title: Structural and biochemical insights into the degradation mechanism of chitosan by chitosanase OU01.
abstract: BACKGROUND
  A detailed knowledge about the degradation mechanism of chitosanase hydrolysis is critical for the design of novel enzymes to produce well-defined chito-oligosaccharide products.
  
  
  METHODS
  Through the combination of structural and biochemical analysis, we present new findings that provide novel insights into the degradation mechanism of chitosanase OU01.
  
  
  RESULTS
  We have determined the crystal structure of Asp(43)/Ala mutant of OU01, and have trapped the hydrolyzed product of the reaction. This structure reveals the role of the general acid (Glu(25)) in catalysis. Two structural features about the mechanisms of the non-processive chitosanases are described for the first time. 1). Structural comparison reveals that the enzyme goes through an open-closed-open conformational transition upon substrate binding and product release; 2). polar residues constitute the substrate binding cleft. Additional site important for polymeric substrate recognition is identified and a three-step polymeric substrate recognition mechanism is proposed.
  
  
  CONCLUSIONS
  Detailed substrate recognition mechanism is described for non-processive chitosanase for the first time.
  
  
  CONCLUSIONS
  These findings provide new structural insights into the understanding of overall hydrolysis mechanism for non-processive chitosanase, and also will facilitate the design of new enzymes used for industrial purpose.
authors.affiliation: College of Marine Life Sciences, Ocean University of China, Qingdao, China.
authors.forename: Qianqian
authors.initials: Q
authors.lastname: Lyu
authors.affiliation: Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Shi
authors.affiliation: Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao, China.
authors.forename: Song
authors.initials: S
authors.lastname: Wang
authors.affiliation: College of Marine Life Sciences, Ocean University of China, Qingdao, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Yang
authors.affiliation: College of Marine Life Sciences, Ocean University of China, Qingdao, China.
authors.forename: Baoqin
authors.initials: B
authors.lastname: Han
authors.affiliation: College of Marine Life Sciences, Ocean University of China, Qingdao, China.
authors.forename: Wanshun
authors.initials: W
authors.lastname: Liu
authors.affiliation: Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA.
authors.forename: David N M
authors.initials: DN
authors.lastname: Jones
authors.affiliation: College of Marine Life Sciences, Ocean University of China, Qingdao, China. Electronic address: liuweizhi@ouc.edu.cn.
authors.forename: Weizhi
authors.initials: W
authors.lastname: Liu
mesh_terms: D055162:Biocatalysis; D048271:Chitosan / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D017434:Protein Structure, Tertiary
chemical_list: D048271:Chitosan; D006026:Glycoside Hydrolases; C019868:chitosanase
keywords: Chitosan; Degradation; Glycoside hydrolysis; Mutagenesis; X-ray crystallography