title: Cloning, expression and characterization of L-arabinose isomerase from Thermotoga neapolitana: bioconversion of D-galactose to D-tagatose using the enzyme.
abstract: Gene araA encoding an L-arabinose isomerase (AraA) from the hyperthermophile, Thermotoga neapolitana 5068 was cloned, sequenced, and expressed in Escherichia coli. The gene encoded a polypeptide of 496 residues with a calculated molecular mass of 56677 Da. The deduced amino acid sequence has 94.8% identical amino acids compared with the residues in a putative L-arabinose isomerase of Thermotoga maritima. The recombinant enzyme expressed in E. coli was purified to homogeneity by heat treatment, ion exchange chromatography and gel filtration. The thermophilic enzyme had a maximum activity of L-arabinose isomerization and D-galactose isomerization at 85 degrees C, and required divalent cations such as Co(2+) and Mn(2+) for its activity and thermostability. The apparent K(m) values of the enzyme for L-arabinose and D-galactose were 116 mM (v(max), 119 micromol min(-1) mg(-1)) and 250 mM (v(max), 14.3 micromol min(-1) mg(-1)), respectively, that were determined in the presence of both 1 mM Co(2+) and 1 mM Mn(2+). A 68% conversion of D-galactose to D-tagatose was obtained using the recombinant enzyme at the isomerization temperature of 80 degrees C.
authors.affiliation: Department of Biotechnology and Bioproducts Research Center, Yonsei University, 134 Shinchon-Dong, Sudaemun-Ku, Seoul 120-749, South Korea.
authors.forename: Byoung-Chan
authors.initials: BC
authors.lastname: Kim
authors.forename: Yoon-Hee
authors.initials: YH
authors.lastname: Lee
authors.forename: Han-Seung
authors.initials: HS
authors.lastname: Lee
authors.forename: Dong-Woo
authors.initials: DW
authors.lastname: Lee
authors.forename: Eun-Ah
authors.initials: EA
authors.lastname: Choe
authors.forename: Yu-Ryang
authors.initials: YR
authors.lastname: Pyun
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004790:Enzyme Induction; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D005690:Galactose / Q000378:metabolism*; D005816:Genetic Complementation Test; D016965:Gram-Negative Anaerobic Straight, Curved, and Helical Rods / Q000201:enzymology* / Q000235:genetics; D006601:Hexoses / Q000378:metabolism*; D006358:Hot Temperature; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D017422:Sequence Analysis, DNA
chemical_list: D006601:Hexoses; D011994:Recombinant Proteins; D019747:Aldose-Ketose Isomerases; C019715:L-arabinose isomerase; C030192:tagatose; D005690:Galactose