Versatile Oxidase and Dehydrogenase Activities of Bacterial Pyranose 2-Oxidase Facilitate Redox Cycling with Manganese Peroxidase In Vitro
Versatile Oxidase and Dehydrogenase Activities of Bacterial Pyranose 2-Oxidase Facilitate Redox Cycling with Manganese Peroxidase In Vitro
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DOI：
10.1128/aem.00390-19
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发表时间：
2019-07-01
影响因子：
4.4
通讯作者：
Peterbauer, Clemens K.
中科院分区：
文献类型：
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作者：
Herzog, Peter L.;Suetzl, Leander;Peterbauer, Clemens K.
吡喃糖2-氧化酶（POx）长期以来一直被认为是木质素降解的生理作用，但证据提供的生化机制和相互作用的见解是不够的。有大量的数据在文献中的氧化酶和脱氢酶活性的POx，但这种双重性的生物相关性不能最终确定。在这里，我们提出了一个全面的生物化学和系统发育特征的一种新的吡喃糖2-氧化酶从放线菌细菌Kitasatospora aureofaciens（KaPOx），以及一个可能的生物分子协同作用，这种酶与过氧化物酶在体外使用酚类模型底物。真菌和细菌推定的POx编码序列的系统发育分析揭示了它们之间的密切进化关系，并支持祖先POx序列的晚期水平基因转移。我们成功地表达并鉴定了一个新的细菌POx基因。aureofaciens，其中一个推定的POx基因密切相关的著名真菌POx基因。其生化特性符合已知真菌吡喃糖2-氧化酶的大多数经典标志，即，与作为电子供体的一系列不同单糖的反应性以及与作为电子受体的氧、各种醌和络合金属离子的活性。因此，KaPOx显示出与真菌POx类似的明显的氧化酶和脱氢酶二元性。我们进一步在KaPOx和锰过氧化物酶（MnP）之间进行了芳香族木质素模型化合物的有效氧化还原循环。此外，我们发现了锰（III）的还原活性KaPOx，这意味着它的能力，提供H2 O2相结合，这可能是其他POx作为补充的酶促工具氧化木质素降解由专门的peroxidases.IMPORTANCE吡喃糖氧化酶和（锰）过氧化物酶之间的协同机制的建立是阐明微生物木质素降解过程中的一个重要步骤。在这里，一个细菌吡喃糖2-氧化酶的全面表征从Kitasatospora aureofaciens是特别感兴趣的几个原因。首先，假定的吡喃糖氧化酶基因的系统发育分析揭示了细菌中广泛存在的高度相似的酶。尽管如此，只有一份关于细菌吡喃糖氧化酶的报告，强调需要在科学文献中缩小这一差距。此外，相对较小的K. aureofaciens蛋白质组被认为提供了一组有限的酶功能，以实现木质纤维素生物质降解。因此，酶和生物体都提出了一个可行的模型来研究细菌木质素分解的机制，阐明与专门的过氧化物酶的生理相关的相互作用，并可能实现生物技术应用。
Pyranose 2-oxidase (POx) has long been accredited a physiological role in lignin degradation, but evidence to provide insights into the biochemical mechanisms and interactions is insufficient. There are ample data in the literature on the oxidase and dehydrogenase activities of POx, yet the biological relevance of this duality could not be established conclusively. Here we present a comprehensive biochemical and phylogenetic characterization of a novel pyranose 2-oxidase from the actinomycetous bacterium Kitasatospora aureofaciens (KaPOx) as well as a possible biomolecular synergism of this enzyme with peroxidases using phenolic model substrates in vitro. A phylogenetic analysis of both fungal and bacterial putative POx-encoding sequences revealed their close evolutionary relationship and supports a late horizontal gene transfer of ancestral POx sequences. We successfully expressed and characterized a novel bacterial POx gene from K. aureofaciens, one of the putative POx genes closely related to well-known fungal POx genes. Its biochemical characteristics comply with most of the classical hallmarks of known fungal pyranose 2-oxidases, i.e., reactivity with a range of different monosaccharides as electron donors as well as activity with oxygen, various quinones, and complexed metal ions as electron acceptors. Thus, KaPOx shows the pronounced duality of oxidase and dehydrogenase similar to that of fungal POx. We further performed efficient redox cycling of aromatic lignin model compounds between KaPOx and manganese peroxidase (MnP). In addition, we found a Mn(III) reduction activity in KaPOx, which, in combination with its ability to provide H2O2, implies this and potentially other POx as complementary enzymatic tools for oxidative lignin degradation by specialized peroxidases.IMPORTANCE Establishment of a mechanistic synergism between pyranose oxidase and (manganese) peroxidases represents a vital step in the course of elucidating microbial lignin degradation. Here, the comprehensive characterization of a bacterial pyranose 2-oxidase from Kitasatospora aureofaciens is of particular interest for several reasons. First, the phylogenetic analysis of putative pyranose oxidase genes reveals a widespread occurrence of highly similar enzymes in bacteria. Still, there is only a single report on a bacterial pyranose oxidase, stressing the need of closing this gap in the scientific literature. In addition, the relatively small K. aureofaciens proteome supposedly supplies a limited set of enzymatic functions to realize lignocellulosic biomass degradation. Both enzyme and organism therefore present a viable model to study the mechanisms of bacterial lignin decomposition, elucidate physiologically relevant interactions with specialized peroxidases, and potentially realize biotechnological applications.