C-type cytochrome-initiated reduction of bacterial lytic polysaccharide monooxygenases.
C-type cytochrome-initiated reduction of bacterial lytic polysaccharide monooxygenases.
复制标题
DOI：
10.1042/bcj20210376
复制
发表时间：
2021-07-30
期刊：
影响因子：
--
通讯作者：
Hemsworth GR
中科院分区：
文献类型：
--
作者：
Branch J;Rajagopal BS;Paradisi A;Yates N;Lindley PJ;Smith J;Hollingsworth K;Turnbull WB;Henrissat B;Parkin A;Berry A;Hemsworth GR
从木质纤维素废物中释放出葡萄糖，随后发酵成生物燃料，这有望确保人类未来的能源需求。一组铜依赖性酶的发现被称为溶解性多糖单加氧酶（LPMO），激发了这一领域的新研究。LPMO通过氧化将链断裂引入纤维素和其他多糖中来起作用，从而增强纤维素酶作用于底物的能力。虽然有几种蛋白质被认为是真菌LPMO生物化学中的电子源，但以前没有鉴定出等同的细菌LPMO电子供体，尽管来自纤维弧菌的蛋白质Cbp 2D和E被认为是潜在的候选者。在这里，我们分析了一个小的C型细胞色素（CjX 183）存在于Cellvibrio cbp 2D，并表明它可以启动细菌铜II/I LPMO还原，也激活LPMO催化的纤维素降解。在不存在纤维素的情况下，CjX 183驱动的LPMO的还原导致从O2产生较少的H2 O2，并且相应地比当抗坏血酸盐用作还原剂时对酶的氧化损伤更少。值得注意的是，相对于使用等量的抗坏血酸盐，使用CjX 183作为活化剂保持了类似的纤维素酶增强水平。因此，我们的研究结果进一步证明了电子源的选择对LPMO作用的影响。此外，对Cbp 2D和其他类似蛋白质的研究可能会揭示细菌中多糖降解的氧化还原过程的新见解。
The release of glucose from lignocellulosic waste for subsequent fermentation into biofuels holds promise for securing humankind's future energy needs. The discovery of a set of copper-dependent enzymes known as lytic polysaccharide monooxygenases (LPMOs) has galvanised new research in this area. LPMOs act by oxidatively introducing chain breaks into cellulose and other polysaccharides, boosting the ability of cellulases to act on the substrate. Although several proteins have been implicated as electron sources in fungal LPMO biochemistry, no equivalent bacterial LPMO electron donors have been previously identified, although the proteins Cbp2D and E from Cellvibrio japonicus have been implicated as potential candidates. Here we analyse a small c-type cytochrome (CjX183) present in Cellvibrio japonicus Cbp2D, and show that it can initiate bacterial CuII/I LPMO reduction and also activate LPMO-catalyzed cellulose-degradation. In the absence of cellulose, CjX183-driven reduction of the LPMO results in less H2O2 production from O2, and correspondingly less oxidative damage to the enzyme than when ascorbate is used as the reducing agent. Significantly, using CjX183 as the activator maintained similar cellulase boosting levels relative to the use of an equivalent amount of ascorbate. Our results therefore add further evidence to the impact that the choice of electron source can have on LPMO action. Furthermore, the study of Cbp2D and other similar proteins may yet reveal new insight into the redox processes governing polysaccharide degradation in bacteria.