title: Substrate-binding specificity of chitinase and chitosanase as revealed by active-site architecture analysis.
abstract: Chitinases and chitosanases, referred to as chitinolytic enzymes, are two important categories of glycoside hydrolases (GH) that play a key role in degrading chitin and chitosan, two naturally abundant polysaccharides. Here, we investigate the active site architecture of the major chitosanase (GH8, GH46) and chitinase families (GH18, GH19). Both charged (Glu, His, Arg, Asp) and aromatic amino acids (Tyr, Trp, Phe) are observed with higher frequency within chitinolytic active sites as compared to elsewhere in the enzyme structure, indicating significant roles related to enzyme function. Hydrogen bonds between chitinolytic enzymes and the substrate C2 functional groups, i.e. amino groups and N-acetyl groups, drive substrate recognition, while non-specific CH-π interactions between aromatic residues and substrate mainly contribute to tighter binding and enhanced processivity evident in GH8 and GH18 enzymes. For different families of chitinolytic enzymes, the number, type, and position of substrate atoms bound in the active site vary, resulting in different substrate-binding specificities. The data presented here explain the synergistic action of multiple enzyme families at a molecular level and provide a more reasonable method for functional annotation, which can be further applied toward the practical engineering of chitinases and chitosanases.
authors.affiliation: Taishan College, Shandong University, Jinan 250100, China.
authors.forename: Shijia
authors.initials: S
authors.lastname: Liu
authors.affiliation: Taishan College, Shandong University, Jinan 250100, China.
authors.forename: Shangjin
authors.initials: S
authors.lastname: Shao
authors.affiliation: Taishan College, Shandong University, Jinan 250100, China.
authors.forename: Linlin
authors.initials: L
authors.lastname: Li
authors.affiliation: Taishan College, Shandong University, Jinan 250100, China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Cheng
authors.affiliation: The State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, China.
authors.forename: Li
authors.initials: L
authors.lastname: Tian
authors.affiliation: The State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, China.
authors.forename: Peiji
authors.initials: P
authors.lastname: Gao
authors.affiliation: The State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, China. Electronic address: lswang@sdu.edu.cn.
authors.forename: Lushan
authors.initials: L
authors.lastname: Wang
mesh_terms: D001665:Binding Sites; D002236:Carbohydrate Conformation; D002688:Chitinases / Q000737:chemistry* / Q000378:metabolism*; D019295:Computational Biology; D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D006026:Glycoside Hydrolases; C019868:chitosanase; D002688:Chitinases
keywords: Active-site architecture; Chitinase; Chitosanase; Substrate-binding specificity