细菌几丁质酶结构、功能及分子设计的研究进展

几丁质是仅次于纤维素的第二大天然多糖,由N-乙酰-D-氨基葡萄糖聚合而成,具有重要的应用价值。自然界中几丁质可被细菌高效降解。细菌可分泌多种几丁质降解酶类,主要分布在GH18家族和GH19家族中。细菌中几丁质降解酶基因存在明显的基因扩增及多结构域组合现象,不同家族、不同作用模式的几丁质酶系协同作用打破复杂的抗降解屏障,完成结晶几丁质的高效降解。因此,深入分析细菌几丁质酶结构与功能,对几丁质高效降解与高值转化应用具有重要意义。本文介绍了细菌几丁质酶的分类、结构特点与催化作用机制;总结了不同细菌胞外几丁质降解酶系的协同降解模式;针对几丁质酶家族分子改造的研究进展,展望了以结构生物信息学及大数据深度学习为基础的蛋白质工程设计策略在今后改造中的作用,为几丁质酶的设计与理性改造提供新的视角与思路。

Research Progress on Structure, Function and Molecular Design of Bacterial Chitinase

Chitin is the second largest natural polysaccharide after cellulose, which is polymerized by N-acetyl-D-glucosamine, having important application value in agriculture, industry, medical treatment and other fields. Natural chitin exists in a highly crystalline state with complex barrier against degradation. Bacteria can secrete multiple chitinases with special functions to degrade chitin efficiently. Chitinases mainly distributed in GH18 and GH19 families in CAZy database. There are obvious phenomena of gene amplification and multi-domain combination of chitinase genes in bacteria. Chitinases with various action modes in different GH families can act synergistically to break the barrier and complete efficient degradation of crystalline chitin. Therefore, in-depth analysis of the structure and function of bacterial chitinase is of great significance for efficient degradation and high-value conversion of chitin. In this paper, the classification and structural characteristics of bacterial chitinase were introduced, which laid a foundation for further research on the functional mechanism of the enzyme. After that, the action mechanism of chitinases belong to GH18 and GH19 families, including the binding mechanism of enzyme to substrate, catalytic mechanism was summarized to further understand the characteristics of chitinase at molecular level. It is worth noting that processibility is an important characteristic of chitinase to efficiently degrade crystalline chitin, so the molecular mechanism of chitinases, including the effects of polar amino acid residues and aromatic residues on processibility was focused on. In addition, the synergistic degradation modes of extracellular chitin degradation enzymes in 3 different bacterial were summarized, which provided a theoretical basis for the design of efficient chitin degradation enzymes. Through a review of the research progress of molecular modification of chitinases, the role of protein engineering design strategy based on structural bioinformatics and big data deep learning in future modification is prospected, which provides a new perspective and ideas for the design and rational modification of chitinase. To sum up, this paper introduces the relative knowledge of chitinase from structure to mechanism and function to application, which provides a comprehensive foundation for further study of chitinase, the structural and molecular basis for the design of high-functional enzyme, and a theoretical basis for the application of chitinase.