Department of Mycology, Shandong Agricultural University, Taian, Shandong, 271018, China.
Microb Cell Fact. 2022 Mar 12;21(1):38. doi: 10.1186/s12934-022-01767-8.
Lytic polysaccharide monooxygenases (LPMOs) belonging to the auxiliary activity 9 family (AA9) are widely found in aerobic fungi. These enzymes are O-dependent copper oxidoreductases that catalyze the oxidative cleavage of cellulose. However, studies that have investigated AA9 LPMOs of aerobic fungi in the herbivore gut are scare. To date, whether oxidative cleavage of cellulose occurs in the herbivore gut is unknown.
We report for the first time experimental evidence that AA9 LPMOs from aerobic thermophilic fungi catalyze the oxidative cleavage of cellulose present in the horse gut to C1-oxidized cellulose and C1- and C4-oxidized cello-oligosaccharides. We isolated and identified three thermophilic fungi and measured their growth and AA9 LPMO expression at 37 °C in vitro. We also assessed the expression and the presence of AA9 LPMOs from thermophilic fungi in situ. Finally, we used two recombinant AA9 LPMOs and a native AA9 LPMO from thermophilic fungi to cleave cellulose to yield C1-oxidized products at 37 °C in vitro.
The oxidative cleavage of cellulose occurs in the horse gut. This finding will broaden the known the biological functions of the ubiquitous LPMOs and aid in determining biological significance of aerobic thermophilic fungi.
属于辅助活性 9 家族（AA9）的溶细胞多糖单加氧酶（LPMOs）广泛存在于需氧真菌中。这些酶是 O 依赖型铜氧化还原酶，可催化纤维素的氧化裂解。然而，关于食草动物肠道中需氧真菌 AA9 LPMO 的研究却很少。迄今为止，尚不清楚纤维素的氧化裂解是否发生在食草动物肠道中。
我们首次报道实验证据表明，来自好氧嗜热真菌的 AA9 LPMO 可催化马肠道中存在的纤维素发生氧化裂解，生成 C1 氧化纤维素和 C1 和 C4 氧化的纤维寡糖。我们分离并鉴定了三种嗜热真菌，并在体外 37°C 下测量了它们的生长和 AA9 LPMO 的表达情况。我们还评估了嗜热真菌的 AA9 LPMO 的表达和存在情况。最后，我们使用两种重组 AA9 LPMO 和一种来自嗜热真菌的天然 AA9 LPMO 在体外 37°C 下切割纤维素，生成 C1 氧化产物。
纤维素的氧化裂解发生在马的肠道中。这一发现将拓宽普遍存在的 LPMO 的已知生物学功能，并有助于确定好氧嗜热真菌的生物学意义。
