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Comparing Ligninolytic Capabilities of Bacterial and Fungal Dye-Decolorizing Peroxidases and Class-II Peroxidase-Catalases
oleh: Dolores Linde, Iván Ayuso-Fernández, Marcos Laloux, José E. Aguiar-Cervera, Antonio L. de Lacey, Francisco J. Ruiz-Dueñas, Angel T. Martínez
Format: | Article |
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Diterbitkan: | MDPI AG 2021-03-01 |
Deskripsi
We aim to clarify the ligninolytic capabilities of dye-decolorizing peroxidases (DyPs) from bacteria and fungi, compared to fungal lignin peroxidase (LiP) and versatile peroxidase (VP). With this purpose, DyPs from <i>Amycolatopsis</i> sp., <i>Thermomonospora curvata</i>, and <i>Auricularia auricula-judae</i>, VP from <i>Pleurotus eryngii</i>, and LiP from <i>Phanerochaete chrysosporium</i> were produced, and their kinetic constants and reduction potentials determined. Sharp differences were found in the oxidation of nonphenolic simple (veratryl alcohol, VA) and dimeric (veratrylglycerol-β- guaiacyl ether, VGE) lignin model compounds, with LiP showing the highest catalytic efficiencies (around 15 and 200 s<sup>−1</sup>·mM<sup>−1</sup> for VGE and VA, respectively), while the efficiency of the <i>A. auricula-judae</i> DyP was 1–3 orders of magnitude lower, and no activity was detected with the bacterial DyPs. VP and LiP also showed the highest reduction potential (1.28–1.33 V) in the rate-limiting step of the catalytic cycle (i.e., compound-II reduction to resting enzyme), estimated by stopped-flow measurements at the equilibrium, while the <i>T. curvata</i> DyP showed the lowest value (1.23 V). We conclude that, when using realistic enzyme doses, only fungal LiP and VP, and in much lower extent fungal DyP, oxidize nonphenolic aromatics and, therefore, have the capability to act on the main moiety of the native lignin macromolecule.