Westereng Bjørge, Cannella David, Wittrup Agger Jane, Jørgensen Henning, Larsen Andersen Mogens, Eijsink Vincent G H, Felby Claus
Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, 1432 Ås, Norway.
University of Copenhagen, Faculty of Science, Department of Geoscience and Natural Resources Rolighedsvej 23, 1958 Frederiksberg C, Denmark.
Sci Rep. 2015 Dec 21;5:18561. doi: 10.1038/srep18561.
Enzymatic oxidation of cell wall polysaccharides by lytic polysaccharide monooxygenases (LPMOs) plays a pivotal role in the degradation of plant biomass. While experiments have shown that LPMOs are copper dependent enzymes requiring an electron donor, the mechanism and origin of the electron supply in biological systems are only partly understood. We show here that insoluble high molecular weight lignin functions as a reservoir of electrons facilitating LPMO activity. The electrons are donated to the enzyme by long-range electron transfer involving soluble low molecular weight lignins present in plant cell walls. Electron transfer was confirmed by electron paramagnetic resonance spectroscopy showing that LPMO activity on cellulose changes the level of unpaired electrons in the lignin. The discovery of a long-range electron transfer mechanism links the biodegradation of cellulose and lignin and sheds new light on how oxidative enzymes present in plant degraders may act in concert.
裂解多糖单加氧酶（LPMOs）对细胞壁多糖的酶促氧化在植物生物质降解中起关键作用。虽然实验表明LPMOs是依赖铜的酶，需要电子供体，但生物系统中电子供应的机制和来源仅得到部分理解。我们在此表明，不溶性高分子量木质素作为促进LPMO活性的电子库。电子通过涉及植物细胞壁中存在的可溶性低分子量木质素的远程电子转移提供给酶。电子顺磁共振光谱证实了电子转移，表明LPMO对纤维素的活性改变了木质素中未配对电子的水平。远程电子转移机制的发现将纤维素和木质素的生物降解联系起来，并为植物降解菌中存在的氧化酶如何协同作用提供了新的线索。
