Journal Article

Cloning, expression and characterization of <span class="smallCaps">l</span>-arabinose isomerase from <i>Thermotoga neapolitana</i>: bioconversion of <span class="smallCaps">d</span>-galactose to <span class="smallCaps">d</span>-tagatose using the enzyme

Byoung-Chan Kim, Yoon-Hee Lee, Han-Seung Lee, Dong-Woo Lee, Eun-Ah Choe and Yu-Ryang Pyun

in FEMS Microbiology Letters

Volume 212, issue 1, pages 121-126
Published in print June 2002 |
Published online January 2006 | e-ISSN: 1574-6968 | DOI:

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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 56 677 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°C, and required divalent cations such as Co2+ and Mn2+ for its activity and thermostability. The apparent Km values of the enzyme for l-arabinose and d-galactose were 116 mM (vmax, 119 μmol min−1 mg−1) and 250 mM (vmax, 14.3 μmol min−1 mg−1), respectively, that were determined in the presence of both 1 mM Co2+ and 1 mM Mn2+. A 68% conversion of d-galactose to d-tagatose was obtained using the recombinant enzyme at the isomerization temperature of 80°C.

Keywords: l-Arabinose isomerase; Thermotoga neapolitana; d-Tagatose

Journal Article.  2757 words.  Illustrated.

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