Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, Department of Microbiology, College of Life Sciences, Nanjing Agricultural University, Nanjing, 210095, Jiangsu, P. R. China.
World J Microbiol Biotechnol. 2022 Jan 6;38(2):32. doi: 10.1007/s11274-021-03216-x.
Ganoderma lucidum is a representative white-rot fungus that has great potential to degrade lignocellulose biomass. Laccase is recognized as a class of the most important lignin-degrading enzymes in G. lucidum. However, the comprehensive regulatory mechanisms of laccase are still lacking. Based on the genome sequence of G. lucidum, 15 laccase genes were identified and their encoding proteins were analyzed in this study. All of the laccase proteins are predicted to be multicopper oxidases with conserved copper-binding domains. Most laccase proteins were secreted enzymes in addition to Lac14 in which the signal peptide could not be predicted. The activity of all laccases showed the highest level at pH 3.0 or pH 7.0, with total laccase activity of approximately 200 U/mg protein. Silencing PacC resulted in a 5.2 fold increase in laccase activity compared with WT. Five laccase genes (lac1, lac6, lac9, lac10 and lac14) showed an increased transcription levels (approximately 1.5-5.6 fold) in the PacC-silenced strains versus that in WT, while other laccase genes were downregulated or unchanged. The extracellular pH value was about 3.1, which was more acidic in the PacC-silenced strains than in the WT (pH 3.5). Moreover, maintaining the fermentation pH resulted in a downregulation of laccase activity which is induced by silencing PacC. Our findings indicate that in addition to its function in acidification of environmental pH, PacC plays an important role in regulating laccase activity in fungi.
灵芝是一种有代表性的白腐真菌，具有很大的降解木质纤维素生物质的潜力。漆酶被认为是灵芝中最重要的一类木质素降解酶。然而，漆酶的综合调控机制仍然缺乏。本研究基于灵芝的基因组序列，鉴定了 15 个漆酶基因，并对其编码蛋白进行了分析。所有漆酶蛋白均预测为多铜氧化酶，具有保守的铜结合结构域。除了 Lac14 之外，大多数漆酶蛋白都是分泌酶，无法预测信号肽。所有漆酶的活性在 pH3.0 或 pH7.0 时达到最高水平，总漆酶活性约为 200U/mg 蛋白。与 WT 相比，沉默 PacC 可使漆酶活性增加 5.2 倍。与 WT 相比，沉默 PacC 后，5 个漆酶基因（lac1、lac6、lac9、lac10 和 lac14）的转录水平增加了约 1.5-5.6 倍，而其他漆酶基因则下调或不变。胞外 pH 值约为 3.1，在 PacC 沉默菌株中比在 WT 中更酸性（pH3.5）。此外，维持发酵 pH 值会导致 PacC 沉默诱导的漆酶活性下调。我们的研究结果表明，除了在酸化环境 pH 值方面的作用外，PacC 在真菌中调节漆酶活性方面也起着重要作用。
