Lytic polysaccharide monooxygenases (LPMOs) are copper‐center enzymes that are involved in the oxidative cleavage of the glycosidic bond in crystalline cellulose and other polysaccharides. The LPMO reaction is initiated by the addition of a reductant and oxygen to ultimately form an unknown activated copper–oxygen species that is responsible for polysaccharide‐substrate H‐atom abstraction. Given the sensitivity of metalloproteins to radiation damage, neutron protein crystallography provides a nondestructive technique for structural characterization while also informing on the positions of H atoms. Neutron cryo‐crystallography permits the trapping of catalytic intermediates, thereby providing insight into the protonation states and chemical nature of otherwise short‐lived species in the reaction mechanism. To characterize the reaction‐mechanism intermediates of LPMO9D from Neurospora crassa, a cryo‐neutron diffraction data set was collected from an ascorbate‐reduced crystal. A second neutron diffraction data set was collected at room temperature from an LPMO9D crystal exposed to low‐pH conditions to probe the protonation states of ionizable groups involved in catalysis under acidic conditions.

中文翻译：

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还原和酸性条件下裂解多糖单加氧酶的中子和 X 射线衍射数据收集的初步结果

裂解多糖单加氧酶（LPMO）是铜中心酶，参与结晶纤维素和其他多糖中糖苷键的氧化裂解。LPMO 反应是通过添加还原剂和氧气来引发的，最终形成一种未知的活化铜氧物质，该物质负责多糖底物 H 原子的提取。鉴于金属蛋白对辐射损伤的敏感性，中子蛋白晶体学为结构表征提供了一种无损技术，同时还提供了氢原子的位置信息。中子冷冻晶体学可以捕获催化中间体，从而深入了解反应机制中其他寿命较短的物质的质子化状态和化学性质。为了表征粗糙脉孢菌LPMO9D 的反应机制中间体，从抗坏血酸还原晶体中收集了低温中子衍射数据集。第二个中子衍射数据集是在室温下从暴露于低 pH 条件的 LPMO9D 晶体中收集的，以探测酸性条件下参与催化的可电离基团的质子化状态。