Identification of Manganese Superoxide Dismutase from Sphingobacterium sp. T2 as a Novel Bacterial Enzyme for Lignin Oxidation.
Identification of Manganese Superoxide Dismutase from Sphingobacterium sp. T2 as a Novel Bacterial Enzyme for Lignin Oxidation.
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DOI：
10.1021/acschembio.5b00298
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发表时间：
2015-08
影响因子：
4
通讯作者：
G. M. Rashid;Charles R. Taylor;Yangqingxue Liu;Xiaoyang Zhang;D. Rea;V. Fülöp;T. Bugg
中科院分区：
文献类型：
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作者：
G. M. Rashid;Charles R. Taylor;Yangqingxue Liu;Xiaoyang Zhang;D. Rea;V. Fülöp;T. Bugg
芳香族杂聚木质素的价化是生物质生物炼油厂发展中尚未解决的重要问题，需要新型的高活性生物催化剂。木质素降解菌Sphingobacter sp.基因组DNA序列测定T2没有发现与已知的木质素降解基因匹配。在部分纯化的胞外组分中发现了两个锰超氧化物歧化酶蛋白的蛋白质组学匹配。重组MnSOD1和MnSOD2对有机溶质和硫酸盐木质素以及木质素模型化合物均表现出较高的氧化活性，并产生多种氧化产物。结构测定表明，产物为芳基-C-α和C-α-C-β键的氧化断裂和O-脱甲基化。对MnSOD1的晶体结构进行了测定，结果表明：MnSO1的晶体结构为典型的均二聚体，其中含有一个由三个His、一个Asp和一个水/氢氧化物连接的五配位的三角双锥结构的Mn(II)中心。我们认为，这些酶的木素氧化反应活性是由于产生了羟基自由基，这是一种高活性的氧化剂。这是首次证明MnSOD是一种微生物木质素氧化酶。
The valorization of aromatic heteropolymer lignin is an important unsolved problem in the development of a biomass-based biorefinery, for which novel high-activity biocatalysts are needed. Sequencing of the genomic DNA of lignin-degrading bacterial strain Sphingobacterium sp. T2 revealed no matches to known lignin-degrading genes. Proteomic matches for two manganese superoxide dismutase proteins were found in partially purified extracellular fractions. Recombinant MnSOD1 and MnSOD2 were both found to show high activity for oxidation of Organosolv and Kraft lignin, and lignin model compounds, generating multiple oxidation products. Structure determination revealed that the products result from aryl-Cα and Cα-Cβ bond oxidative cleavage and O-demethylation. The crystal structure of MnSOD1 was determined to 1.35 Å resolution, revealing a typical MnSOD homodimer harboring a five-coordinate trigonal bipyramidal Mn(II) center ligated by three His, one Asp, and a water/hydroxide in each active site. We propose that the lignin oxidation reactivity of these enzymes is due to the production of a hydroxyl radical, a highly reactive oxidant. This is the first demonstration that MnSOD is a microbial lignin-oxidizing enzyme.