title: Characterization of a novel Acinetobacter baumannii xanthine dehydrogenase expressed in Escherichia coli.
abstract: OBJECTIVE
  To characterize a novel xanthine dehydrogenase (XDH) from Acinetobacter baumannii by recombinant expression in Escherichia coli and to assess its potential for industrial applications.
  
  
  RESULTS
  The XDH gene cluster was cloned from A. baumannii CICC 10254, expressed heterologously in E. coli and purified to homogeneity. The purified recombinant XDH consisted of two subunits with the respective molecular weights of 87 kDa and 56 kDa according to SDS-PAGE. XDH catalysis was optimum at pH 8.5 and 40-45 °C, was stable under alkaline conditions (pH 7-11) and the half-inactivation temperature was 60 °C. The K m, turnover number and catalytic efficiency for xanthine were 25 μM, 69 s(-1) and 2.7 μM(-1) s(-1), respectively, which is an improvement over XDHs characterized previously. A. baumannii XDH is less than 50 % identical to previously identified XDH orthologs from other species, and is the first from the Acinetobacter genus to be characterized.
  
  
  CONCLUSIONS
  The novel A. baumannii enzyme was found to be among the most active, thermostable and alkaline-tolerant XDH enzymes reported to date and has potential for use in industrial applications.
authors.affiliation: Key Laboratory for Industrial Biocatalysis, Ministry of Education of China, Institute of Biochemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing, 100084, People's Republic of China. wangchenghua@mail.tsinghua.edu.cn.
authors.forename: Cheng-Hua
authors.initials: CH
authors.lastname: Wang
authors.affiliation: Key Laboratory for Industrial Biocatalysis, Ministry of Education of China, Institute of Biochemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing, 100084, People's Republic of China. txzhao2014@sina.com.
authors.forename: Tong-Xin
authors.initials: TX
authors.lastname: Zhao
authors.affiliation: Key Laboratory for Industrial Biocatalysis, Ministry of Education of China, Institute of Biochemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing, 100084, People's Republic of China. meili2811@163.com.
authors.forename: Mei
authors.initials: M
authors.lastname: Li
authors.affiliation: Key Laboratory for Industrial Biocatalysis, Ministry of Education of China, Institute of Biochemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing, 100084, People's Republic of China. chongzhang@tsinghua.edu.cn.
authors.forename: Chong
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Key Laboratory for Industrial Biocatalysis, Ministry of Education of China, Institute of Biochemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing, 100084, People's Republic of China. xhxing@mail.tsinghua.edu.cn.
authors.forename: Xin-Hui
authors.initials: XH
authors.lastname: Xing
mesh_terms: D040981:Acinetobacter baumannii / Q000201:enzymology* / Q000235:genetics; D003001:Cloning, Molecular; D004591:Electrophoresis, Polyacrylamide Gel; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D006863:Hydrogen-Ion Concentration; D008970:Molecular Weight; D005810:Multigene Family; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013696:Temperature; D014968:Xanthine Dehydrogenase / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D021122:Protein Subunits; D011994:Recombinant Proteins; D014968:Xanthine Dehydrogenase
keywords: Acinetobacter baumannii; Alkaline tolerance; Escherichia coli; Molecular modeling; Recombinant expression; Xanthine dehydrogenase