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首页> 外文期刊>Applied Microbiology >Insights into Exo- and Endoglucanase Activities of Family 6 Glycoside Hydrolases from Podospora anserina
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Insights into Exo- and Endoglucanase Activities of Family 6 Glycoside Hydrolases from Podospora anserina

机译：洞腹Po6家族糖苷水解酶的外切和内切葡聚糖酶活性的见解。

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摘要

The ascomycete Podospora anserina is a coprophilous fungus that grows at late stages on droppings of herbivores. Its genome encodes a large diversity of carbohydrate-active enzymes. Among them, four genes encode glycoside hydrolases from family 6 (GH6), the members of which comprise putative endoglucanases and exoglucanases, some of them exerting important functions for biomass degradation in fungi. Therefore, this family was selected for functional analysis. Three of the enzymes, P. anserina Cel6A ( Pa Cel6A), Pa Cel6B, and Pa Cel6C, were functionally expressed in the yeast Pichia pastoris . All three GH6 enzymes hydrolyzed crystalline and amorphous cellulose but were inactive on hydroxyethyl cellulose, mannan, galactomannan, xyloglucan, arabinoxylan, arabinan, xylan, and pectin. Pa Cel6A had a catalytic efficiency on cellotetraose comparable to that of Trichoderma reesei Cel6A ( Tr Cel6A), but Pa Cel6B and Pa Cel6C were clearly less efficient. Pa Cel6A was the enzyme with the highest stability at 45°C, while Pa Cel6C was the least stable enzyme, losing more than 50% of its activity after incubation at temperatures above 30°C for 24 h. In contrast to Tr Cel6A, all three studied P. anserina GH6 cellulases were stable over a wide range of pHs and conserved high activity at pH values of up to 9. Each enzyme displayed a distinct substrate and product profile, highlighting different modes of action, with Pa Cel6A being the enzyme most similar to Tr Cel6A. Pa Cel6B was the only enzyme with higher specific activity on carboxymethylcellulose (CMC) than on Avicel and showed lower processivity than the others. Structural modeling predicts an open catalytic cleft, suggesting that Pa Cel6B is an endoglucanase.
机译：子囊夜蛾Podospora anserina是一种共食真菌，在食草动物的粪便中生长较晚。它的基因组编码大量的碳水化合物活性酶。其中，四个基因编码家族6（GH6）的糖苷水解酶，其成员包括推定的内切葡聚糖酶和外切葡聚糖酶，其中一些对真菌中生物量的降解发挥重要作用。因此，选择该家族进行功能分析。三种酶，P。anserina Cel6A（Pa Cel6A），Pa Cel6B和Pa Cel6C在酵母毕赤酵母中功能性表达。所有这三种GH6酶均水解晶体和无定形纤维素，但对羟乙基纤维素，甘露聚糖，半乳甘露聚糖，木葡聚糖，阿拉伯木聚糖，阿拉伯聚糖，木聚糖和果胶无活性。 Pa Cel6A对纤维四糖的催化效率与里氏木霉Cel6A（Tr Cel6A）相当，但是Pa Cel6B和Pa Cel6C的效率明显较低。 Pa Cel6A是在45°C时具有最高稳定性的酶，而Pa Cel6C是最不稳定的酶，在高于30°C的温度下孵育24小时后，其活性损失超过50％。与Tr Cel6A相比，所有三种研究过的P. anserina GH6纤维素酶在很宽的pH值范围内都是稳定的，并且在高达9的pH值下都保持了高活性。每种酶均显示出不同的底物和产物谱，突出了不同的作用方式， Pa Cel6A是最类似于Tr Cel6A的酶。 Pa Cel6B是唯一一种对羧甲基纤维素（CMC）具有比Avicel更高的比活性的酶，并且其合成能力比其他酶低。结构模型预测开放的催化裂隙，表明Pa Cel6B是一种内切葡聚糖酶。

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