Starch-degrading enzymes from the brown-rot fungus Fomitopsis palustris
Starch-degrading enzymes from the brown-rot fungus Fomitopsis palustris
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DOI：
10.1016/j.pep.2020.105609
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发表时间：
2020-06-01
影响因子：
1.6
通讯作者：
Habu, Naoto
中科院分区：
文献类型：
--
作者：
Tanaka, Yuki;Konno, Naotake;Habu, Naoto
褐腐菌优先降解软木，并导致木质结构的严重破坏。在褐腐腐烂的初期，在射线薄壁组织中观察到真菌的穿透菌丝。由于淀粉粒是已知的存在于射线薄壁组织的边材，淀粉降解酶的功能和作用的调查是重要的，以了解褐腐腐烂的初始阶段。我们从褐腐真菌沼泽拟层孔菌中分离纯化了两种淀粉降解酶，即α-淀粉酶（FpAmy 13 A）和葡糖淀粉酶（FpGLA 15 A），并克隆了相应的基因。两种酶的最适反应温度均为60 ℃。FpAmy 13 A在2.0 - 5.0的宽pH范围内显示出较高的活性，而FpGLA 15 A在pH 5.0-6.0下最具活性。发现FpGLA 15 A具有显著的热稳定性。即使在pH 7.0的磷酸钠缓冲液中于100 ℃处理30分钟后，仍保留约25%的活性。这些不同的特性暗示了这些酶在木材淀粉降解中的不同作用。
Brown-rot fungi preferentially degrade softwood and cause severe breakdown of wooden structures. At the initial stage of the brown-rot decay, penetrating hyphae of the fungi are observed in ray parenchyma. Since starch grains are known to be present in the ray parenchyma of sapwood, investigation of the functions and roles of the starch-degrading enzymes is important to understand the initial stage of brown-rot decay. We purified and characterized two starch-degrading enzymes, an alpha-amylase (FpAmy13A) and a glucoamylase (FpGLA15A), from the brown-rot fungus, Fomitopsis palustris, and cloned the corresponding genes. The optimal temperature for both enzymes was 60 degrees C. FpAmy13A showed higher activity at a broad range of pH from 2.0 to 5.0, whereas FpGLA15A was most active at pH 5.0-6.0. Notable thermal stability was found for FpGLA15A. Approximately 25% of the activity remained even after treatment at 100 degrees C for 30 min in sodium phosphate buffer at pH 7.0. These different characteristics imply the different roles of these enzymes in the starch degradation of wood.