A Fungal Ascorbate Oxidase with Unexpected Laccase Activity
Ascorbate oxidases are an enzyme group that has not been explored to a large extent. So far, mainly ascorbate oxidases from plants and only a few from fungi have been described. Although ascorbate oxidases belong to the well-studied enzyme family of multi-copper oxidases, their function is still unc...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Article |
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MDPI AG
2020-08-01
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| Series: | International Journal of Molecular Sciences |
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| Online Access: | https://www.mdpi.com/1422-0067/21/16/5754 |
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| author | Verena Braunschmid Sarah Fuerst Veronika Perz Sabine Zitzenbacher Javier Hoyo Cesar Fernandez-Sanchez Tzanko Tzanov Georg Steinkellner Karl Gruber Gibson S. Nyanhongo Doris Ribitsch Georg M. Guebitz |
| author_facet | Verena Braunschmid Sarah Fuerst Veronika Perz Sabine Zitzenbacher Javier Hoyo Cesar Fernandez-Sanchez Tzanko Tzanov Georg Steinkellner Karl Gruber Gibson S. Nyanhongo Doris Ribitsch Georg M. Guebitz |
| author_sort | Verena Braunschmid |
| collection | DOAJ |
| description | Ascorbate oxidases are an enzyme group that has not been explored to a large extent. So far, mainly ascorbate oxidases from plants and only a few from fungi have been described. Although ascorbate oxidases belong to the well-studied enzyme family of multi-copper oxidases, their function is still unclear. In this study, <i>Af</i>_AO1, an enzyme from the fungus <i>Aspergillus flavus</i>, was characterized. Sequence analyses and copper content determination demonstrated <i>Af</i>_AO1 to belong to the multi-copper oxidase family. Biochemical characterization and 3D-modeling revealed a similarity to ascorbate oxidases, but also to laccases. <i>Af</i>_AO1 had a 10-fold higher affinity to ascorbic acid (<i>K<sub>M</sub></i> = 0.16 ± 0.03 mM) than to ABTS (<i>K<sub>M</sub></i> = 1.89 ± 0.12 mM). Furthermore, the best fitting 3D-model was based on the ascorbate oxidase from <i>Cucurbita pepo</i> var. <i>melopepo</i>. The laccase-like activity of <i>Af</i>_AO1 on ABTS (<i>V<sub>max</sub></i> = 11.56 ± 0.15 µM/min/mg) was, however, not negligible. On the other hand, other typical laccase substrates, such as syringaldezine and guaiacol, were not oxidized by <i>Af</i>_AO1. According to the biochemical and structural characterization, <i>Af</i>_AO1 was classified as ascorbate oxidase with unusual, laccase-like activity. |
| first_indexed | 2024-03-10T17:39:12Z |
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| institution | Directory Open Access Journal |
| issn | 1661-6596 1422-0067 |
| language | English |
| last_indexed | 2024-03-10T17:39:12Z |
| publishDate | 2020-08-01 |
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| series | International Journal of Molecular Sciences |
| spelling | doaj.art-f3cc810b70614b4eabce8b6d9225cbd62023-11-20T09:47:11ZengMDPI AGInternational Journal of Molecular Sciences1661-65961422-00672020-08-012116575410.3390/ijms21165754A Fungal Ascorbate Oxidase with Unexpected Laccase ActivityVerena Braunschmid0Sarah Fuerst1Veronika Perz2Sabine Zitzenbacher3Javier Hoyo4Cesar Fernandez-Sanchez5Tzanko Tzanov6Georg Steinkellner7Karl Gruber8Gibson S. Nyanhongo9Doris Ribitsch10Georg M. Guebitz11Institute of Environmental Biotechnology, Department of Agrobiotechnology, University of Natural Resources and Life Sciences (BOKU), 3430 Tulln an der Donau, AustriaAustrian Centre for Industrial Biotechnology (ACIB), 3430 Tulln an der Donau, AustriaInstitute of Environmental Biotechnology, Department of Agrobiotechnology, University of Natural Resources and Life Sciences (BOKU), 3430 Tulln an der Donau, AustriaInstitute of Environmental Biotechnology, Department of Agrobiotechnology, University of Natural Resources and Life Sciences (BOKU), 3430 Tulln an der Donau, AustriaGrup de Biotecnologia Molecular i Industrial, Department d’Enginyeria Química, Universitat Politècnica de Catalunya, Rambla Sant Nebridi, 08222 Terrassa, SpainInstituto de Microelectronica de Barcelona (IMB-CNM), CSIC, Campus UAB, 08193 Bellatera, SpainGrup de Biotecnologia Molecular i Industrial, Department d’Enginyeria Química, Universitat Politècnica de Catalunya, Rambla Sant Nebridi, 08222 Terrassa, SpainAustrian Centre for Industrial Biotechnology (ACIB), 3430 Tulln an der Donau, AustriaAustrian Centre for Industrial Biotechnology (ACIB), 3430 Tulln an der Donau, AustriaInstitute of Environmental Biotechnology, Department of Agrobiotechnology, University of Natural Resources and Life Sciences (BOKU), 3430 Tulln an der Donau, AustriaInstitute of Environmental Biotechnology, Department of Agrobiotechnology, University of Natural Resources and Life Sciences (BOKU), 3430 Tulln an der Donau, AustriaInstitute of Environmental Biotechnology, Department of Agrobiotechnology, University of Natural Resources and Life Sciences (BOKU), 3430 Tulln an der Donau, AustriaAscorbate oxidases are an enzyme group that has not been explored to a large extent. So far, mainly ascorbate oxidases from plants and only a few from fungi have been described. Although ascorbate oxidases belong to the well-studied enzyme family of multi-copper oxidases, their function is still unclear. In this study, <i>Af</i>_AO1, an enzyme from the fungus <i>Aspergillus flavus</i>, was characterized. Sequence analyses and copper content determination demonstrated <i>Af</i>_AO1 to belong to the multi-copper oxidase family. Biochemical characterization and 3D-modeling revealed a similarity to ascorbate oxidases, but also to laccases. <i>Af</i>_AO1 had a 10-fold higher affinity to ascorbic acid (<i>K<sub>M</sub></i> = 0.16 ± 0.03 mM) than to ABTS (<i>K<sub>M</sub></i> = 1.89 ± 0.12 mM). Furthermore, the best fitting 3D-model was based on the ascorbate oxidase from <i>Cucurbita pepo</i> var. <i>melopepo</i>. The laccase-like activity of <i>Af</i>_AO1 on ABTS (<i>V<sub>max</sub></i> = 11.56 ± 0.15 µM/min/mg) was, however, not negligible. On the other hand, other typical laccase substrates, such as syringaldezine and guaiacol, were not oxidized by <i>Af</i>_AO1. According to the biochemical and structural characterization, <i>Af</i>_AO1 was classified as ascorbate oxidase with unusual, laccase-like activity.https://www.mdpi.com/1422-0067/21/16/5754ascorbate oxidaselaccasemulti-copper oxidaseABTS |
| spellingShingle | Verena Braunschmid Sarah Fuerst Veronika Perz Sabine Zitzenbacher Javier Hoyo Cesar Fernandez-Sanchez Tzanko Tzanov Georg Steinkellner Karl Gruber Gibson S. Nyanhongo Doris Ribitsch Georg M. Guebitz A Fungal Ascorbate Oxidase with Unexpected Laccase Activity International Journal of Molecular Sciences ascorbate oxidase laccase multi-copper oxidase ABTS |
| title | A Fungal Ascorbate Oxidase with Unexpected Laccase Activity |
| title_full | A Fungal Ascorbate Oxidase with Unexpected Laccase Activity |
| title_fullStr | A Fungal Ascorbate Oxidase with Unexpected Laccase Activity |
| title_full_unstemmed | A Fungal Ascorbate Oxidase with Unexpected Laccase Activity |
| title_short | A Fungal Ascorbate Oxidase with Unexpected Laccase Activity |
| title_sort | fungal ascorbate oxidase with unexpected laccase activity |
| topic | ascorbate oxidase laccase multi-copper oxidase ABTS |
| url | https://www.mdpi.com/1422-0067/21/16/5754 |
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