Xie Ning, Ruprich-Robert Gwenaël, Silar Philippe, Chapeland-Leclerc Florence
Sorbonne Paris Cité, Institut des Energies de Demain (IED), Université Paris Diderot, UMR 8236, 75205, Paris, France; Institut de Génétique et Microbiologie, Université Paris Sud, UMR 8621, 91405, Orsay, France.
Environ Microbiol. 2015 Mar;17(3):866-75. doi: 10.1111/1462-2920.12549. Epub 2014 Jul 21.
Plant biomass degradation by fungi is a critical step for production of biofuels, and laccases are common ligninolytic enzymes envisioned for ligninolysis. Bilirubin oxidases (BODs)-like are related to laccases, but their roles during lignocellulose degradation have not yet been fully investigated. The two BODs of the ascomycete fungus Podospora anserina were characterized by targeted gene deletions. Enzymatic assay revealed that the bod1(Δ) and bod2(Δ) mutants lost partly a thermostable laccase activity. A triple mutant inactivated for bod1, bod2 and mco, a previously investigated multicopper oxidase gene distantly related to laccases, had no thermostable laccase activity. The pattern of fruiting body production in the bod1(Δ) bod2(Δ) double mutant was changed. The bod1(Δ) and bod2(Δ) mutants were reduced in their ability to grow on ligneous and cellulosic materials. Furthermore, bod1(Δ) and bod2(Δ) mutants were defective towards resistance to phenolic substrates and H2 O2 , which may also impact lignocellulose breakdown. Double and triple mutants were more affected than single mutants, evidencing redundancy of function among BODs and mco. Overall, the data show that bod1, bod2 and mco code for non-canonical thermostable laccases that participate in the degradation of lignocellulose. Thanks to their thermal stability, these enzymes may be more promising candidate for biotechnological application than canonical laccases.
真菌对植物生物质的降解是生物燃料生产的关键步骤，漆酶是用于木质素分解的常见木质素分解酶。类胆红素氧化酶（BODs）与漆酶相关，但它们在木质纤维素降解过程中的作用尚未得到充分研究。通过靶向基因缺失对子囊菌粪生粪壳菌的两种BODs进行了表征。酶活性测定表明，bod1（Δ）和bod2（Δ）突变体部分丧失了热稳定漆酶活性。一个对bod1、bod2和mco（一个先前研究的与漆酶远缘相关的多铜氧化酶基因）失活的三重突变体没有热稳定漆酶活性。bod1（Δ）bod2（Δ）双突变体的子实体产生模式发生了变化。bod1（Δ）和bod2（Δ）突变体在木质和纤维素材料上的生长能力降低。此外，bod1（Δ）和bod2（Δ）突变体对酚类底物和H2O2的抗性存在缺陷，这也可能影响木质纤维素的分解。双突变体和三突变体比单突变体受影响更大，这证明了BODs和mco之间功能的冗余性。总体而言，数据表明bod1、bod2和mco编码参与木质纤维素降解的非典型热稳定漆酶。由于它们的热稳定性，这些酶可能比典型漆酶更有希望成为生物技术应用的候选者。
