Competitive Sorption Kinetics of Inhibited Endo- and Exoglucanases on a Model Cellulose Substrate
Competitive Sorption Kinetics of Inhibited Endo- and Exoglucanases on a Model Cellulose Substrate
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DOI：
10.1021/la3024524
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发表时间：
2012-10-16
期刊：
影响因子：
3.9
通讯作者：
Radke, Clayton J.
中科院分区：
文献类型：
--
作者：
Maurer, Samuel A.;Bedbrook, Claire N.;Radke, Clayton J.
首次研究了来自 T. longibrachiatum 的受抑制纤维二糖水解酶 I（Cel7A，一种外切葡聚糖酶）和内切葡聚糖酶 I（Cel7B）在纤维素上的竞争吸附。使用石英晶体微重分析 (QCM)，测量各种类型的纤维素酶及其混合物在模型纤维素表面的吸附和解吸的吸附历史。我们发现 Cel7A 对纤维素的吸附亲和力比 Cel7B 更高。两种纤维素酶的吸附在 30-60 分钟的时间范围内变得不可逆，这比通常用于工业纤维素水解的时间范围要短得多。提出了包含一阶不可逆结合的多组分朗缪尔动力学模型。尽管两种酶的吸附和解吸速率常数不同，但每种表面酶不可逆结合的速率是相同的。由于 Cel7A 对纤维素表面的亲和力较高，当 Cel7A 和 Cel7B 竞争表面位点时，需要显着更高的 Cel7B 体积浓度才能达到相当的表面酶浓度。由于纤维素解构显着受益于纤维素表面上内切葡聚糖酶和纤维二糖水解酶的协同活性，因此考虑竞争性吸附对于开发有效的纤维素酶混合物至关重要。
For the first time, the competitive adsorption of inhibited cellobiohydrolase I (Cel7A, an exoglucanase) and endoglucanase I (Cel7B) from T. longibrachiatum is studied on cellulose. Using quartz crystal microgravimetry (QCM), sorption histories are measured for individual types of cellulases and their mixtures adsorbing to and desorbing from a model cellulose surface. We find that Cel7A has a higher adsorptive affinity for cellulose than does Cel7B. The adsorption of both cellulases becomes irreversible on time scales of 30-60 min, which are much shorter than those typically used for industrial cellulose hydrolysis. A multicomponent Langmuir kinetic model including first-order irreversible binding is proposed. Although adsorption and desorption rate constants differ between the two enzymes, the rate at which each surface enzyme irreversibly binds is identical. Because of the higher affinity of Cel7A for the cellulose surface, when Cel7A and Cel7B compete for surface sites, a significantly higher bulk concentration of Cel7B is required to achieve comparable surface enzyme concentrations. Because cellulose deconstruction benefits significantly from the cooperative activity of endoglucanases and cellobiohydrolases on the cellulose surface, accounting for competitive adsorption is crucial to developing effective cellulase mixtures.