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A Fungal Ascorbate Oxidase with Unexpected Laccase Activity

AuthorsBraunschmid, Verena; Fuerst, Sarah; Perz, Veronika; Zitzenbacher, Sabine; Hoyo, Javier; Fernández Sánchez, César ; Tzanov, Tzanko; Steinkellner, Georg; Gruber, Karl; Nyanhongo, Gibson S.; Ribitsch, Doris; Guebitz, Georg M.
KeywordsAscorbate oxidase
Multi-copper oxidase
Issue Date2020
PublisherMultidisciplinary Digital Publishing Institute
CitationInternational Journal of Molecular Sciences 21(16): 5754 (2020)
AbstractAscorbate 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, Af_AO1, an enzyme from the fungus Aspergillus flavus, was characterized. Sequence analyses and copper content determination demonstrated Af_AO1 to belong to the multi-copper oxidase family. Biochemical characterization and 3D-modeling revealed a similarity to ascorbate oxidases, but also to laccases. Af_AO1 had a 10-fold higher affinity to ascorbic acid (KM = 0.16 ± 0.03 mM) than to ABTS (KM = 1.89 ± 0.12 mM). Furthermore, the best fitting 3D-model was based on the ascorbate oxidase from Cucurbita pepo var. melopepo. The laccase-like activity of Af_AO1 on ABTS (Vmax = 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 Af_AO1. According to the biochemical and structural characterization, Af_AO1 was classified as ascorbate oxidase with unusual, laccase-like activity.
Description© 2020 by the authors
Publisher version (URL)https://doi.org/10.3390/ijms21165754
Appears in Collections:(IMB-CNM) Artículos
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