title: Implication of a galactomannan-binding GH2 β-mannosidase in mannan utilization by Caldicellulosiruptor bescii.
abstract: Many glycoside hydrolases involved in deconstruction of cellulose and xylan from the excellent plant cell wall polysaccharides-degrader Caldicellulosiruptor bescii have been cloned and analyzed. However, far less is known about the enzymatic breakdown of mannan, an important component of hemicellulose. We herein cloned, expressed and purified the first β-mannosidase CbMan2A from C. bescii. CbMan2A is thermophilic, with an optimal temperature of 80 °C. CbMan2A hydrolyzes mannooligosaccharides with degrees of polymerization from 2 to 6 mainly into mannose and shows strong synergy with CbMan5A, an endo-mannanase from the same bacterium, in releasing mannose from β-1,4-mannan. Thus CbMan2A forms the missing link in enzymatic conversion of mannan into the ready-to-use mannose by C. bescii. Based on these observations, a model illustrating how CbMan2A may assist C. bescii in mannan utilization is presented. In addition, CbMan2A appeared to bind to insoluble galactomannan in a pH-dependent fashion. Although the relation of this feature to mannan utilization remains elusive, CbMan2A represents an excellent model for investigation of the binding of GH2 β-mannosidases to galactomannan.
authors.affiliation: College of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083, PR China; Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, PR China.
authors.forename: Di
authors.initials: D
authors.lastname: Liang
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, PR China.
authors.forename: Li
authors.initials: L
authors.lastname: Gong
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, PR China.
authors.forename: Bin
authors.initials: B
authors.lastname: Yao
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, PR China.
authors.forename: Xianli
authors.initials: X
authors.lastname: Xue
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, PR China.
authors.forename: Xing
authors.initials: X
authors.lastname: Qin
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, PR China.
authors.forename: Rui
authors.initials: R
authors.lastname: Ma
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, PR China.
authors.forename: Huiying
authors.initials: H
authors.lastname: Luo
authors.affiliation: College of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083, PR China. Electronic address: xiexiangm@bjfu.edu.cn.
authors.forename: Xiangming
authors.initials: X
authors.lastname: Xie
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, PR China. Electronic address: suxiaoyun@caas.cn.
authors.forename: Xiaoyun
authors.initials: X
authors.lastname: Su
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D000068536:Bacillota / Q000737:chemistry* / Q000201:enzymology; D005690:Galactose / Q000031:analogs & derivatives; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D008351:Mannans / Q000737:chemistry* / Q000378:metabolism; D008358:Mannose / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013696:Temperature; D044902:beta-Mannosidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D008351:Mannans; C081692:beta-1,4-mannan; C012990:galactomannan; D044902:beta-Mannosidase; D008358:Mannose; D005690:Galactose
keywords: Caldicellulosiruptor bescii; Consolidated bioprocessing; GH2; Glycoside hydrolase; Mannosidase