1
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Eggerichs D, Weindorf N, Mascotti ML, Welzel N, Fraaije MW, Tischler D. Vanillyl alcohol oxidase from Diplodia corticola: Residues Ala420 and Glu466 allow for efficient catalysis of syringyl derivatives. J Biol Chem 2023; 299:104898. [PMID: 37295774 PMCID: PMC10404669 DOI: 10.1016/j.jbc.2023.104898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 05/31/2023] [Accepted: 06/05/2023] [Indexed: 06/12/2023] Open
Abstract
Vanillyl alcohol oxidases (VAOs) belong to the 4-phenol oxidases family and are found predominantly in lignin-degrading ascomycetes. Systematical investigation of the enzyme family at the sequence level resulted in discovery and characterization of the second recombinantly produced VAO member, DcVAO, from Diplodia corticola. Remarkably high activities for 2,6-substituted substrates like 4-allyl-2,6-dimethoxy-phenol (3.5 ± 0.02 U mg-1) or 4-(hydroxymethyl)-2,6-dimethoxyphenol (6.3 ± 0.5 U mg-1) were observed, which could be attributed to a Phe to Ala exchange in the catalytic center. In order to rationalize this rare substrate preference among VAOs, we resurrected and characterized three ancestral enzymes and performed mutagenesis analyses. The results indicate that a Cys/Glu exchange was required to retain activity for ɣ-hydroxylations and shifted the acceptance towards benzyl ethers (up to 4.0 ± 0.1 U mg-1). Our findings contribute to the understanding of the functionality of VAO enzyme group, and with DcVAO, we add a new enzyme to the repertoire of ether cleaving biocatalysts.
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Affiliation(s)
- Daniel Eggerichs
- Department of Microbial Biotechnology, Ruhr-University Bochum, Bochum, Germany
| | - Nils Weindorf
- Department of Microbial Biotechnology, Ruhr-University Bochum, Bochum, Germany
| | - Maria Laura Mascotti
- Department of Molecular Enzymology, University of Groningen, Groningen, The Netherlands; Facultad de Química Bioquímica y Farmacia, IMIBIO-SL CONICET, Universidad Nacional de San Luis, San Luis, Argentina
| | - Natalie Welzel
- Department of Microbial Biotechnology, Ruhr-University Bochum, Bochum, Germany
| | - Marco W Fraaije
- Department of Molecular Enzymology, University of Groningen, Groningen, The Netherlands
| | - Dirk Tischler
- Department of Microbial Biotechnology, Ruhr-University Bochum, Bochum, Germany.
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2
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Guo Y, Alvigini L, Trajkovic M, Alonso-Cotchico L, Monza E, Savino S, Marić I, Mattevi A, Fraaije MW. Structure- and computational-aided engineering of an oxidase to produce isoeugenol from a lignin-derived compound. Nat Commun 2022; 13:7195. [PMID: 36418310 PMCID: PMC9684555 DOI: 10.1038/s41467-022-34912-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 11/11/2022] [Indexed: 11/26/2022] Open
Abstract
Various 4-alkylphenols can be easily obtained through reductive catalytic fractionation of lignocellulosic biomass. Selective dehydrogenation of 4-n-propylguaiacol results in the formation of isoeugenol, a valuable flavor and fragrance molecule and versatile precursor compound. Here we present the engineering of a bacterial eugenol oxidase to catalyze this reaction. Five mutations, identified from computational predictions, are first introduced to render the enzyme more thermostable. Other mutations are then added and analyzed to enhance chemoselectivity and activity. Structural insight demonstrates that the slow catalytic activity of an otherwise promising enzyme variant is due the formation of a slowly-decaying covalent substrate-flavin cofactor adduct that can be remedied by targeted residue changes. The final engineered variant comprises eight mutations, is thermostable, displays good activity and acts as a highly chemoselective 4-n-propylguaiacol oxidase. We lastly use our engineered biocatalyst in an illustrative preparative reaction at gram-scale. Our findings show that a natural enzyme can be redesigned into a tailored biocatalyst capable of valorizing lignin-based monophenols.
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Affiliation(s)
- Yiming Guo
- grid.4830.f0000 0004 0407 1981Molecular Enzymology Group, University of Groningen, Groningen, the Netherlands
| | - Laura Alvigini
- grid.8982.b0000 0004 1762 5736Department of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, Pavia, Italy
| | - Milos Trajkovic
- grid.4830.f0000 0004 0407 1981Molecular Enzymology Group, University of Groningen, Groningen, the Netherlands
| | | | | | - Simone Savino
- grid.4830.f0000 0004 0407 1981Molecular Enzymology Group, University of Groningen, Groningen, the Netherlands
| | - Ivana Marić
- grid.4830.f0000 0004 0407 1981Molecular Enzymology Group, University of Groningen, Groningen, the Netherlands
| | - Andrea Mattevi
- grid.8982.b0000 0004 1762 5736Department of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, Pavia, Italy
| | - Marco W. Fraaije
- grid.4830.f0000 0004 0407 1981Molecular Enzymology Group, University of Groningen, Groningen, the Netherlands
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3
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WANG M, ZHANG W, WANG N. Covalent flavoproteins: types, occurrence, biogenesis and catalytic mechanisms. Chin J Nat Med 2022; 20:749-760. [DOI: 10.1016/s1875-5364(22)60194-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2022] [Indexed: 11/03/2022]
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4
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Alvigini L, Gran-Scheuch A, Guo Y, Trajkovic M, Saifuddin M, Fraaije MW, Mattevi A. Discovery, Biocatalytic Exploration and Structural Analysis of a 4-Ethylphenol Oxidase from Gulosibacter chungangensis. Chembiochem 2021; 22:3225-3233. [PMID: 34523783 PMCID: PMC9293466 DOI: 10.1002/cbic.202100457] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Revised: 09/14/2021] [Indexed: 11/21/2022]
Abstract
The vanillyl‐alcohol oxidase (VAO) family is a rich source of biocatalysts for the oxidative bioconversion of phenolic compounds. Through genome mining and sequence comparisons, we found that several family members lack a generally conserved catalytic aspartate. This finding led us to study a VAO‐homolog featuring a glutamate residue in place of the common aspartate. This 4‐ethylphenol oxidase from Gulosibacter chungangensis (Gc4EO) shares 42 % sequence identity with VAO from Penicillium simplicissimum, contains the same 8α‐N3‐histidyl‐bound FAD and uses oxygen as electron acceptor. However, Gc4EO features a distinct substrate scope and product specificity as it is primarily effective in the dehydrogenation of para‐substituted phenols with little generation of hydroxylated products. The three‐dimensional structure shows that the characteristic glutamate side chain creates a closely packed environment that may limit water accessibility and thereby protect from hydroxylation. With its high thermal stability, well defined structural properties and high expression yields, Gc4EO may become a catalyst of choice for the specific dehydrogenation of phenolic compounds bearing small substituents.
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Affiliation(s)
- Laura Alvigini
- Department of Biology and Biotechnology "Lazzaro Spallanzani", University of Pavia, Via Ferrata 9, 27100, Pavia, Italy
| | - Alejandro Gran-Scheuch
- Molecular Enzymology Group, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Yiming Guo
- Molecular Enzymology Group, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Milos Trajkovic
- Molecular Enzymology Group, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Mohammad Saifuddin
- Molecular Enzymology Group, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Marco W Fraaije
- Molecular Enzymology Group, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Andrea Mattevi
- Department of Biology and Biotechnology "Lazzaro Spallanzani", University of Pavia, Via Ferrata 9, 27100, Pavia, Italy
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5
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Tjallinks G, Martin C, Fraaije MW. Enantioselective oxidation of secondary alcohols by the flavoprotein alcohol oxidase from Phanerochaete chrysosporium. Arch Biochem Biophys 2021; 704:108888. [PMID: 33910055 DOI: 10.1016/j.abb.2021.108888] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 04/14/2021] [Accepted: 04/16/2021] [Indexed: 11/19/2022]
Abstract
The enantioselective oxidation of secondary alcohols represents a valuable approach for the synthesis of optically pure compounds. Flavoprotein oxidases can catalyse such selective transformations by merely using oxygen as electron acceptor. While many flavoprotein oxidases preferably act on primary alcohols, the FAD-containing alcohol oxidase from Phanerochaete chrysosporium was found to be able to perform kinetic resolutions of several secondary alcohols. By selective oxidation of the (S)-alcohols, the (R)-alcohols were obtained in high enantiopurity. In silico docking studies were carried out in order to substantiate the observed (S)-selectivity. Several hydrophobic and aromatic residues in the substrate binding site create a cavity in which the substrates can comfortably undergo van der Waals and pi-stacking interactions. Consequently, oxidation of the secondary alcohols is restricted to one of the two enantiomers. This study has uncovered the ability of an FAD-containing alcohol oxidase, that is known for oxidizing small primary alcohols, to perform enantioselective oxidations of various secondary alcohols.
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Affiliation(s)
- Gwen Tjallinks
- Molecular Enzymology Group, University of Groningen, Nijenborgh 4, Groningen, the Netherlands
| | - Caterina Martin
- Molecular Enzymology Group, University of Groningen, Nijenborgh 4, Groningen, the Netherlands
| | - Marco W Fraaije
- Molecular Enzymology Group, University of Groningen, Nijenborgh 4, Groningen, the Netherlands.
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6
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Abstract
This review presents a historical outline of the research on vanillyl alcohol oxidase (VAO) from Penicillium simplicissimum, one of the canonical members of the VAO/PCMH flavoprotein family. After describing its discovery and initial biochemical characterization, we discuss the physiological role, substrate scope, and catalytic mechanism of VAO, and review its three-dimensional structure and mechanism of covalent flavinylation. We also explain how protein engineering provided a deeper insight into the role of certain amino acid residues in determining the substrate specificity and enantioselectivity of the enzyme. Finally, we summarize recent computational studies about the migration of substrates and products through the enzyme's structure and the phylogenetic distribution of VAO and related enzymes.
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Affiliation(s)
- Tom A Ewing
- Wageningen Food & Biobased Research, Wageningen University & Research, Wageningen, The Netherlands
| | - Gudrun Gygli
- Institute for Biological Interfaces, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Marco W Fraaije
- Molecular Enzymology Group, University of Groningen, Groningen, The Netherlands
| | - Willem J H van Berkel
- Laboratory of Food Chemistry, Wageningen University & Research, Wageningen, The Netherlands.
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7
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Abstract
This chapter represents a journey through flavoprotein oxidases. The purpose is to excite the reader curiosity regarding this class of enzymes by showing their diverse applications. We start with a brief overview on oxidases to then introduce flavoprotein oxidases and elaborate on the flavin cofactors, their redox and spectroscopic characteristics, and their role in the catalytic mechanism. The six major flavoprotein oxidase families will be described, giving examples of their importance in biology and their biotechnological uses. Specific attention will be given to a few selected flavoprotein oxidases that are not extensively discussed in other chapters of this book. Glucose oxidase, cholesterol oxidase, 5-(hydroxymethyl)furfural (HMF) oxidase and methanol oxidase are four examples of oxidases belonging to the GMC-like flavoprotein oxidase family and that have been shown to be valuable biocatalysts. Their structural and mechanistic features and recent enzyme engineering will be discussed in details. Finally we give a look at the current trend in research and conclude with a future outlook.
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Affiliation(s)
- Caterina Martin
- Molecular Enzymology Group, University of Groningen, Groningen, The Netherlands
| | - Claudia Binda
- Department of Biology and Biotechnology, University of Pavia, Pavia, Italy
| | - Marco W Fraaije
- Molecular Enzymology Group, University of Groningen, Groningen, The Netherlands.
| | - Andrea Mattevi
- Department of Biology and Biotechnology, University of Pavia, Pavia, Italy
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8
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Shettigar M, Balotra S, Kasprzak A, Pearce SL, Lacey MJ, Taylor MC, Liu JW, Cahill D, Oakeshott JG, Pandey G. Oxidative Catabolism of (+)-Pinoresinol Is Initiated by an Unusual Flavocytochrome Encoded by Translationally Coupled Genes within a Cluster of (+)-Pinoresinol-Coinduced Genes in Pseudomonas sp. Strain SG-MS2. Appl Environ Microbiol 2020; 86:e00375-20. [PMID: 32198167 DOI: 10.1128/AEM.00375-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 03/12/2020] [Indexed: 12/19/2022] Open
Abstract
Burkholderia sp. strain SG-MS1 and Pseudomonas sp. strain SG-MS2 have previously been found to mineralize (+)-pinoresinol through a common catabolic pathway. Here, we used comparative genomics, proteomics, protein semipurification, and heterologous expression to identify a flavoprotein from the vanillyl alcohol oxidase/p-cresol methyl hydroxylase (VAO/PCMH) enzyme family in SG-MS2 that carries out the initial hydroxylation of (+)-pinoresinol at the benzylic carbon. The cognate gene is translationally coupled with a downstream cytochrome gene, and the cytochrome is required for activity. The flavoprotein has a unique combination of cofactor binding and cytochrome requirements for the VAO/PCMH family. The heterologously expressed enzyme has a Km of 1.17 μM for (+)-pinoresinol. The enzyme is overexpressed in strain SG-MS2 upon exposure to (+)-pinoresinol, along with 45 other proteins, 22 of which were found to be encoded by genes in an approximately 35.1-kb cluster also containing the flavoprotein and cytochrome genes. Homologs of 18 of these 22 genes, plus the flavoprotein and cytochrome genes, were also found in a 38.7-kb cluster in SG-MS1. The amino acid identities of four of the other proteins within the SG-MS2 cluster suggest they catalyze conversion of hydroxylated pinoresinol to protocatechuate and 2-methoxyhydroquinone. Nine other proteins upregulated in SG-MS2 on exposure to (+)-pinoresinol appear to be homologs of proteins known to comprise the protocatechuate and 2-methoxyhydroquinone catabolic pathways, but only three of the cognate genes lie within the cluster containing the flavoprotein and cytochrome genes.IMPORTANCE (+)-Pinoresinol is an important plant defense compound, a major food lignan for humans and some other animals, and the model compound used to study degradation of the β-β' linkages in lignin. We report a gene cluster, in one strain each of Pseudomonas and Burkholderia, that is involved in the oxidative catabolism of (+)-pinoresinol. The flavoprotein component of the α-hydroxylase which heads the pathway belongs to the 4-phenol oxidizing (4PO) subgroup of the vanillyl alcohol oxidase/p-cresol methyl hydroxylase (VAO/PCMH) enzyme family but constitutes a novel combination of cofactor and electron acceptor properties for the family. It is translationally coupled with a cytochrome gene whose product is also required for activity. The work casts new light on the biology of (+)-pinoresinol and its transformation to other bioactive molecules. Potential applications of the findings include new options for deconstructing lignin into useful chemicals and the generation of new phytoestrogenic enterolactones from lignans.
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9
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Román R, Lončar N, Casablancas A, Fraaije MW, Gonzalez G. High-level production of industrially relevant oxidases by a two-stage fed-batch approach: overcoming catabolite repression in arabinose-inducible Escherichia coli systems. Appl Microbiol Biotechnol 2020; 104:5337-5345. [PMID: 32322946 DOI: 10.1007/s00253-020-10622-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 04/03/2020] [Accepted: 04/13/2020] [Indexed: 12/21/2022]
Abstract
With the growing interest in enzyme applications, there is an urgent demand for economic, affordable, and flexible enzyme production processes. In the present paper, we developed a high cell density fed-batch process for the production of two cofactor-containing oxidase, 5-hydroxymethylfurfural oxidase (HMFO) and eugenol oxidase (EUGO). The approach involved the arabinose-inducible system to drive the expression while using mineral media. In order to overcome a major drawback of arabinose-inducible promoters, carbon catabolite repression, (CCR) by glucose, we developed a high cell density culture (HCDC), two-stage fed-batch protocol allowing us to reach cell densities exceeding 70 g/L of dry cell weight (DCW) using glucose as carbon source. Then, induction was achieved by adding arabinose, while changing the carbon source to glycerol. This strategy allowed us to obtain an eightfold increase in recombinant HMFO titer when compared with a reference batch fermentation in Erlenmeyer flasks using terrific broth (TB), typically used with arabinose-inducible strains. The optimized protocol was also tested for expression of a structurally unrelated oxidase, EUGO, where a similar yield was achieved. Clearly, this two-step protocol in which a relatively cheap medium (when compared to TB) can be used reduces costs and provides a way to obtain protein production levels similar to those of IPTG-based systems. KEY POINTS: • Arabinose promoters are not well suited for HCDC production due to CCR effect. • This drawback has been overcome by using a two-stage Fed-batch protocol. • Protein yield has been increased by an eightfold factor, improving process economics.
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Affiliation(s)
- Ramón Román
- Fermentation Pilot Plant, Department of Chemical, Biological and Enviromental Engineering, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain.
| | | | - Antoni Casablancas
- Fermentation Pilot Plant, Department of Chemical, Biological and Enviromental Engineering, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain
| | - Marco W Fraaije
- Molecular Enzymology group, University of Groningen, Groningen, The Netherlands
| | - Glòria Gonzalez
- Fermentation Pilot Plant, Department of Chemical, Biological and Enviromental Engineering, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Spain
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10
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Gandomkar S, Jost E, Loidolt D, Swoboda A, Pickl M, Elaily W, Daniel B, Fraaije MW, Macheroux P, Kroutil W. Biocatalytic Enantioselective Oxidation of Sec-Allylic Alcohols with Flavin-Dependent Oxidases. Adv Synth Catal 2019; 361:5264-5271. [PMID: 31894182 PMCID: PMC6919931 DOI: 10.1002/adsc.201900921] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 09/26/2019] [Indexed: 01/17/2023]
Abstract
The oxidation of allylic alcohols is challenging to perform in a chemo- as well as stereo-selective fashion at the expense of molecular oxygen using conventional chemical protocols. Here, we report the identification of a library of flavin-dependent oxidases including variants of the berberine bridge enzyme (BBE) analogue from Arabidopsis thaliana (AtBBE15) and the 5-(hydroxymethyl)furfural oxidase (HMFO) and its variants (V465T, V465S, V465T/W466H and V367R/W466F) for the enantioselective oxidation of sec-allylic alcohols. While primary and benzylic alcohols as well as certain sugars are well known to be transformed by flavin-dependent oxidases, sec-allylic alcohols have not been studied yet except in a single report. The model substrates investigated were oxidized enantioselectively in a kinetic resolution with an E-value of up to >200. For instance HMFO V465S/T oxidized the (S)-enantiomer of (E)-oct-3-en-2-ol (1 a) and (E)-4-phenylbut-3-en-2-ol with E>200 giving the remaining (R)-alcohol with ee>99% at 50% conversion. The enantioselectivity could be decreased if required by medium engineering by the addition of cosolvents (e. g. dimethyl sulfoxide).
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Affiliation(s)
- Somayyeh Gandomkar
- Institute of Chemistry, NAWI Graz, BioTechMed GrazUniversity of GrazHeinrichstr. 288010GrazAustria
| | - Etta Jost
- Institute of Chemistry, NAWI Graz, BioTechMed GrazUniversity of GrazHeinrichstr. 288010GrazAustria
| | - Doris Loidolt
- Institute of Chemistry, NAWI Graz, BioTechMed GrazUniversity of GrazHeinrichstr. 288010GrazAustria
| | - Alexander Swoboda
- Institute of Chemistry, NAWI Graz, BioTechMed GrazUniversity of GrazHeinrichstr. 288010GrazAustria
| | - Mathias Pickl
- Institute of Chemistry, NAWI Graz, BioTechMed GrazUniversity of GrazHeinrichstr. 288010GrazAustria
| | - Wael Elaily
- Institute of BiochemistryGraz University of TechnologyPetersgasse 12/II8010GrazAustria
- Chemistry of Natural & Microbial Products DepartmentNational Research Centre33 El Buhouth St12622CairoEgypt
| | - Bastian Daniel
- Institute of BiochemistryGraz University of TechnologyPetersgasse 12/II8010GrazAustria
- Austrian Centre of Industrial Biotechnology, c/o Institute of Molecular BiosciencesUniversity of GrazHumboldtstraße 508010GrazAustria
| | - Marco W. Fraaije
- Molecular Enzymology GroupUniversity of GroningenNijenborgh 49747AGGroningenThe Netherlands
| | - Peter Macheroux
- Institute of BiochemistryGraz University of TechnologyPetersgasse 12/II8010GrazAustria
| | - Wolfgang Kroutil
- Institute of Chemistry, NAWI Graz, BioTechMed GrazUniversity of GrazHeinrichstr. 288010GrazAustria
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Lubbers RJM, Dilokpimol A, Visser J, Mäkelä MR, Hildén KS, de Vries RP. A comparison between the homocyclic aromatic metabolic pathways from plant-derived compounds by bacteria and fungi. Biotechnol Adv 2019; 37:107396. [PMID: 31075306 DOI: 10.1016/j.biotechadv.2019.05.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 04/18/2019] [Accepted: 05/03/2019] [Indexed: 12/13/2022]
Abstract
Aromatic compounds derived from lignin are of great interest for renewable biotechnical applications. They can serve in many industries e.g. as biochemical building blocks for bioplastics or biofuels, or as antioxidants, flavor agents or food preservatives. In nature, lignin is degraded by microorganisms, which results in the release of homocyclic aromatic compounds. Homocyclic aromatic compounds can also be linked to polysaccharides, tannins and even found freely in plant biomass. As these compounds are often toxic to microbes already at low concentrations, they need to be degraded or converted to less toxic forms. Prior to ring cleavage, the plant- and lignin-derived aromatic compounds are converted to seven central ring-fission intermediates, i.e. catechol, protocatechuic acid, hydroxyquinol, hydroquinone, gentisic acid, gallic acid and pyrogallol through complex aromatic metabolic pathways and used as energy source in the tricarboxylic acid cycle. Over the decades, bacterial aromatic metabolism has been described in great detail. However, the studies on fungal aromatic pathways are scattered over different pathways and species, complicating a comprehensive view of fungal aromatic metabolism. In this review, we depicted the similarities and differences of the reported aromatic metabolic pathways in fungi and bacteria. Although both microorganisms share the main conversion routes, many alternative pathways are observed in fungi. Understanding the microbial aromatic metabolic pathways could lead to metabolic engineering for strain improvement and promote valorization of lignin and related aromatic compounds.
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Affiliation(s)
- Ronnie J M Lubbers
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands.
| | - Adiphol Dilokpimol
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands.
| | - Jaap Visser
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands.
| | - Miia R Mäkelä
- Department of Microbiology, University of Helsinki, Viikinkaari 9, Helsinki, Finland.
| | - Kristiina S Hildén
- Department of Microbiology, University of Helsinki, Viikinkaari 9, Helsinki, Finland.
| | - Ronald P de Vries
- Fungal Physiology, Westerdijk Fungal Biodiversity Institute & Fungal Molecular Physiology, Utrecht University, Uppsalalaan 8, 3584 CT Utrecht, the Netherlands; Department of Microbiology, University of Helsinki, Viikinkaari 9, Helsinki, Finland.
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12
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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] [What about the content of this article? (0)] [Affiliation(s)] [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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Castilla IA, Woods DF, Reen FJ, O'Gara F. Harnessing Marine Biocatalytic Reservoirs for Green Chemistry Applications through Metagenomic Technologies. Mar Drugs 2018; 16:E227. [PMID: 29973493 PMCID: PMC6071119 DOI: 10.3390/md16070227] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Revised: 06/13/2018] [Accepted: 06/22/2018] [Indexed: 01/24/2023] Open
Abstract
In a demanding commercial world, large-scale chemical processes have been widely utilised to satisfy consumer related needs. Chemical industries are key to promoting economic growth and meeting the requirements of a sustainable industrialised society. The market need for diverse commodities produced by the chemical industry is rapidly expanding globally. Accompanying this demand is an increased threat to the environment and to human health, due to waste produced by increased industrial production. This increased demand has underscored the necessity to increase reaction efficiencies, in order to reduce costs and increase profits. The discovery of novel biocatalysts is a key method aimed at combating these difficulties. Metagenomic technology, as a tool for uncovering novel biocatalysts, has great potential and applicability and has already delivered many successful achievements. In this review we discuss, recent developments and achievements in the field of biocatalysis. We highlight how green chemistry principles through the application of biocatalysis, can be successfully promoted and implemented in various industrial sectors. In addition, we demonstrate how two novel lipases/esterases were mined from the marine environment by metagenomic analysis. Collectively these improvements can result in increased efficiency, decreased energy consumption, reduced waste and cost savings for the chemical industry.
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Affiliation(s)
- Ignacio Abreu Castilla
- BIOMERIT Research Centre, School of Microbiology, University College Cork, T12 K8AF Cork, Ireland.
| | - David F Woods
- BIOMERIT Research Centre, School of Microbiology, University College Cork, T12 K8AF Cork, Ireland.
| | - F Jerry Reen
- School of Microbiology, University College Cork, T12 K8AF Cork, Ireland.
| | - Fergal O'Gara
- BIOMERIT Research Centre, School of Microbiology, University College Cork, T12 K8AF Cork, Ireland.
- Telethon Kids Institute, Perth, WA 6008, Australia.
- Human Microbiome Programme, School of Pharmacy and Biomedical Sciences, Curtin Health Innovation Research Institute, Curtin University, Perth, WA 6102, Australia.
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Gygli G, de Vries RP, van Berkel WJ. On the origin of vanillyl alcohol oxidases. Fungal Genet Biol 2018; 116:24-32. [DOI: 10.1016/j.fgb.2018.04.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 03/24/2018] [Accepted: 04/03/2018] [Indexed: 11/16/2022]
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Habib M, Trajkovic M, Fraaije MW. The Biocatalytic Synthesis of Syringaresinol from 2,6-Dimethoxy-4-allylphenol in One-Pot Using a Tailored Oxidase/Peroxidase System. ACS Catal 2018; 8:5549-5552. [PMID: 29888098 PMCID: PMC5989697 DOI: 10.1021/acscatal.8b01235] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 05/11/2018] [Indexed: 11/28/2022]
Abstract
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Syringaresinol
was synthesized in a one-pot conversion containing
eugenol oxidase (EUGO) and horseradish peroxidase (HRP) using the
relatively cheap 2,6-dimethoxy-4-allylphenol as a substrate. This
conversion is fully coupled as the hydrogen peroxide generated from
the reaction of EUGO with the substrate is utilized by the HRP to
convert the formed sinapyl alcohol into syringaresinol. To improve
the performance of EUGO on 2,6-dimethoxy-4-allylphenol,
structure-inspired enzyme engineering was performed. This yielded
the I427A EUGO mutant that is significantly more efficient with 2,6-dimethoxy-4-allylphenol.
The I427A EUGO mutant together with HRP were capable of efficiently
producing syringaresinol as a major product. After optimization and
upscaling the conversion to a semipreparative scale (1 gr), syringaresinol
was obtained in 81% yield.
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Affiliation(s)
- Mohamed Habib
- Molecular Enzymology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen 9747 AG, The Netherlands
- Department of Microbiology and Immunology, Faculty of Pharmacy, Cairo University, Cairo 11562, Egypt
| | - Milos Trajkovic
- Molecular Enzymology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen 9747 AG, The Netherlands
| | - Marco W. Fraaije
- Molecular Enzymology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen 9747 AG, The Netherlands
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Ewing TA, van Noord A, Paul CE, van Berkel WJH. A Xylenol Orange-Based Screening Assay for the Substrate Specificity of Flavin-Dependent para-Phenol Oxidases. Molecules 2018; 23:E164. [PMID: 29342886 DOI: 10.3390/molecules23010164] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Revised: 01/10/2018] [Accepted: 01/11/2018] [Indexed: 11/16/2022] Open
Abstract
Vanillyl alcohol oxidase (VAO) and eugenol oxidase (EUGO) are flavin-dependent enzymes that catalyse the oxidation of para-substituted phenols. This makes them potentially interesting biocatalysts for the conversion of lignin-derived aromatic monomers to value-added compounds. To facilitate their biocatalytic exploitation, it is important to develop methods by which variants of the enzymes can be rapidly screened for increased activity towards substrates of interest. Here, we present the development of a screening assay for the substrate specificity of para-phenol oxidases based on the detection of hydrogen peroxide using the ferric-xylenol orange complex method. The assay was used to screen the activity of VAO and EUGO towards a set of twenty-four potential substrates. This led to the identification of 4-cyclopentylphenol as a new substrate of VAO and EUGO and 4-cyclohexylphenol as a new substrate of VAO. Screening of a small library of VAO and EUGO active-site variants for alterations in their substrate specificity led to the identification of a VAO variant (T457Q) with increased activity towards vanillyl alcohol (4-hydroxy-3-methoxybenzyl alcohol) and a EUGO variant (V436I) with increased activity towards chavicol (4-allylphenol) and 4-cyclopentylphenol. This assay provides a quick and efficient method to screen the substrate specificity of para-phenol oxidases, facilitating the enzyme engineering of known para-phenol oxidases and the evaluation of the substrate specificity of novel para-phenol oxidases.
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Gygli G, Lucas MF, Guallar V, van Berkel WJH. The ins and outs of vanillyl alcohol oxidase: Identification of ligand migration paths. PLoS Comput Biol 2017; 13:e1005787. [PMID: 28985219 PMCID: PMC5646868 DOI: 10.1371/journal.pcbi.1005787] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 10/18/2017] [Accepted: 09/21/2017] [Indexed: 01/03/2023] Open
Abstract
Vanillyl alcohol oxidase (VAO) is a homo-octameric flavoenzyme belonging to the VAO/PCMH family. Each VAO subunit consists of two domains, the FAD-binding and the cap domain. VAO catalyses, among other reactions, the two-step conversion of p-creosol (2-methoxy-4-methylphenol) to vanillin (4-hydroxy-3-methoxybenzaldehyde). To elucidate how different ligands enter and exit the secluded active site, Monte Carlo based simulations have been performed. One entry/exit path via the subunit interface and two additional exit paths have been identified for phenolic ligands, all leading to the si side of FAD. We argue that the entry/exit path is the most probable route for these ligands. A fourth path leading to the re side of FAD has been found for the co-ligands dioxygen and hydrogen peroxide. Based on binding energies and on the behaviour of ligands in these four paths, we propose a sequence of events for ligand and co-ligand migration during catalysis. We have also identified two residues, His466 and Tyr503, which could act as concierges of the active site for phenolic ligands, as well as two other residues, Tyr51 and Tyr408, which could act as a gateway to the re side of FAD for dioxygen. Most of the residues in the four paths are also present in VAO’s closest relatives, eugenol oxidase and p-cresol methylhydroxylase. Key path residues show movements in our simulations that correspond well to conformations observed in crystal structures of these enzymes. Preservation of other path residues can be linked to the electron acceptor specificity and oligomerisation state of the three enzymes. This study is the first comprehensive overview of ligand and co-ligand migration in a member of the VAO/PCMH family, and provides a proof of concept for the use of an unbiased method to sample this process. Enzymes are bionanomachines, which speed up chemical reactions in organisms. To understand how they achieve that, we need to study their mechanisms. Computational enzymology can show us what happens in the enzyme’s active site during a reaction. But molecules need first to reach the active site before a reaction can start. The process of substrate entry and product exit to the active site is often neglected when studying enzymes. However, these two events are of fundamental importance to the proper functioning of any enzyme. We are interested in these dynamic processes to complete our understanding of the mode of action of enzymes. In our work, we have studied substrate and product migration in vanillyl alcohol oxidase. This enzyme can produce the flavour vanillin and enantiopure alcohols, but also catalyses other reactions. The named products are of interest to the flavour- and fine-chemical industries.
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Affiliation(s)
- Gudrun Gygli
- Laboratory of Biochemistry, Wageningen University & Research, Stippeneng 4, WE Wageningen, The Netherlands
| | - Maria Fátima Lucas
- Joint BSC-IRB Research Program in Computational Biology, Barcelona Supercomputing Center, Jordi Girona 29, Barcelona, Spain
| | - Victor Guallar
- Joint BSC-IRB Research Program in Computational Biology, Barcelona Supercomputing Center, Jordi Girona 29, Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys 23, Barcelona, Spain
| | - Willem J. H. van Berkel
- Laboratory of Biochemistry, Wageningen University & Research, Stippeneng 4, WE Wageningen, The Netherlands
- * E-mail:
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Ewing TA, Fraaije MW, Mattevi A, van Berkel WJ. The VAO/PCMH flavoprotein family. Arch Biochem Biophys 2017; 632:104-117. [DOI: 10.1016/j.abb.2017.06.022] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Revised: 06/26/2017] [Accepted: 06/29/2017] [Indexed: 01/15/2023]
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Habib MHM, Deuss PJ, Lončar N, Trajkovic M, Fraaije MW. A Biocatalytic One-Pot Approach for the Preparation of Lignin Oligomers Using an Oxidase/Peroxidase Cascade Enzyme System. Adv Synth Catal 2017. [DOI: 10.1002/adsc.201700650] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Mohamed H. M. Habib
- Molecular Enzymology, Groningen Biomolecular Sciences and Biotechnology Institute; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
- Department of Microbiology and Immunology, Faculty of Pharmacy; Cairo University; Kasr El-Aini Cairo 11562 Egypt
| | - Peter J. Deuss
- Department of Chemical Engineering (ENTEG); University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Nikola Lončar
- GECCO (Groningen Enzyme and Cofactor Collection); University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Milos Trajkovic
- Molecular Enzymology, Groningen Biomolecular Sciences and Biotechnology Institute; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
| | - Marco W. Fraaije
- Molecular Enzymology, Groningen Biomolecular Sciences and Biotechnology Institute; University of Groningen; Nijenborgh 4 9747 AG Groningen The Netherlands
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Ewing TA, Nguyen QT, Allan RC, Gygli G, Romero E, Binda C, Fraaije MW, Mattevi A, van Berkel WJH. Two tyrosine residues, Tyr-108 and Tyr-503, are responsible for the deprotonation of phenolic substrates in vanillyl-alcohol oxidase. J Biol Chem 2017; 292:14668-14679. [PMID: 28717004 DOI: 10.1074/jbc.m117.778449] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 07/05/2017] [Indexed: 11/06/2022] Open
Abstract
A number of oxidoreductases from the VAO/para-cresol methylhydroxylase flavoprotein family catalyze the oxidation of para-substituted phenols. One of the best-studied is vanillyl-alcohol oxidase (VAO) from the fungus Penicillium simplicissimum For oxidation of phenols by VAO to occur, they must first be bound in the active site of the enzyme in their phenolate anion form. The crystal structure of VAO reveals that two tyrosine residues, Tyr-108 and Tyr-503, are positioned to facilitate this deprotonation. To investigate their role in catalysis, we created three VAO variants, Y108F, Y503F, and Y108F/Y503F, and studied their biochemical properties. Steady-state kinetics indicated that the presence of at least one of the tyrosine residues is essential for efficient catalysis by VAO. Stopped-flow kinetics revealed that the reduction of VAO by chavicol or vanillyl alcohol occurs at two different rates: kobs1, which corresponds to its reaction with the deprotonated form of the substrate, and kobs2, which corresponds to its reaction with the protonated form of the substrate. In Y108F, Y503F, and Y108F/Y503F, the relative contribution of kobs2 to the reduction is larger than in wild-type VAO, suggesting deprotonation is impaired in these variants. Binding studies disclosed that the competitive inhibitor isoeugenol is predominantly in its deprotonated form when bound to wild-type VAO, but predominantly in its protonated form when bound to the variants. These results indicate that Tyr-108 and Tyr-503 are responsible for the activation of substrates in VAO, providing new insights into the catalytic mechanism of VAO and related enzymes that oxidize para-substituted phenols.
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Affiliation(s)
- Tom A Ewing
- From the Laboratory of Biochemistry, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands
| | - Quoc-Thai Nguyen
- the Department of Biology and Biotechnology, University of Pavia, Via Ferrata 9, 27100 Pavia, Italy.,the Molecular Enzymology Group, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands, and.,the Faculty of Pharmacy, University of Medicine and Pharmacy, 41 Dinh Tien Hoang Street, Ben Nghe Ward, District 1, Ho Chi Minh City, Vietnam
| | - Robert C Allan
- From the Laboratory of Biochemistry, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands
| | - Gudrun Gygli
- From the Laboratory of Biochemistry, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands
| | - Elvira Romero
- the Molecular Enzymology Group, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands, and
| | - Claudia Binda
- the Department of Biology and Biotechnology, University of Pavia, Via Ferrata 9, 27100 Pavia, Italy
| | - Marco W Fraaije
- the Molecular Enzymology Group, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands, and
| | - Andrea Mattevi
- the Department of Biology and Biotechnology, University of Pavia, Via Ferrata 9, 27100 Pavia, Italy
| | - Willem J H van Berkel
- From the Laboratory of Biochemistry, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands,
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Ewing TA, Gygli G, van Berkel WJH. A single loop is essential for the octamerization of vanillyl alcohol oxidase. FEBS J 2016; 283:2546-59. [PMID: 27214042 DOI: 10.1111/febs.13762] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 05/20/2016] [Indexed: 11/30/2022]
Abstract
UNLABELLED The VAO/PCMH family of flavoenzymes is a family of structurally related proteins that catalyse a wide range of oxidation reactions. It contains a subfamily of enzymes that catalyse the oxidation of para-substituted phenols using covalently bound FAD cofactors (the 4PO subfamily). This subfamily is composed of two oxidases, vanillyl alcohol oxidase (VAO) and eugenol oxidase (EUGO), and two flavocytochrome dehydrogenases, para-cresol methylhydroxylase (PCMH) and eugenol hydroxylase (EUGH). Although they catalyse similar reactions, these enzymes differ in terms of their electron acceptor preference and oligomerization state. For example, VAO forms homo-octamers that can be described as tetramers of stable dimers, whereas EUGO is exclusively dimeric in solution. A possible explanation for this difference is the presence of a loop at the dimer-dimer interface in VAO that is not present in EUGO. Here, the role played by this loop in determining the quaternary structure of these enzymes is investigated. A VAO variant where the loop was deleted, loopless VAO, exclusively formed dimers. However, introduction of the loop into EUGO was not sufficient to induce its octamerization. Neither variant displayed major changes in its catalytic properties as compared to the wild-type enzyme. Bioinformatic analysis revealed that the presence of the loop is conserved within putative fungal oxidases of the 4PO subgroup, but it is never found in putative bacterial oxidases or dehydrogenases. Our results shed light on the molecular mechanism of homo-oligomerization of VAO and the importance of oligomerization for its enzymatic function. ENZYMES p-cresol methylhydroxylase (4-methylphenol:acceptor oxidoreductase (methyl-hydroxylating), EC 1.17.99.1); vanillyl alcohol oxidase (vanillyl alcohol:oxygen oxidoreductase, EC 1.1.3.38).
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Affiliation(s)
- Tom A Ewing
- Laboratory of Biochemistry, Wageningen University, The Netherlands
| | - Gudrun Gygli
- Laboratory of Biochemistry, Wageningen University, The Netherlands
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