Qingdao Energy Institute reveals the thermoadaptability of glycoside hydrolase
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It is generally believed that the binding of carbohydrate-binding modules (CBMs) to polysaccharide substrates can improve the catalytic ability of the enzyme through orientation effects and proximity effects. Researchers have conducted extensive research on CBMs, but their effects on the catalytic properties and thermal stability of glycoside hydrolases have not been clearly defined.
Recently, Li Welfare Team, Researcher of the Microbial Resources Team of the Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, and Wang Lushan, a professor at Shandong University, collaborated on glycoside hydrolase (GH) derived from the extreme thermophilic anaerobic bacteria Caldicellulosiruptor sp. F3211. Family xylanase and GH10 family xylanase were used as research objects. The effects of CBMs on the thermal stability of lignocellulosic enzymes were systematically analyzed, and the thermal adaptive evolution mechanism of multi-module cellulases was proposed and enriched. Related results were recently published online at Appl Environ Microbiol (Meng, et al, Appl Environ Microbiol, 2015, 81(6): 2006-2014).
Studies have found that CBMs have a decisive effect on the thermal stability of xylanase. Deletion of the GH11 family xylanase CBMs resulted in increased protein thermal stability, while deletion of the GH10 family xylanase CBMs reduced the thermal stability of the enzyme. Through homology modeling and isothermal titration calorimetry experiments, it was found that the heat resistance of xylanase depends not only on the properties of individual modules, but also on the interactions between modules within the protein; further verification of the inference through chemical cross-linking experiments , to prove whether there is interaction between the modules determines the effect of CBMs on the thermal stability of xylanase.
By analyzing Linker sequences of multiple GH10 and GH11 family xylanases, the GH11 family xylanase linker was found to have high serine and threonine content, or proline content. Therefore, the linker has a strong rigidity, resulting in the protein adopting an extended conformation, thereby determining that the GH11 family xylanase does not have inter-module interactions. The thermal stability of multi-module glycoside hydrolase is the result of the co-evolution of amino acid sequences and non-covalent interactions between modules. The balance between the rigidity of the overall protein structure and the flexibility of the catalytic center together determines the thermal stability of the enzyme.
The above research was supported by the "973" plan of the Ministry of Science and Technology and the National Natural Science Foundation.
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