UvA-DARE (Digital Academic Repository) Oxidation reactions catalyzed by Vanadium peroxidases. ten Brink, H.B. Publication date 2000 Link to publication Citation for published version (APA): ten Brink, H. B. (2000). Oxidation reactions catalyzed by Vanadium peroxidases. General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. UvA-DARE is a service provided by the library of the University of Amsterdam (https://dare.uva.nl) Download date:01 Oct 2021 ChapterChapter 3 Sulfoxidationn Activity of Vanadium Bromoperoxidase from AscophyllumAscophyllum nodosum: Evidence for Direct Oxygen Transfer Catalysis J.J. Am. Chem. Soc. submitted for publication Hildaa B. ten Brink,1 Hans E. Schoemaker and Ron Wever 11 E. C. Slater Institute, Biocentrum, University of Amsterdam, Plantage Muidergracht 12, 10188 TV Amsterdam, The Netherlands 22 DSM Research, Bio-organic Chemistry, P.O. Box 18, 6160 MD Geleen, The Netherlands ChapterChapter 3 Sulfoxidationn Activity of Vanadium Bromoperoxidase from As cop hyHum nodosum'.nodosum'. Evidence for Direct Oxygen Transfer Catalysis Hildaa B. ten Brink,1 Hans E. Schoemaker2 and Ron Wever1 11 E.C. Slater Institute, BioCentrum, University of Amsterdam, Plantage Muidergracht 12, 10188 TV Amsterdam, The Netherlands. 22 DSM Research, Bio-Organic Chemistry, P.O. box 18, 6160 MD Geleen, The Netherlands. Abstract t Wee have previously shown that the vanadium bromoperoxidase from AscophyllumAscophyllum nodosum mediates the production of the (R)-enantiomer of methyl phenyll sulfoxide with 91% enantiomeric excess. Investigation of the intrinsic selectivityy of the vanadium bromoperoxidase reveals that the enzyme catalyzes the sulfoxidationn of methyl phenyl sulfide in a purely enantioselective manner. The affinityy of the enzyme for methyl phenyl sulfide was determined to be approximatelyy 3.5 mM in the presence of 25% methanol or tert-butanol. The selectivityy of the sulfoxidation of methyl phenyl sulfide is optimal at a temperature rangee of 25-30°C and can be further optimized by increasing the enzyme concentration,, yielding selectivities with up to 96% enantiomeric excess. Further we establishedd for the first time that the vanadium bromoperoxidase is functional at temperaturess up to 70°C. A detailed investigation of the sulfoxidation activity of thiss enzyme using lsO-labeled hydrogen peroxide shows that the vanadium bromoperoxidasee mediates the direct transfer of the peroxide oxygen to the sulfide. AA schematic model of the vanadium haloperoxidase sulfoxidation mechanism is presented. Introduction n Thee development of catalytic methods for the production of enantiomerically puree sulfoxides has increased in response to scientific and pharmaceutical interest in thesee chiral synthons in asymmetric synthesis.1 Several different methods for the preparationn of chiral sulfoxides by enantioselective oxidation of the corresponding organicc sulfides have been found using both chemical2 and biological, whole-cell3 andd enzymatic, 4' 5' 6 approaches. In particular, the potential application of biocatalystss in the production of these chiral auxiliaries as an alternative to chemical proceduress has been studied in great detail. This is mainly due to the fact that the enzymaticc conversions generally exceed the chemical based reactions in selectivity. 52 2 Inorganicc vanadium (V) peroxo-complexes, some of which have been suggestedd to be functional models for the vanadium peroxidases,7 have been reportedd to mediate oxygen-transfer reactions to a variety of organic compounds includingg sulfides.8 Several chiral Schiff-base ligated vanadium(V) peroxo- complexess have been shown to catalyze the production of optically active sulfoxides,, yielding selectivities up to 78% ee in the conversion of methyl phenyl sulfidee in the presence of hydrogen peroxide to the (5)-enantiomer of the correspondingg sulfoxide.9 Inn line with these results we have recently demonstrated that the vanadium haloperoxidasess are capable of mediating selective sulfoxidation reactions in the presencee of hydrogen peroxide.10 The vanadium bromoperoxidase (VBPO) from the brownn seaweed Ascophyllum nodosum promotes the formation of the (R)- enantiomerr of the methyl phenyl sulfoxide with 91% ee under optimal reaction conditions.. The VBPO from the red seaweed Corallina pilulifera mediates the sulfoxidationn of methyl phenyl sulfide to the (5)-enantiomer of the sulfoxide with 55%% ee. The recombinant VCPO on the other hand produces a racemic mixture of thee sulfoxides, which appeared to be an intrinsic characteristic of the enzyme. In addition,, it has recently been reported that the VBPO from the red seaweed CorallinaCorallina officinalis catalyzes the selective sulfoxidation of small aromatic sulfides andd small sulfides possessing a cis-positioned carboxyl group to the (5)-enantiomer off the corresponding sulfoxides with selectivities exceeding 95% ee.1 however, this enzymee was observed to be incapable of converting methyl phenyl sulfide.113 Thee vanadium haloperoxidases form a group of enzymes that possess a single boundd vanadate ion as a prosthetic group. In the presence of hydrogen peroxide and halidess these enzymes produce hypohalous acid (HOX) as a reactive intermediate, whichh consequently reacts with an organic compound producing a halogenated component.122 The first isolated and characterized vanadium haloperoxidases are the bromoperoxidasess (VBPO's) present in marine algae.13 These organisms are thoughtt to be responsible for the production of large amounts of volatile halogenatedd organic compounds, which are troublesome pollutants contributing to thee destruction of the ozone layer.14 Thee first vanadium-containing bromoperoxidase was found in the brown seaweedd Ascophyllum nodosum and has been studied in great detail.15 Vanadium is presentt as ortho-vanadate in the active site of this peroxidase, one metal atom per enzymee molecule, and the metal was shown to reside in the highest oxidation state, V(V),, even during catalysis.150 Upon reduction to V(IV), which can be observed 53 3 usingg EPR, the enzyme is completely inactive.150 The VBPO from A. nodosum oxidizess bromide in the presence of hydrogen peroxide through a so called "bi bi pingg pong mechanism";15f first hydrogen peroxide binds to the vanadium metal formingg an activated peroxo-intermediate, which facilitates the attack of the halide too yield hypobromous acid, which can further react with either an organic compoundd or an additional equivalent of hydrogen peroxide to form the halogenated componentt or singlet molecular oxygen, respectively. Severall structural studies have been conducted to characterize the nature of the activee site using different techniques, including EPR, EXAFS and XANES,15d'16d'17 andd though the enzyme has been crystallized the 3-D structure this enzyme is not knownn at present.1S Also the complete primary structure of the enzyme has not been reportedd yet.19 Unfortunately no spectroscopic studies can be performed due to the naturee of the vanadate prosthetic group. Ann extraordinary feature of this enzyme from the brown seaweed, which is actuallyy shared by all vanadium peroxidases, is the remarkable stability. ' ' e' Thee VBPO retains complete functionality upon storage in up to 60% of methanol, ethanoll and isopropanol, remains active when exposed to temperatures up to 70 °C andd was observed to be unaffected by detergents and to withstand oxidative inactivationn in the presence of high concentrations of highly reactive oxidants, includingg hydrogen peroxide and hypohalous acid. These fascinating features are of considerablee interest for the potential application of this vanadium peroxidase as (industrial)) biocatalyst in organic synthesis. Moree recently a vanadium chloroperoxidase was discovered and studied in evenn greater detail.21 This enzyme was isolated from the fungus Curvularia inaequalis.inaequalis. In contrast to the bromoperoxidases, chloroperoxidases (VCPO's) mainlyy originate from terrestrial fungi.22 Kinetic studies revealed that the chloride oxidationn mechanism of this enzyme is similar to the bromide oxidation mechanism off the vanadium bromoperoxidase, although the kinetic parameters differ. Thee VCPO has been successfully expressed in the yeast Saccharomyces cerevisiae,cerevisiae, therefore the recombinant VCPO can easily be acquired in large quantities.233 In contrast to the vanadium bromoperoxidase, the primary structure and thee X-ray structure of this enzyme are known.24 Sequence comparisons have shown thatt the architecture of the active site in the VBPO and VCPO is very similar.234'24b Directt evidence for the formation of an active enzyme-peroxo-intermediate in VCPOO during catalysis has been obtained from X-ray crystallography.25 The side-on coordinationn of the peroxide