Characterization of a novel xylose isomerase from Anoxybacillus gonensis G2T

The xylA gene encoding xylose isomerase from Anoxybacillus gonensis G2^T has been cloned and successfully expressed in E. coli. Xylose isomerase was purified 10.98-fold by heat-shock and sequential column chromatography techniques to homogeneity, and the biochemical properties of the enzyme were characterized. The optimum temperature of the enzyme was 85 °C and maximum activity was observed at a pH of 6.5. Its Km and Vmax values were calculated as 25 ± 2 mM and 0.12958 ± 0.002 mumol/min/mg protein, respectively. The effects of various metal ions on the xylose isomerase were examined. Divalent cations Co^{2+}, Mg^{2+}, and Mn^{2+} were essential for xylose isomerase activity; however, bivalent metal ions (Ca^{2+}, Hg^{2+}, Ni^{2+}, Zn^{2+}, Fe^{2+}, and Cu^{2+}) showed inhibitory effects. This is the first report of characterization of the xylose isomerase of Anoxybacillus spp. According to results obtained from this study, xylose isomerase is a promising candidate for industrial applications in production of xylulose and ribose.