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4
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Reis RAG, Li H, Johnson M, Sobrado P. New frontiers in flavin-dependent monooxygenases. Arch Biochem Biophys 2021; 699:108765. [PMID: 33460580 DOI: 10.1016/j.abb.2021.108765] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 01/08/2021] [Accepted: 01/11/2021] [Indexed: 12/15/2022]
Abstract
Flavin-dependent monooxygenases catalyze a wide variety of redox reactions in important biological processes and are responsible for the synthesis of highly complex natural products. Although much has been learned about FMO chemistry in the last ~80 years of research, several aspects of the reactions catalyzed by these enzymes remain unknown. In this review, we summarize recent advancements in the flavin-dependent monooxygenase field including aspects of flavin dynamics, formation and stabilization of reactive species, and the hydroxylation mechanism. Novel catalysis of flavin-dependent N-oxidases involving consecutive oxidations of amines to generate oximes or nitrones is presented and the biological relevance of the products is discussed. In addition, the activity of some FMOs have been shown to be essential for the virulence of several human pathogens. We also discuss the biomedical relevance of FMOs in antibiotic resistance and the efforts to identify inhibitors against some members of this important and growing family enzymes.
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Affiliation(s)
| | - Hao Li
- Department of Biochemistry, Blacksburg, VA, 24061, USA
| | - Maxim Johnson
- Department of Biochemistry, Blacksburg, VA, 24061, USA
| | - Pablo Sobrado
- Department of Biochemistry, Blacksburg, VA, 24061, USA; Center for Drug Discovery, Virginia Tech, Blacksburg, VA, 24061, USA.
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5
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Toplak M, Matthews A, Teufel R. The devil is in the details: The chemical basis and mechanistic versatility of flavoprotein monooxygenases. Arch Biochem Biophys 2020; 698:108732. [PMID: 33358998 DOI: 10.1016/j.abb.2020.108732] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 12/15/2020] [Accepted: 12/19/2020] [Indexed: 02/07/2023]
Abstract
The ubiquitous flavoenzymes commonly catalyze redox chemistry such as the monooxygenation of organic substrates and are both widely utilized in nature (e.g., in primary and secondary metabolism) and of significant industrial interest. In this work, we highlight the structural and mechanistic characteristics of the distinct types of flavoprotein monooxygenases (FPMOs). We thereby illustrate the chemical basis of FPMO catalysis, which enables reactions such as (aromatic) hydroxylation, epoxidation, (de)halogenation, heteroatom oxygenation, Baeyer-Villiger oxidation, α-hydroxylation of ketones, or non-oxidative carbon-hetero bond cleavage. This seemingly unmatched versatility in oxygenation chemistry results from extensive fine-tuning and regiospecific functionalization of the flavin cofactor that is tightly controlled by the surrounding protein matrix. Accordingly, FPMOs steer the formation of covalent flavin-oxygen adducts for oxygen transfer in the form of the classical flavin-C4a-(hydro)peroxide or the recently discovered N5-functionalized flavins (i.e. the flavin-N5-oxide and the flavin-N5-peroxide), while in rare cases covalent oxygen adduct formation may be foregone entirely. Finally, we speculate about hitherto undiscovered flavin-mediated oxygenation reactions and compare FPMOs to cytochrome P450 monooxygenases, before addressing open questions and challenges for the future investigation of FPMOs.
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Affiliation(s)
- Marina Toplak
- Faculty of Biology, University of Freiburg, 79104, Freiburg, Germany
| | - Arne Matthews
- Faculty of Biology, University of Freiburg, 79104, Freiburg, Germany
| | - Robin Teufel
- Faculty of Biology, University of Freiburg, 79104, Freiburg, Germany.
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6
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In silico methods predict new blood-brain barrier permeable structure for the inhibition of kynurenine 3-monooxygenase. J Mol Graph Model 2020; 100:107701. [PMID: 32805560 DOI: 10.1016/j.jmgm.2020.107701] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Revised: 06/14/2020] [Accepted: 07/10/2020] [Indexed: 11/23/2022]
Abstract
Kynurenine 3-monooxygenase (KMO) regulates the levels of bioactive substances in the kynurenine pathway of tryptophan catabolism and its activity is tied to so many diseases that finding an appropriate inhibitor for KMO has become an urgent task. This especially proved to be difficult for the central nervous system related diseases due to the requirement that the supposed inhibitor should be both blood brain barrier permeable and should not cause hydrogen peroxide as a harmful side product. In this in silico study, we present our step-wise approach, whose starting point is based on the important experimental observations. To tackle the problem, a library of 7561938 structures was obtained from Zinc15 database utilizing the tranche browser. From this library, a subset of 501777 structures was determined with the considerations of their functional groups that constrain their applicability. Then, the binding affinity ranking of this set of structures was determined via virtual screening. Starting from the structures whose affinities are the highest among this subset, the ADMET properties were checked through in silico methods and the binding properties of the selected inhibitor candidates were further investigated via molecular dynamics simulations and MM/GBSA calculations. According to the computational results of this study, ZINC_71915355 has passed all the evaluations and is a potentially BBB permeable structure that can inhibit KMO. Additionally, ZINC_19827377 was identified as a new potential KMO inhibitor which may be more suitable for peripheral administration. From the in silico study presented herein, ZINC_71915355 and ZINC_19827377 structures, which showed high binding affinity without harmful H2O2 production, along with the tailored properties can now serve as powerful candidates for KMO inhibition and these hits are worth of further experimental validation.
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7
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Guarneri A, Westphal AH, Leertouwer J, Lunsonga J, Franssen MCR, Opperman DJ, Hollmann F, Berkel WJH, Paul CE. Flavoenzyme‐mediated Regioselective Aromatic Hydroxylation with Coenzyme Biomimetics. ChemCatChem 2020. [DOI: 10.1002/cctc.201902044] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Alice Guarneri
- Laboratory of Organic ChemistryWageningen University Stippeneng 4 Wageningen 6708 WE The Netherlands
| | - Adrie H. Westphal
- Laboratory of BiochemistryWageningen University Stippeneng 4 Wageningen 6708 WE The Netherlands
| | - Jos Leertouwer
- Department of BiotechnologyDelft University of Technology Van der Maasweg 9 Delft 2629 HZ The Netherlands
| | - Joy Lunsonga
- Laboratory of Organic ChemistryWageningen University Stippeneng 4 Wageningen 6708 WE The Netherlands
| | - Maurice C. R. Franssen
- Laboratory of Organic ChemistryWageningen University Stippeneng 4 Wageningen 6708 WE The Netherlands
| | - Diederik J. Opperman
- Department of BiotechnologyUniversity of the Free State 205 Nelson Mandela Drive Bloemfontein 9300 South Africa
| | - Frank Hollmann
- Department of BiotechnologyDelft University of Technology Van der Maasweg 9 Delft 2629 HZ The Netherlands
| | - Willem J. H. Berkel
- Laboratory of Food ChemistryWageningen University Bornse Weilanden 9 Wageningen 6708 WG The Netherlands
| | - Caroline E. Paul
- Department of BiotechnologyDelft University of Technology Van der Maasweg 9 Delft 2629 HZ The Netherlands
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8
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Doubayashi D, Oki M, Mikami B, Uchida H. The microenvironment surrounding FAD mediates its conversion to 8-formyl-FAD in Aspergillus oryzae RIB40 formate oxidase. J Biochem 2019; 166:67-75. [PMID: 30715389 DOI: 10.1093/jb/mvz009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 01/29/2019] [Indexed: 11/15/2022] Open
Abstract
Aspergillus oryzae RIB40 formate oxidase has Arg87 and Arg554 near the formyl group and O(4) atom of 8-formyl-flavin adenine dinucleotide (FAD), respectively, with Asp396 neighbouring Arg554. Herein, we probed the roles of these three residues in modification of FAD to 8-formyl-FAD. Replacement of Arg87 or Arg554 with Lys or Ala decreased and abolished the modification, respectively. Replacement of Asp396 with Ala or Asn lowered the modification rate. The observation of unusual effects of maintaining pH 7.0 on the modification in R87K, R554K and D396 variants indicates initial and subsequent processes with different pH dependencies. Comparison of the initial process at pH 4.5 and 7.0 suggests that the microenvironment around Arg87 and the protonation state of Asp396 affect the initial process in the native enzyme. Comparison of the crystal structures of native and R554 variants showed that the replacements had minimal effect on catalytic site structure. The positively charged Arg87 might contribute to the formation of an anionic quinone-methide tautomer intermediate, while the positively charged Arg554, in collaboration with the negatively charged Asp396, might stabilize this intermediate and form a hydrogen bonding network with the N(5)/O(4) region, thereby facilitating efficient FAD modification.
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Affiliation(s)
- Daiju Doubayashi
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, Fukuishi, Japan
| | - Masaya Oki
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, Fukuishi, Japan
| | - Bunzo Mikami
- Division of Agronomy and Horticultural Science, Graduate School of Agriculture, Kyoto University, Ujishi, Japan
| | - Hiroyuki Uchida
- Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, University of Fukui, Fukuishi, Japan
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9
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Özkılıç Y, Tüzün NŞ. Mechanism of Kynurenine 3-Monooxygenase-Catalyzed Hydroxylation Reaction: A Quantum Cluster Approach. J Phys Chem A 2019; 123:3149-3159. [PMID: 30888816 DOI: 10.1021/acs.jpca.8b11831] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The mechanism of the hydroxylation reaction between l-Kyn and model flavin adenine dinucleotide (FAD)-hydroperoxide was investigated via density functional theory (DFT) calculations in the absence and in the presence of the kynurenine 3-monooxygenase (KMO) enzyme by considering possible pathways that can lead to the product 3-hydroxykynurenine (3-HK). Crystal structure (pdb code: 5NAK )-based calculations involved a quantum cluster model in which the active site of the enzyme with the substrate l-Kyn was represented with 348 atoms. According to the deduced mechanism, KMO-catalyzed hydroxylation reaction takes place with four transformations. In the initial transition state, FAD delivers its peroxy hydroxyl to the l-Kyn ring, creating an sp3-hybridized carbon center. Then, the hydrogen on the hydroxyl moiety is immediately transferred back to the proximal oxygen that remained on FAD. These consequent transformations are in line with the somersault rearrangement previously described for similar enzymatic systems. The second step corresponds to a hydride shift from the sp3-hybridized carbon of the substrate ring to its adjacent carbon, producing the keto form of 3-HK. Then, keto-3-HK is transformed into its enol form (3-HK) with a water-assisted tautomerization. Lastly, FAD is oxidized with a water-assisted dehydration, which also involves 3-HK as a catalyst. In the proposed pathway, Asn54, Pro318, and a crystal water molecule were seen to play significant roles in the proton relays. The energies obtained via the cluster approach were calculated at the B3LYP/6-311+G(2d,2p)//B3LYP/6-31G(d,p) level with solvation (polarizable continuum model) and dispersion (DFT-D3(BJ)) corrections.
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Affiliation(s)
- Yılmaz Özkılıç
- Department of Chemistry, Faculty of Science and Letters , Istanbul Technical University , Maslak, Istanbul 34469 , Turkey
| | - Nurcan Ş Tüzün
- Department of Chemistry, Faculty of Science and Letters , Istanbul Technical University , Maslak, Istanbul 34469 , Turkey
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10
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Westphal AH, Tischler D, Heinke F, Hofmann S, Gröning JAD, Labudde D, van Berkel WJH. Pyridine Nucleotide Coenzyme Specificity of p-Hydroxybenzoate Hydroxylase and Related Flavoprotein Monooxygenases. Front Microbiol 2018; 9:3050. [PMID: 30631308 PMCID: PMC6315137 DOI: 10.3389/fmicb.2018.03050] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 11/27/2018] [Indexed: 12/03/2022] Open
Abstract
p-Hydroxybenzoate hydroxylase (PHBH; EC 1.14.13.2) is a microbial group A flavoprotein monooxygenase that catalyzes the ortho-hydroxylation of 4-hydroxybenzoate to 3,4-dihydroxybenzoate with the stoichiometric consumption of NAD(P)H and oxygen. PHBH and related enzymes lack a canonical NAD(P)H-binding domain and the way they interact with the pyridine nucleotide coenzyme has remained a conundrum. Previously, we identified a surface exposed protein segment of PHBH from Pseudomonas fluorescens involved in NADPH binding. Here, we report the first amino acid sequences of NADH-preferring PHBHs and a phylogenetic analysis of putative PHBHs identified in currently available bacterial genomes. It was found that PHBHs group into three clades consisting of NADPH-specific, NAD(P)H-dependent and NADH-preferring enzymes. The latter proteins frequently occur in Actinobacteria. To validate the results, we produced several putative PHBHs in Escherichia coli and confirmed their predicted coenzyme preferences. Based on phylogeny, protein energy profiling and lifestyle of PHBH harboring bacteria we propose that the pyridine nucleotide coenzyme specificity of PHBH emerged through adaptive evolution and that the NADH-preferring enzymes are the older versions of PHBH. Structural comparison and distance tree analysis of group A flavoprotein monooxygenases indicated that a similar protein segment as being responsible for the pyridine nucleotide coenzyme specificity of PHBH is involved in determining the pyridine nucleotide coenzyme specificity of the other group A members.
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Affiliation(s)
- Adrie H Westphal
- Laboratory of Biochemistry, Wageningen University and Research, Wageningen, Netherlands
| | - Dirk Tischler
- Interdisziplinäres Ökologisches Zentrum, Technische Universität Bergakademie Freiberg, Freiberg, Germany
| | - Florian Heinke
- Bioinformatics Group Mittweida, University of Applied Sciences Mittweida, Mittweida, Germany
| | - Sarah Hofmann
- Interdisziplinäres Ökologisches Zentrum, Technische Universität Bergakademie Freiberg, Freiberg, Germany
| | - Janosch A D Gröning
- Interdisziplinäres Ökologisches Zentrum, Technische Universität Bergakademie Freiberg, Freiberg, Germany
| | - Dirk Labudde
- Bioinformatics Group Mittweida, University of Applied Sciences Mittweida, Mittweida, Germany
| | - Willem J H van Berkel
- Laboratory of Biochemistry, Wageningen University and Research, Wageningen, Netherlands
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11
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Nguyen QT, Romero E, Dijkman WP, de Vasconcellos SP, Binda C, Mattevi A, Fraaije MW. Structure-Based Engineering of Phanerochaete chrysosporium Alcohol Oxidase for Enhanced Oxidative Power toward Glycerol. Biochemistry 2018; 57:6209-6218. [PMID: 30272958 PMCID: PMC6210165 DOI: 10.1021/acs.biochem.8b00918] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Glycerol
is a major byproduct of biodiesel production, and enzymes
that oxidize this compound have been long sought after. The recently
described alcohol oxidase from the white-rot basidiomycete Phanerochaete chrysosporium (PcAOX) was reported to feature
very mild activity on glycerol. Here, we describe the comprehensive
structural and biochemical characterization of this enzyme. PcAOX
was expressed in Escherichia coli in high yields
and displayed high thermostability. Steady-state kinetics revealed
that PcAOX is highly active toward methanol, ethanol, and 1-propanol
(kcat = 18, 19, and 11 s–1, respectively), but showed very limited activity toward glycerol
(kobs = 0.2 s–1 at 2
M substrate). The crystal structure of the homo-octameric PcAOX was
determined at a resolution of 2.6 Å. The catalytic center is
a remarkable solvent-inaccessible cavity located at the re side of the flavin cofactor. Its small size explains the observed
preference for methanol and ethanol as best substrates. These findings
led us to design several cavity-enlarging mutants with significantly
improved activity toward glycerol. Among them, the F101S variant had
a high kcat value of 3 s–1, retaining a high degree of thermostability. The crystal structure
of F101S PcAOX was solved, confirming the site of mutation and the
larger substrate-binding pocket. Our data demonstrate that PcAOX is
a very promising enzyme for glycerol biotransformation.
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Affiliation(s)
- Quoc-Thai Nguyen
- Molecular Enzymology Group, Groningen Biomolecular Sciences and Biotechnology Institute , University of Groningen , Nijenborgh 4 , 9747 AG Groningen , The Netherlands.,Scuola Universitaria Superiore IUSS Pavia , Piazza della Vittoria 15 , 27100 Pavia , Italy.,Faculty of Pharmacy , University of Medicine and Pharmacy at Ho Chi Minh City , 41 Dinh Tien Hoang Street, Ben Nghe Ward, District 1 , Ho Chi Minh City , Vietnam
| | - Elvira Romero
- Molecular Enzymology Group, Groningen Biomolecular Sciences and Biotechnology Institute , University of Groningen , Nijenborgh 4 , 9747 AG Groningen , The Netherlands
| | - Willem P Dijkman
- Molecular Enzymology Group, Groningen Biomolecular Sciences and Biotechnology Institute , University of Groningen , Nijenborgh 4 , 9747 AG Groningen , The Netherlands
| | - Suzan Pantaroto de Vasconcellos
- Molecular Enzymology Group, Groningen Biomolecular Sciences and Biotechnology Institute , University of Groningen , Nijenborgh 4 , 9747 AG Groningen , The Netherlands.,Department of Biological Science , Federal University of São Paulo (UNIFESP) , Diadema , SP 09913-030 , Brazil
| | - Claudia Binda
- Department of Biology and Biotechnology , University of Pavia , Via Ferrata 1 , 27100 Pavia , Italy
| | - Andrea Mattevi
- Department of Biology and Biotechnology , University of Pavia , Via Ferrata 1 , 27100 Pavia , Italy
| | - Marco W Fraaije
- Molecular Enzymology Group, Groningen Biomolecular Sciences and Biotechnology Institute , University of Groningen , Nijenborgh 4 , 9747 AG Groningen , The Netherlands
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12
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Kim HT, Na BK, Chung J, Kim S, Kwon SK, Cha H, Son J, Cho JM, Hwang KY. Structural Basis for Inhibitor-Induced Hydrogen Peroxide Production by Kynurenine 3-Monooxygenase. Cell Chem Biol 2018; 25:426-438.e4. [PMID: 29429898 DOI: 10.1016/j.chembiol.2018.01.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 10/17/2017] [Accepted: 01/08/2018] [Indexed: 11/18/2022]
Abstract
Kynurenine 3-monooxygenase (KMO) inhibitors have been developed for the treatment of neurodegenerative disorders. The mechanisms of flavin reduction and hydrogen peroxide production by KMO inhibitors are unknown. Herein, we report the structure of human KMO and crystal structures of Saccharomyces cerevisiae (sc) and Pseudomonas fluorescens (pf) KMO with Ro 61-8048. Proton transfer in the hydrogen bond network triggers flavin reduction in p-hydroxybenzoate hydroxylase, but the mechanism triggering flavin reduction in KMO is different. Conformational changes via π-π interactions between the loop above the flavin and substrate or non-substrate effectors lead to disorder of the C-terminal α helix in scKMO and shifts of domain III in pfKMO, stimulating flavin reduction. Interestingly, Ro 61-8048 has two different binding modes. It acts as a competitive inhibitor in scKMO and as a non-substrate effector in pfKMO. These findings provide understanding of the catalytic cycle of KMO and insight for structure-based drug design of KMO inhibitors.
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Affiliation(s)
- Hyun Tae Kim
- Crystalgenomics, Inc., 5F, Tower A, Korea Bio Park 700, Daewangpangyo-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 13524, Korea; Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Korea
| | - Byeong Kwan Na
- Crystalgenomics, Inc., 5F, Tower A, Korea Bio Park 700, Daewangpangyo-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 13524, Korea
| | - Jiwoung Chung
- Crystalgenomics, Inc., 5F, Tower A, Korea Bio Park 700, Daewangpangyo-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 13524, Korea
| | - Sulhee Kim
- Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Korea
| | - Sool Ki Kwon
- Crystalgenomics, Inc., 5F, Tower A, Korea Bio Park 700, Daewangpangyo-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 13524, Korea
| | - Hyunju Cha
- Crystalgenomics, Inc., 5F, Tower A, Korea Bio Park 700, Daewangpangyo-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 13524, Korea
| | - Jonghyeon Son
- Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Korea
| | - Joong Myung Cho
- Crystalgenomics, Inc., 5F, Tower A, Korea Bio Park 700, Daewangpangyo-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 13524, Korea.
| | - Kwang Yeon Hwang
- Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Korea.
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13
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Robbins JM, Souffrant MG, Hamelberg D, Gadda G, Bommarius AS. Enzyme-Mediated Conversion of Flavin Adenine Dinucleotide (FAD) to 8-Formyl FAD in Formate Oxidase Results in a Modified Cofactor with Enhanced Catalytic Properties. Biochemistry 2017. [PMID: 28640638 DOI: 10.1021/acs.biochem.7b00335] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Flavins, including flavin adenine dinucleotide (FAD), are fundamental catalytic cofactors that are responsible for the redox functionality of a diverse set of proteins. Alternatively, modified flavin analogues are rarely found in nature as their incorporation typically results in inactivation of flavoproteins, thus leading to the disruption of important cellular pathways. Here, we report that the fungal flavoenzyme formate oxidase (FOX) catalyzes the slow conversion of noncovalently bound FAD to 8-formyl FAD and that this conversion results in a nearly 10-fold increase in formate oxidase activity. Although the presence of an enzyme-bound 8-formyl FMN has been reported previously as a result of site-directed mutagenesis studies of lactate oxidase, FOX is the first reported case of 8-formyl FAD in a wild-type enzyme. Therefore, the formation of the 8-formyl FAD cofactor in formate oxidase was investigated using steady-state kinetics, site-directed mutagenesis, ultraviolet-visible, circular dichroism, and fluorescence spectroscopy, liquid chromatography with mass spectrometry, and computational analysis. Surprisingly, the results from these studies indicate not only that 8-formyl FAD forms spontaneously and results in the active form of FOX but also that its autocatalytic formation is dependent on a nearby arginine residue, R87. Thus, this work describes a new enzyme cofactor and provides insight into the little-understood mechanism of enzyme-mediated 8α-flavin modifications.
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Affiliation(s)
- John M Robbins
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332-0100, United States.,Engineered Biosystems Building (EBB), Georgia Institute of Technology , Atlanta, Georgia 30332-2000, United States
| | - Michael G Souffrant
- Department of Chemistry, Georgia State University , Atlanta, Georgia 30302-3965, United States.,Center for Diagnostics and Therapeutics, Georgia State University , Atlanta, Georgia 30302-3965, United States.,Molecular Basis of Disease Program, Georgia State University , Atlanta, Georgia 30303, United States
| | - Donald Hamelberg
- Department of Chemistry, Georgia State University , Atlanta, Georgia 30302-3965, United States.,Center for Diagnostics and Therapeutics, Georgia State University , Atlanta, Georgia 30302-3965, United States.,Molecular Basis of Disease Program, Georgia State University , Atlanta, Georgia 30303, United States
| | - Giovanni Gadda
- Department of Chemistry, Georgia State University , Atlanta, Georgia 30302-3965, United States.,Center for Diagnostics and Therapeutics, Georgia State University , Atlanta, Georgia 30302-3965, United States.,Center for Biotechnology and Drug Design, Georgia State University , Atlanta, Georgia 30302-3965, United States.,Department of Biology, Georgia State University , Atlanta, Georgia 30302-3965, United States
| | - Andreas S Bommarius
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332-0100, United States.,Engineered Biosystems Building (EBB), Georgia Institute of Technology , Atlanta, Georgia 30332-2000, United States.,School of Chemistry and Biochemistry, Georgia Institute of Technology , Atlanta, Georgia 30332-0400, United States
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14
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Kanteev M, Bregman-Cohen A, Deri B, Shahar A, Adir N, Fishman A. A crystal structure of 2-hydroxybiphenyl 3-monooxygenase with bound substrate provides insights into the enzymatic mechanism. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:1906-1913. [PMID: 26275805 DOI: 10.1016/j.bbapap.2015.08.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 08/06/2015] [Accepted: 08/09/2015] [Indexed: 11/16/2022]
Abstract
2-Hydroxybiphenyl 3-monooxygenase (HbpA) is an FAD dependent monooxygenase which catalyzes the ortho-hydroxylation of a broad range of 2-substituted phenols in the presence of NADH and molecular oxygen. We have determined the structure of HbpA from the soil bacterium Pseudomonas azelaica HBP1 with bound 2-hydroxybiphenyl, as well as several variants, at a resolution of 2.3-2.5Å to investigate structure function correlations of the enzyme. An observed hydrogen bond between 2-hydroxybiphenyl and His48 in the active site confirmed the previously suggested role of this residue in substrate deprotonation. The entrance to the active site was confirmed by generating variant G255F which exhibited only 7% of the wild-type's specific activity of product formation, suggesting inhibition of substrate entrance into the active site by the large aromatic residue. Residue Arg242 is suggested to facilitate FAD movement and reduction as was previously reported in studies on the homologous protein para-hydroxybenzoate hydroxylase. In addition, it is suggested that Trp225, which is located in the active site, facilitates proper substrate entrance into the binding pocket in contrast to aklavinone-11-hydroxylase and para-hydroxybenzoate hydroxylase in which a residue at a similar position is responsible for substrate deprotonation. Structure function correlations described in this work will aid in the design of variants with improved activity and altered selectivity for potential industrial applications.
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Affiliation(s)
- Margarita Kanteev
- Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa, Israel
| | - Almog Bregman-Cohen
- Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa, Israel
| | - Batel Deri
- Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa, Israel
| | - Anat Shahar
- Macromolecular Crystallography Research Center (MCRC), Department of Life Sciences & NIBN, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Noam Adir
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa, Israel
| | - Ayelet Fishman
- Department of Biotechnology and Food Engineering, Technion-Israel Institute of Technology, Haifa, Israel.
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15
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Minami A, Oguri H, Watanabe K, Oikawa H. Biosynthetic machinery of ionophore polyether lasalocid: enzymatic construction of polyether skeleton. Curr Opin Chem Biol 2013; 17:555-61. [DOI: 10.1016/j.cbpa.2013.06.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 05/29/2013] [Accepted: 06/01/2013] [Indexed: 02/02/2023]
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16
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Minami A, Shimaya M, Suzuki G, Migita A, Shinde SS, Sato K, Watanabe K, Tamura T, Oguri H, Oikawa H. Sequential enzymatic epoxidation involved in polyether lasalocid biosynthesis. J Am Chem Soc 2012; 134:7246-9. [PMID: 22506807 DOI: 10.1021/ja301386g] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Enantioselective epoxidation followed by regioselective epoxide opening reaction are the key processes in construction of the polyether skeleton. Recent genetic analysis of ionophore polyether biosynthetic gene clusters suggested that flavin-containing monooxygenases (FMOs) could be involved in the oxidation steps. In vivo and in vitro analyses of Lsd18, an FMO involved in the biosynthesis of polyether lasalocid, using simple olefin or truncated diene of a putative substrate as substrate mimics demonstrated that enantioselective epoxidation affords natural type mono- or bis-epoxide in a stepwise manner. These findings allow us to figure out enzymatic polyether construction in lasalocid biosynthesis.
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Affiliation(s)
- Atsushi Minami
- Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan
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17
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Bach RD. Role of the Somersault Rearrangement in the Oxidation Step for Flavin Monooxygenases (FMO). A Comparison between FMO and Conventional Xenobiotic Oxidation with Hydroperoxides. J Phys Chem A 2011; 115:11087-100. [DOI: 10.1021/jp208087u] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Robert D. Bach
- Department of Chemistry and Biochemistry, University of Delaware, Delaware, United States
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18
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Montersino S, Tischler D, Gassner GT, van Berkel WJH. Catalytic and Structural Features of Flavoprotein Hydroxylases and Epoxidases. Adv Synth Catal 2011. [DOI: 10.1002/adsc.201100384] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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19
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Volkers G, Palm GJ, Weiss MS, Wright GD, Hinrichs W. Structural basis for a new tetracycline resistance mechanism relying on the TetX monooxygenase. FEBS Lett 2011; 585:1061-6. [PMID: 21402075 DOI: 10.1016/j.febslet.2011.03.012] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Accepted: 03/04/2011] [Indexed: 11/30/2022]
Abstract
The flavin-dependent monooxygenase TetX confers resistance to all clinically relevant tetracyclines, including the recently approved, broad-spectrum antibiotic tigecycline (Tygacil®) which is a critical last-ditch defense against multidrug-resistant pathogens. TetX represents the first resistance mechanism against tigecycline, which circumvents both the tet-gene encoded resistances, relying on active efflux of tetracyclines, and ribosomal protection proteins. The alternative enzyme-based mechanism of TetX depends on regioselective hydroxylation of tetracycline antibiotics to 11a-hydroxy-tetracyclines. Here, we report the X-ray crystallographic structure determinations at 2.1Å resolution of native TetX from Bacteroides thetaiotaomicron and its complexes with tetracyclines. Our crystal structures explain the extremely versatile substrate diversity of the enzyme and provide a first step towards the rational design of novel tetracycline derivatives to counter TetX-based resistance prior to emerging clinical observations.
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Affiliation(s)
- Gesa Volkers
- Institut für Biochemie, Universität Greifswald, Greifswald, Germany
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20
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Control of catalysis in flavin-dependent monooxygenases. Arch Biochem Biophys 2010; 493:26-36. [DOI: 10.1016/j.abb.2009.11.028] [Citation(s) in RCA: 129] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2009] [Revised: 11/17/2009] [Accepted: 11/17/2009] [Indexed: 11/17/2022]
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21
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Tabacchi G, Zucchini D, Caprini G, Gamba A, Lederer F, Vanoni MA, Fois E. L-lactate dehydrogenation in flavocytochrome b2: a first principles molecular dynamics study. FEBS J 2009; 276:2368-80. [PMID: 19348008 DOI: 10.1111/j.1742-4658.2009.06969.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
First principles molecular dynamics studies on active-site models of flavocytochrome b2 (L-lactate : cytochrome c oxidoreductase, Fcb2), in complex with the substrate, were carried out for the first time to contribute towards establishing the mechanism of the enzyme-catalyzed L-lactate oxidation reaction, a still-debated issue. In the calculated enzyme-substrate model complex, the L-lactate alpha-OH hydrogen is hydrogen bonded to the active-site base H373 Nepsilon, whereas the Halpha is directed towards flavin N5, suggesting that the reaction is initiated by alpha-OH proton abstraction. Starting from this structure, simulation of L-lactate oxidation led to formation of the reduced enzyme-pyruvate complex by transfer of a hydride from lactate to flavin mononucleotide, without intermediates, but with alpha-OH proton abstraction preceding Halpha transfer and a calculated free energy barrier (12.1 kcal mol(-1)) consistent with that determined experimentally (13.5 kcal mol(-1)). Simulation results also revealed features that are of relevance to the understanding of catalysis in Fcb2 homologs and in a number of flavoenzymes. Namely, they highlighted the role of: (a) the flavin mononucleotide-ribityl chain 2'OH group in maintaining the conserved K349 in a geometry favoring flavin reduction; (b) an active site water molecule belonging to a S371-Wat-D282-H373 hydrogen-bonded chain, conserved in the structures of Fcb2 family members, which modulates the reactivity of the key catalytic histidine; and (c) the flavin C4a-C10a locus in facilitating proton transfer from the substrate to the active-site base, favoring the initial step of the lactate dehydrogenation reaction.
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Affiliation(s)
- Gloria Tabacchi
- Dipartimento di Scienze Chimiche ed Ambientali and INSTM, Università dell'Insubria, Como, Italy
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22
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Fruk L, Kuo CH, Torres E, Niemeyer CM. Apoenzyme reconstitution as a chemical tool for structural enzymology and biotechnology. Angew Chem Int Ed Engl 2009; 48:1550-74. [PMID: 19165853 DOI: 10.1002/anie.200803098] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Many enzymes contain a nondiffusible organic cofactor, often termed a prosthetic group, which is located in the active site and essential for the catalytic activity of the enzyme. These cofactors can often be extracted from the protein to yield the respective apoenzyme, which can subsequently be reconstituted with an artificial analogue of the native cofactor. Nowadays a large variety of synthetic cofactors can be used for the reconstitution of apoenzymes and, thus, generate novel semisynthetic enzymes. This approach has been refined over the past decades to become a versatile tool of structural enzymology to elucidate structure-function relationships of enzymes. Moreover, the reconstitution of apoenzymes can also be used to generate enzymes possessing enhanced or even entirely new functionality. This Review gives an overview on historical developments and the current state-of-the-art on apoenzyme reconstitution.
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Affiliation(s)
- Ljiljana Fruk
- Universität Dortmund, Fachbereich Chemie, Biologisch-Chemische Mikrostrukturtechnik, Otto-Hahn Strasse 6, 44227 Dortmund, Germany.
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23
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Fruk L, Kuo CH, Torres E, Niemeyer C. Rekonstitution von Apoenzymen als chemisches Werkzeug für die strukturelle Enzymologie und Biotechnologie. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200803098] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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24
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Kudryashova EV, Visser AJWG, van Berkel WJH. Monomer formation and function of p-hydroxybenzoate hydroxylase in reverse micelles and in dimethylsulfoxide/water mixtures. Chembiochem 2008; 9:413-9. [PMID: 18176933 DOI: 10.1002/cbic.200700267] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
It has previously been postulated that the dimeric form of the flavoprotein p-hydroxybenzoate hydroxylase (PHBH) is important for catalysis. Here it is demonstrated that the monomeric form of PHBH is active. In a water/AOT/isooctane reverse micellar system, the function of the monomeric and dimeric forms of PHBH could be observed separately by varying the size of the micelles. A considerable decrease in the K(M) value for p-hydroxybenzoate (POHB) was found for monomeric PHBH, accompanied by a 1.5-fold decrease in enzymatic activity. The same tendency was observed when monomers of PHBH were formed by adding DMSO to the buffer. The FAD in PHBH and PHBH labeled with the fluorescence dye Alexa488 was investigated by time-resolved fluorescence anisotropy to observe monomer formation in water/DMSO mixtures. Monomer formation of PHBH occurred gradually with increasing DMSO content in the mixture. Pure PHBH monomers were detected at DMSO concentrations of 30 % (v/v) and higher.
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Affiliation(s)
- Elena V Kudryashova
- Laboratory of Biochemistry, Wageningen University, Wageningen, The Netherlands
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25
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Time-resolved fluorescence analysis of the mobile flavin cofactor in p-hydroxybenzoate hydroxylase. J CHEM SCI 2007. [DOI: 10.1007/s12039-007-0019-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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26
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Westphal AH, Matorin A, Hink MA, Borst JW, van Berkel WJH, Visser AJWG. Real-time enzyme dynamics illustrated with fluorescence spectroscopy of p-hydroxybenzoate hydroxylase. J Biol Chem 2006; 281:11074-81. [PMID: 16492664 DOI: 10.1074/jbc.m600609200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have used the flavoenzyme p-hydroxybenzoate hydroxylase (PHBH) to illustrate that a strongly fluorescent donor label can communicate with the flavin via single-pair Förster resonance energy transfer (spFRET). The accessible Cys-116 of PHBH was labeled with two different fluorescent maleimides with full preservation of enzymatic activity. One of these labels shows overlap between its fluorescence spectrum and the absorption spectrum of the FAD prosthetic group in the oxidized state, while the other fluorescent probe does not have this spectral overlap. The spectral overlap strongly diminished when the flavin becomes reduced during catalysis. The donor fluorescence properties can then be used as a sensitive antenna for the flavin redox state. Time-resolved fluorescence experiments on ensembles of labeled PHBH molecules were carried out in the absence and presence of enzymatic turnover. Distinct changes in fluorescence decays of spFRET-active PHBH can be observed when the enzyme is performing catalysis using both substrates p-hydroxybenzoate and NADPH. Single-molecule fluorescence correlation spectroscopy on spFRET-active PHBH showed the presence of a relaxation process (relaxation time of 23 micros) that is related to catalysis. In addition, in both labeled PHBH preparations the number of enzyme molecules reversibly increased during enzymatic turnover indicating that the dimer-monomer equilibrium is affected.
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Affiliation(s)
- Adrie H Westphal
- Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands
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27
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Ozimek P, Veenhuis M, van der Klei IJ. Alcohol oxidase: a complex peroxisomal, oligomeric flavoprotein. FEMS Yeast Res 2005; 5:975-83. [PMID: 16169288 DOI: 10.1016/j.femsyr.2005.06.005] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2005] [Revised: 06/07/2005] [Accepted: 06/07/2005] [Indexed: 10/25/2022] Open
Abstract
Alcohol oxidase (AO) is the key enzyme of methanol metabolism in methylotrophic yeast species. It catalyses the first step of methanol catabolism, namely its oxidation to formaldehyde with concomitant production of hydrogen peroxide. In its mature active form, AO is a molecule of high molecular mass (600 kDa) that consists of eight identical subunits, each of which carry one non-covalently bound flavin adenine nucleotide (FAD) molecule as the prosthetic group. In vivo, the protein is compartmentalized into special cell organelles, termed peroxisomes. AO is an abundant protein and its synthesis is strictly regulated by repression/derepression and induction mechanisms that occur at the transcriptional level. Various aspects of its sorting and assembly/activation render AO a unique protein. Recent developments of AO synthesis, sorting and assembly/activation are highlighted in this paper.
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Affiliation(s)
- Paulina Ozimek
- Eukaryotic Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, P.O. Box 14, 9750 AA Haren, The Netherlands
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28
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Entsch B, Cole LJ, Ballou DP. Protein dynamics and electrostatics in the function of p-hydroxybenzoate hydroxylase. Arch Biochem Biophys 2005; 433:297-311. [PMID: 15581585 DOI: 10.1016/j.abb.2004.09.029] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2004] [Indexed: 11/18/2022]
Abstract
para-Hydroxybenzoate hydroxylase is a flavoprotein monooxygenase that catalyzes a reaction in two parts: reduction of the enzyme cofactor, FAD, by NADPH in response to binding p-hydroxybenzoate to the enzyme, then oxidation of reduced FAD by oxygen to form a hydroperoxide, which oxygenates p-hydroxybenzoate to form 3,4-dihydroxybenzoate. These diverse reactions all occur within a single polypeptide and are achieved through conformational rearrangements of the isoalloxazine ring and protein residues within the protein structure. In this review, we examine the complex dynamic behavior of the protein that enables regulated fast and specific catalysis to occur. Original research papers (principally from the past 15 years) provide the information that is used to develop a comprehensive overview of the catalytic process. Much of this information has come from detailed analysis of many specific mutants of the enzyme using rapid reaction technology, biophysical measurements, and high-resolution structures obtained by X-ray crystallography. We describe how three conformations of the enzyme provide a foundation for the catalytic cycle. One conformation has a closed active site for the conduct of the oxygen reactions, which must occur in the absence of solvent. The second conformation has a partly open active site for exchange of substrate and product, and the third conformation has a closed protein structure with the isoalloxazine ring rotated out to the surface for reaction with NADPH, which binds in a surface cleft. A fundamental feature of the enzyme is a H-bond network that connects the phenolic group of the substrate in the buried active site to the surface of the protein. This network serves to protonate and deprotonate the substrate and product in the active site to promote catalysis and regulate the coordination of conformational states for efficient catalysis.
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Affiliation(s)
- Barrie Entsch
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109-0606, USA
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29
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Bach RD, Dmitrenko O. Model Studies onp-Hydroxybenzoate Hydroxylase. The Catalytic Role of Arg-214 and Tyr-201 in the Hydroxylation Step. J Am Chem Soc 2004; 126:127-42. [PMID: 14709077 DOI: 10.1021/ja036310+] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A model C-(4a)-flavinhydroperoxide (FlHOOH) is described that contains the tricyclic isoalloxazine moiety, the C-4a-hydroperoxide functionality, and a beta-hydroxyethyl group to model the effect of the 2'-OH group of the ribityl side chain of native FADHOOH. The electronic structures of this reduced flavin (H(3)()Fl(red)()), its N1 anion (H(2)()Fl(red)()(-)()), oxidized flavin (HFl(ox)()), and FlHOOH have been fully optimized at the B3LYP/ 6-31+G(d,p) level of theory. This model C-4a-flavinhydroperoxide is used to describe the transition state for the key step in the paradigm aromatic hydroxylase, p-hydroxybenzoate hydroxylase (PHBH): the oxidation of p-hydroxybenzoate (p-OHB). The Tyrosine-201 residue in PHBH is modeled by phenol, and Arginine-214 is modeled by guanidine. Electrophilic aromatic substitution proceeds by an S(N)2-like attack of the aromatic sextet of p-OHB phenolate anion on the distal oxygen of FlHOOH 3. The transition structure for oxygen atom transfer is fully optimized [B3LYP/6-31+G(d,p)] and has a classical activation barrier of 24.9 kcal/mol. These data suggest that the role of the Tyr-201 is to orient the p-OHB substrate and to properly align it for the oxygen transfer step. Although the negatively charged phenolate oxygen does activate the C-3 carbon of p-OHB phenolate anion toward oxidation relative to ortho oxidation of the carboxylate anion, it appears that H-bonding the Tyr-201 residue to this phenolic oxygen stabilizes both the ground state (GS) and the transition state (TS) approximately equally and therefore plays only a minor role, if any, in lowering the activation barrier. Complexation of p-OHB with guanidine has only a modest effect upon the oxidation barriers. When the complex is in the form of a salt-bridge (10a), the barrier is only slightly reduced. When the TSs are placed in THF solvent (COSMO) with full geometry optimization, salt-bridge TS-A is slightly favored (DeltaDeltaE() = 2.3 kcal/mol).
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Affiliation(s)
- Robert D Bach
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA
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30
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Bach RD, Dmitrenko O. Electronic Requirements for Oxygen Atom Transfer from Alkyl Hydroperoxides. Model Studies on Multisubstrate Flavin-Containing Monooxygenases. J Phys Chem B 2003. [DOI: 10.1021/jp035289w] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Robert D. Bach
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
| | - Olga Dmitrenko
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
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31
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Abstract
Flavoproteins are ubiquitous redox proteins that are involved in many biological processes. In the majority of flavoproteins, the flavin cofactor is tightly but noncovalently bound. Reversible dissociation of flavoproteins into apoprotein and flavin prosthetic group yields valuable insights in flavoprotein folding, function and mechanism. Replacement of the natural cofactor with artificial flavins has proved to be especially useful for the determination of the solvent accessibility, polarity, reaction stereochemistry and dynamic behaviour of flavoprotein active sites. In this review we summarize the advances made in the field of flavoprotein deflavination and reconstitution. Several sophisticated chromatographic procedures to either deflavinate or reconstitute the flavoprotein on a large scale are discussed. In a subset of flavoproteins, the flavin cofactor is covalently attached to the polypeptide chain. Studies from riboflavin-deficient expression systems and site-directed mutagenesis suggest that the flavinylation reaction is a post-translational, rather than a cotranslational, process. These genetic approaches have also provided insight into the mechanism of covalent flavinylation and the rationale for this atypical protein modification.
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Affiliation(s)
- Marco H Hefti
- Laboratory of Biochemistry, Wageningen University, The Netherlands
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32
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Palfey BA, Murthy YVSN, Massey V. Altered balance of half-reactions in p-hydroxybenzoate hydroxylase caused by substituting the 2'-carbon of FAD with fluorine. J Biol Chem 2003; 278:22210-6. [PMID: 12684497 DOI: 10.1074/jbc.m301830200] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Apo-p-hydroxybenzoate hydroxylase was reconstituted using 2'-fluoro-2'-deoxy-arabino-FAD, a synthetic flavin in which the hydroxyl of the 2'-center of the ribityl chain was replaced with fluorine in an inverted configuration. The absorbance spectral changes caused by the binding of either p-hydroxybenzoate (pOHB) or 2,4-dihydroxybenzoate (2,4-diOHB) indicated that the isoalloxazine of the artificial flavin adopts the more solvent-exposed "out" conformation rather than the partially buried "in" conformation near the aromatic substrate. In contrast, the flavin of the natural enzyme adopts the in conformation when pOHB is bound. Much of the behavior of the artificial enzyme can be rationalized in light of the preference of the flavin for the out conformation, including the weaker binding of pOHB, the tighter binding of 2,4-diOHB, and the slower reactions involved in the hydroxylation of pOHB and 2,4-diOHB. Particularly noteworthy is the enhancement of the reduction of the flavin by NADPH when pOHB is bound to the active site, consistent with the recent finding that the reaction occurs when the flavin adopts the out conformation (Palfey, B. A., Moran, G. R., Entsch, B., Ballou, D. P., and Massey, V. (1999) Biochemistry 38, 1153-1158). Thus, whereas the change that induces the out conformation is detrimental to the oxidative half-reaction, it improves the reductive half-reaction, showing that the control of the flavin position in p-hydroxybenzoate hydroxylase represents a compromise between the conflicting needs of two chemically disparate half-reactions, and demonstrating that the 2'-hydroxyl of FAD can serve as a critical control element in flavoenzyme catalysis.
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Affiliation(s)
- Bruce A Palfey
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0606, USA.
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33
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Hefti MH, Milder FJ, Boeren S, Vervoort J, van Berkel WJH. A His-tag based immobilization method for the preparation and reconstitution of apoflavoproteins. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1619:139-43. [PMID: 12527109 DOI: 10.1016/s0304-4165(02)00474-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The NifL PAS domain from Azotobacter vinelandii is a flavoprotein with FAD as the prosthetic group. Here we describe a novel immobilization procedure for the large-scale preparation of apo NifL PAS domain and its efficient reconstitution with either 2,4a-13C-FAD or 2,4a-13C-FMN. In this procedure, the His-tagged holoprotein is bound to an immobilized metal affinity column and the flavin is released by washing the column with buffer containing 2 M KBr and 2 M urea. The apoprotein is reconstituted on-column with the (artificial) flavin cofactor, and then eluted with buffer containing 250 mM imidazole. Alternatively, the immobilized apoprotein can be released from the column matrix before reconstitution. The His-tag based immobilization method of preparing reconstituted (or apo) NifL PAS domain protein has the advantage that it combines a protein affinity chromatography technique with limited protein loss, resulting in a high protein yield with extremely efficient flavin reconstitution. This on-column reconstitution method can also be used in cases where the apoprotein is unstable. Therefore, it may develop as a universal method for replacement of flavin or other cofactors.
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Affiliation(s)
- Marco H Hefti
- Laboratory of Biochemistry, Department of Agrotechnology and Food Sciences, Wageningen University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands.
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34
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Moonen M, Fraaije M, Rietjens I, Laane C, van Berkel W. Flavoenzyme-Catalyzed Oxygenations and Oxidations of Phenolic Compounds. Adv Synth Catal 2002. [DOI: 10.1002/1615-4169(200212)344:10<1023::aid-adsc1023>3.0.co;2-t] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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35
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36
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Tahallah N, Van Den Heuvel RHH, Van Den Berg WAM, Maier CS, Van Berkel WJH, Heck AJR. Cofactor-dependent assembly of the flavoenzyme vanillyl-alcohol oxidase. J Biol Chem 2002; 277:36425-32. [PMID: 12107187 DOI: 10.1074/jbc.m205841200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The oligomerization of the flavoprotein vanillyl-alcohol oxidase (VAO) and its site-directed mutant H61T was studied by mass spectrometry. Native VAO has a covalently bound FAD and forms primarily octameric assemblies of 507 kDa. H61T is purified as a FAD-free apoprotein and mainly exists as a dimeric species of 126 kDa. Binding of FAD to apoH61T rapidly restores enzyme activity and induces octamerization, although association of H61T dimers seems not to be crucial for enzyme activity. Reconstitution of H61T with the cofactor analog 5'-ADP also promotes octamerization. FMN on the other hand, interacts with apoH61T without stimulating dimer association. These results are in line with observations made for several other flavoenzymes, which contain a Rossmann fold. Members of the VAO flavoprotein family do not contain a Rossmann fold but do share two conserved loops that are responsible for binding the pyrophosphate moiety of FAD. Therefore, the observed FAD-induced oligomerization might be general for this family. We speculate that upon FAD binding, small conformational changes in the ADP-binding pocket of the dimeric VAO species are transmitted to the protein surface, promoting oligomerization.
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Affiliation(s)
- Nora Tahallah
- Department of Biomolecular Mass Spectrometry, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands
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37
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Wang J, Ortiz-Maldonado M, Entsch B, Massey V, Ballou D, Gatti DL. Protein and ligand dynamics in 4-hydroxybenzoate hydroxylase. Proc Natl Acad Sci U S A 2002; 99:608-13. [PMID: 11805318 PMCID: PMC117353 DOI: 10.1073/pnas.022640199] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
para-Hydroxybenzoate hydroxylase catalyzes a two-step reaction that demands precise control of solvent access to the catalytic site. The first step of the reaction, reduction of flavin by NADPH, requires access to solvent. The second step, oxygenation of reduced flavin to a flavin C4a-hydroperoxide that transfers the hydroxyl group to the substrate, requires that solvent be excluded to prevent breakdown of the hydroperoxide to oxidized flavin and hydrogen peroxide. These conflicting requirements are met by the coordination of multiple movements involving the protein, the two cofactors, and the substrate. Here, using the R220Q mutant form of para-hydroxybenzoate hydroxylase, we show that in the absence of substrate, the large beta alpha beta domain (residues 1-180) and the smaller sheet domain (residues 180-270) separate slightly, and the flavin swings out to a more exposed position to open an aqueous channel from the solvent to the protein interior. Substrate entry occurs by first binding at a surface site and then sliding into the protein interior. In our study of this mutant, the structure of the complex with pyridine nucleotide was obtained. This cofactor binds in an extended conformation at the enzyme surface in a groove that crosses the binding site of FAD. We postulate that for stereospecific reduction, the flavin swings to an out position and NADPH assumes a folded conformation that brings its nicotinamide moiety into close contact with the isoalloxazine moiety of the flavin. This work clearly shows how complex dynamics can play a central role in catalysis by enzymes.
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Affiliation(s)
- Jian Wang
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, MI 48201, USA
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38
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Altose MD, Zheng Y, Dong J, Palfey BA, Carey PR. Comparing protein-ligand interactions in solution and single crystals by Raman spectroscopy. Proc Natl Acad Sci U S A 2001; 98:3006-11. [PMID: 11248022 PMCID: PMC30597 DOI: 10.1073/pnas.061029598] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
By using a Raman microscope, we show that it is possible to probe the conformational states in protein crystals and crystal fragments under growth conditions (in hanging drops). The flavin cofactor in the enzyme para-hydroxybenzoate hydroxylase can assume two conformations: buried in the protein matrix ("in") or essentially solvent-exposed ("out"). By using Raman difference spectroscopy, we previously have identified characteristic flavin marker bands for the in and out conformers in the solution phase. Now we show that the flavin Raman bands can be used to probe these conformational states in crystals, permitting a comparison between solution and crystal environments. The in or out marker bands are similar for the respective conformers in the crystal and in solution; however, significant differences do exist, showing that the environments for the flavin's isoalloxazine ring are not identical in the two phases. Moreover, the Raman-band widths of the flavin modes are narrower for both in and out conformers in the crystals, indicating that the flavin exists in a more limited range of closely related conformational states in the crystal than in solution. In general, the ability to compare detailed Raman data for complexes in crystals and solution provides a means of bridging crystallographic and solution studies.
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Affiliation(s)
- M D Altose
- Department of Biochemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4935, USA
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39
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Eppink MH, Cammaart E, Van Wassenaar D, Middelhoven WJ, van Berkel WJ. Purification and properties of hydroquinone hydroxylase, a FAD-dependent monooxygenase involved in the catabolism of 4-hydroxybenzoate in Candida parapsilosis CBS604. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:6832-40. [PMID: 11082194 DOI: 10.1046/j.1432-1033.2000.01783.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The ascomycetous yeast Candida parapsilosis CBS604 catabolizes 4-hydroxybenzoate through the initial formation of hydroquinone (1, 4-dihydroxybenzene). High levels of hydroquinone hydroxylase activity are induced when the yeast is grown on either 4-hydroxybenzoate, 2,4-dihydroxybenzoate, 1,3-dihydroxybenzene or 1, 4-dihydroxybenzene as the sole carbon source. The monooxygenase constitutes up to 5% of the total amount of protein and is purified to apparent homogeneity in three chromatographic steps. Hydroquinone hydroxylase from C. parapsilosis is a homodimer of about 150 kDa with each 76-kDa subunit containing a tightly noncovalently bound FAD. The flavin prosthetic group is quantitatively resolved from the protein at neutral pH in the presence of chaotropic salts. The apoenzyme is dimeric and readily reconstituted with FAD. Hydroquinone hydroxylase from C. parapsilosis catalyzes the ortho-hydroxylation of a wide range of monocyclic phenols with the stoichiometric consumption of NADPH and oxygen. With most aromatic substrates, no uncoupling of hydroxylation occurs. Hydroxylation of monofluorinated phenols is highly regiospecific with a preference for C6 hydroxylation. Binding of phenol highly stimulates the rate of flavin reduction by NADPH. At pH 7.6, 25 degrees C, this step does not limit the rate of overall catalysis. During purification, hydroquinone hydroxylase is susceptible towards limited proteolysis. Proteolytic cleavage does not influence the enzyme dimeric nature but results in relatively stable protein fragments of 55, 43, 35 and 22 kDa. N-Terminal peptide sequence analysis revealed the presence of two nick sites and showed that hydroquinone hydroxylase from C. parapsilosis is structurally related to phenol hydroxylase from Trichosporon cutaneum. The implications of these findings for the catalytic mechanism of hydroquinone hydroxylase are discussed.
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Affiliation(s)
- M H Eppink
- Department of Biomolecular Sciences, Laboratory of Biochemistry, Wageningen University, The Netherlands
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40
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Suske WA, van Berkel WJ, Kohler HP. Catalytic mechanism of 2-hydroxybiphenyl 3-monooxygenase, a flavoprotein from Pseudomonas azelaica HBP1. J Biol Chem 1999; 274:33355-65. [PMID: 10559214 DOI: 10.1074/jbc.274.47.33355] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
2-Hydroxybiphenyl 3-monooxygenase (EC 1.14.13.44) from Pseudomonas azelaica HBP1 is an FAD-dependent aromatic hydroxylase that catalyzes the conversion of 2-hydroxybiphenyl to 2, 3-dihydroxybiphenyl in the presence of NADH and oxygen. The catalytic mechanism of this three-substrate reaction was investigated at 7 degrees C by stopped-flow absorption spectroscopy. Various individual steps associated with catalysis were readily observed at pH 7.5, the optimum pH for enzyme turnover. Anaerobic reduction of the free enzyme by NADH is a biphasic process, most likely reflecting the presence of two distinct enzyme forms. Binding of 2-hydroxybiphenyl stimulated the rate of enzyme reduction by NADH by 2 orders of magnitude. The anaerobic reduction of the enzyme-substrate complex involved the formation of a transient charge-transfer complex between the reduced flavin and NAD(+). A similar transient intermediate was formed when the enzyme was complexed with the substrate analog 2-sec-butylphenol or with the non-substrate effector 2,3-dihydroxybiphenyl. Excess NAD(+) strongly stabilized the charge-transfer complexes but did not give rise to the appearance of any intermediate during the reduction of uncomplexed enzyme. Free reduced 2-hydroxybiphenyl 3-monooxygenase reacted rapidly with oxygen to form oxidized enzyme with no appearance of intermediates during this reaction. In the presence of 2-hydroxybiphenyl, two consecutive spectral intermediates were observed which were assigned to the flavin C(4a)-hydroperoxide and the flavin C(4a)-hydroxide, respectively. No oxygenated flavin intermediates were observed when the enzyme was in complex with 2, 3-dihydroxybiphenyl. Monovalent anions retarded the dehydration of the flavin C(4a)-hydroxide without stabilization of additional intermediates. The kinetic data for 2-hydroxybiphenyl 3-monooxygenase are consistent with a ternary complex mechanism in which the aromatic substrate has strict control in both the reductive and oxidative half-reaction in a way that reactions leading to substrate hydroxylation are favored over those leading to the futile formation of hydrogen peroxide. NAD(+) release from the reduced enzyme-substrate complex is the slowest step in catalysis.
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Affiliation(s)
- W A Suske
- Department of Microbiology, Swiss Federal Institute of Environmental Sciences and Technology (EAWAG), CH-8600 Dübendorf, The Netherlands
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41
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Eppink MH, Overkamp KM, Schreuder HA, Van Berkel WJ. Switch of coenzyme specificity of p-hydroxybenzoate hydroxylase. J Mol Biol 1999; 292:87-96. [PMID: 10493859 DOI: 10.1006/jmbi.1999.3015] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
p-Hydroxybenzoate hydroxylase (PHBH) is the archetype of the family of NAD(P)H-dependent flavoprotein aromatic hydroxylases. These enzymes share a conserved FAD-binding domain but lack a recognizable fold for binding the pyridine nucleotide. We have switched the coenzyme specificity of strictly NADPH-dependent PHBH from Pseudomonas fluorescens by site-directed mutagenesis. To that end, we altered the solvent exposed helix H2 region (residues 33-40) of the FAD-binding domain. Non-conservative selective replacements of Arg33 and Tyr38 weakened the binding of NADPH without disturbing the protein architecture. Introduction of a basic residue at position 34 increased the NADPH binding strength. Double (M2) and quadruple (M4) substitutions in the N-terminal part of helix H2 did not change the coenzyme specificity. By extending the replacements towards residues 38 and 40, M5 and M6 mutants were generated which were catalytically more efficient with NADH than with NADPH. It is concluded that specificity in P. fluorescens PHBH is conferred by interactions of Arg33, Tyr38 and Arg42 with the 2'-phosphate moiety of bound NADPH, and that introduction of an acidic group at position 38 potentially enables the recognition of the 2'-hydroxy group of NADH. This is the first report on the coenzyme reversion of a flavoprotein aromatic hydroxylase.
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Affiliation(s)
- M H Eppink
- Department of Biomolecular Sciences, Laboratory of Biochemistry, Wageningen University, Wageningen, 6703 HA, The Netherlands
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42
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Eppink MH, Schreuder HA, van Berkel WJ. Interdomain binding of NADPH in p-hydroxybenzoate hydroxylase as suggested by kinetic, crystallographic and modeling studies of histidine 162 and arginine 269 variants. J Biol Chem 1998; 273:21031-9. [PMID: 9694855 DOI: 10.1074/jbc.273.33.21031] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The conserved residues His-162 and Arg-269 of the flavoprotein p-hydroxybenzoate hydroxylase (EC 1.14.13.2) are located at the entrance of the interdomain cleft that leads toward the active site. To study their putative role in NADPH binding, His-162 and Arg-269 were selectively changed by site-specific mutagenesis. The catalytic properties of H162R, H162Y, and R269K were similar to the wild-type enzyme. However, less conservative His-162 and Arg-269 replacements strongly impaired NADPH binding without affecting the conformation of the flavin ring and the efficiency of substrate hydroxylation. The crystal structures of H162R and R269T in complex with 4-hydroxybenzoate were solved at 3.0 and 2.0 A resolution, respectively. Both structures are virtually indistinguishable from the wild-type enzyme-substrate complex except for the substituted side chains. In contrast to wild-type p-hydroxybenzoate hydroxylase, H162R is not inactivated by diethyl pyrocarbonate. NADPH protects wild-type p-hydroxybenzoate hydroxylase from diethylpyrocarbonate inactivation, suggesting that His-162 is involved in NADPH binding. Based on these results and GRID calculations we propose that the side chains of His-162 and Arg-269 interact with the pyrophosphate moiety of NADPH. An interdomain binding mode for NADPH is proposed which takes a novel sequence motif (Eppink, M. H. M., Schreuder, H. A., and van Berkel, W. J. H. (1997) Protein Sci. 6, 2454-2458) into account.
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Affiliation(s)
- M H Eppink
- Department of Biomolecular Sciences, Laboratory of Biochemistry, Wageningen Agricultural University, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands
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43
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van der Bolt FJ, Vervoort J, van Berkel WJ. Flavin motion in p-hydroxybenzoate hydroxylase. Substrate and effector specificity of the Tyr22-->Ala mutant. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 237:592-600. [PMID: 8647102 DOI: 10.1111/j.1432-1033.1996.0592p.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The side chain of Tyr222 in p-hydroxybenzoate hydroxylase interacts with the carboxy moiety of the substrate. Studies on the Tyr222-->Phe mutant, [F222]p-hydroxybenzoate hydroxylase, have shown that disruption of this interaction hampers the hydroxylation of 4-hydroxybenzoate. Tyr222 is possibly involved in flavin motion, which may facilitate the exchange of substrate and product during catalysis. To elucidate the function of Tyr222 in more detail, in the present study the substrate and effector specificity of the Tyr222-->Ala mutant, [A222]p-hydroxybenzoate hydroxylase, was investigated. Replacement of Tyr222 by Ala impairs the binding of the physiological substrate 4-hydroxybenzoate and the substrate analog 4-aminobenzoate. With these compounds, [A222]p-hydroxybenzoate hydroxylase mainly acts as a NADPH oxidase. [A222]p-hydroxybenzoate hydroxylase tightly interacts with 2,4-dihydroxybenzoate and 2-hydroxy-4-aminobenzoate. Crystallographic data [Schreuder, H.A., Mattevi, A., Oblomova, G., Kalk, K.H., Hol, W.G.J., van der Bolt, F.J.T. & van Berkel, W.J.H. (1994) Biochemistry 33, 10161-10170] suggest that this is due to motion of the flavin ring out of the active site, allowing hydrogen-bond interaction between the 2-hydroxy group of the substrate analogs and N3 of the flavin. [A222]p-Hydroxybenzoate hydroxylase produces about 0.6 mol 2,3,4-trihydroxybenzoate from 2,4-dihydroxybenzoate/mol NADPH oxidized. This indicates that reduction of the Tyr222-->Ala mutant shifts the equilibrium of flavin conformers towards the productive "in' position. [A222]p-Hydroxybenzoate hydroxylase converts 2-fluoro-4-hydroxybenzoate to 2-fluoro-3,4-dihydroxybenzoate. The regioselectivity of hydroxylation suggests that [A222]p-hydroxybenzoate hydroxylase binds the fluorinated substrate in the same orientation as wild-type. Spectral studies suggest that wild-type and [A222]p-hydroxybenzoate hydroxylase bind 2-fluoro-4-hydroxybenzoate in the phenolate form with the flavin ring preferring the "out' conformation. Despite activation of the fluorinated substrate and in contrast to the wild-type enzyme, [A222]p-hydroxybenzoate hydroxylase largely produces hydrogen peroxide. The effector specificity of p-hydroxybenzoate hydroxylase is not changed by the Tyr222-->Ala replacement. This supports the idea that the effector specificity is mainly dictated by the protein-substrate interactions at the re-side of the flavin ring.
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Affiliation(s)
- F J van der Bolt
- Department of Biochemistry, Wageningen Agricultural University, The Netherlands
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44
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Murthy YV, Massey V. Chemical modification of the N-10 ribityl side chain of flavins. Effects on properties of flavoprotein disulfide oxidoreductases. J Biol Chem 1995; 270:28586-94. [PMID: 7499374 DOI: 10.1074/jbc.270.48.28586] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Three flavin derivatives modified at the 2'-position of the flavin N-10 ribityl side chain were synthesized: arabinoflavin, 2'-F-2'-deoxyarabinoflavin, and 2'-deoxyriboflavin. These were converted to the FAD level with FAD synthetase. Apoproteins of lipoamide dehydrogenase, glutathione reductase, and mercuric reductase, a family of flavoprotein oxidoreductases, were reconstituted with these flavins. Significant reduction of the catalytic activities was observed with the modified enzymes. During anaerobic reduction of the modified enzymes with substrate or dithiothreitol, decreased thermodynamic stability of the two-electron reduced enzyme forms (EH2) and the accumulation of the four-electron reduced forms (EH4) noted. This effect was more pronounced in case of arabino-FAD-reconstituted enzymes than with the other two. It was found that NAD+ binding influences the interaction between the flavin and the reduced disulfide in the 2'-F-arabino-FAD-lipoamide dehydrogenase, presumably by altering the relative oxidation-reduction potentials. 19F NMR data were obtained for different forms of the 2'-F-arabino-FAD-lipoamide dehydrogenase, which suggest marked conformational changes from one form to the other. The 19F NMR data for the oxidized forms of all three 2'-F-arabino-FAD proteins suggest that the fluorine experiences very similar chemical environments at the active sites.
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Affiliation(s)
- Y V Murthy
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor 48105-0606, USA
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45
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Eppink MH, Schreuder HA, Van Berkel WJ. Structure and function of mutant Arg44Lys of 4-hydroxybenzoate hydroxylase implications for NADPH binding. EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 231:157-65. [PMID: 7628466 DOI: 10.1111/j.1432-1033.1995.0157f.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Arg44, located at the si-face side of the flavin ring in 4-hydroxybenzoate hydroxylase, was changed to lysine by site-specific mutagenesis. Crystals of [R44K]4-hydroxybenzoate hydroxylase complexed with 4-hydroxybenzoate diffract to 0.22-nm resolution. The structure of [R44K]4-hydroxybenzoate hydroxylase is identical to the wild-type enzyme except for local changes in the vicinity of the mutation. The peptide unit between Ile43 and Lys44 is flipped by about 180 degrees in 50% of the molecules. The phi, psi angles in both the native and flipped conformation are outside the allowed regions and indicate a strained conformation. [R44K]4-Hydroxybenzoate hydroxylase has a decreased affinity for the flavin prosthetic group. This is ascribed to the lost interactions between the side chain of Arg44 and the diphosphoribose moiety of the FAD. The replacement of Arg44 by Lys does not change the position of the flavin ring which occupies the same interior position as in wild type. [R44K]4-Hydroxybenzoate hydroxylase fully couples flavin reduction to substrate hydroxylation. Stopped-flow kinetics showed that the effector role of 4-hydroxybenzoate is largely conserved in the mutant. Replacement of Arg44 by Lys however affects NADPH binding, resulting in a low yield of the charge-transfer species between reduced flavin and NADP+. It is inferred from these data that Arg44 is indispensable for optimal catalysis.
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Affiliation(s)
- M H Eppink
- Department of Biochemistry, Agricultural University, Wageningen, The Netherlands
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