Biomaterial Database

A Fungal Ascorbate Oxidase with Unexpected Laccase Activity. 2020

Verena Braunschmid, and Sarah Fuerst, and Veronika Perz, and Sabine Zitzenbacher, and Javier Hoyo, and Cesar Fernandez-Sanchez, and Tzanko Tzanov, and Georg Steinkellner, and Karl Gruber, and Gibson S Nyanhongo, and Doris Ribitsch, and Georg M Guebitz

Institute of Environmental Biotechnology, Department of Agrobiotechnology, University of Natural Resources and Life Sciences (BOKU), 3430 Tulln an der Donau, Austria.

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, 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 (K = 0.16 ± 0.03 mM) than to ABTS (K = 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 (V = 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.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008958	Models, Molecular	Models used experimentally or theoretically to study molecular shape, electronic properties, or interactions; includes analogous molecules, computer-generated graphics, and mechanical structures.	Molecular Models,Model, Molecular,Molecular Model
D010084	Oxidation-Reduction	A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).	Redox,Oxidation Reduction
D003300	Copper	A heavy metal trace element with the atomic symbol Cu, atomic number 29, and atomic weight 63.55.	Copper-63,Copper 63
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D001204	Ascorbate Oxidase	An enzyme that converts ascorbic acid to dehydroascorbic acid. EC 1.10.3.3.	Ascorbase,Ascorbino Dehydrogenase,L-Ascorbate Oxidase,Dehydrogenase, Ascorbino,L Ascorbate Oxidase,Oxidase, Ascorbate,Oxidase, L-Ascorbate
D001231	Aspergillus flavus	A species of imperfect fungi which grows on peanuts and other plants and produces the carcinogenic substance aflatoxin. It is also used in the production of the antibiotic flavicin.	Aspergillus parvisclerotigenus,Petromyces flavus
D013379	Substrate Specificity	A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.	Specificities, Substrate,Specificity, Substrate,Substrate Specificities
D042845	Laccase	A copper-containing oxidoreductase enzyme that catalyzes the oxidation of 4-benzenediol to 4-benzosemiquinone. It also has activity towards a variety of O-quinols and P-quinols. It primarily found in FUNGI and is involved in LIGNIN degradation, pigment biosynthesis and detoxification of lignin-derived products.	Laccase B,Laccase I,Laccase II,Laccase III,Urishiol Oxidase,p-Diphenol Oxidase,Oxidase, Urishiol,Oxidase, p-Diphenol,p Diphenol Oxidase