Biochemical characterization of a novel glucose isomerase from Anoxybacillus gonensis G2T that displays a high level of activity and thermal stability

Abstract

In the continuing search for novel enzymes suitable for the production of high fructose corn syrup (HFCS), a new glucose isomerase (GI) from the thermophile Anoxybacillus gonensis G2(T) is described. The gene encoding this GI (AgoG2GI) was cloned and then engineered for heterologous expression in Escherichia coli. The recombinant enzyme was purified from the heat treated cell-free extract by anion exchange chromatography followed by hydrophobic interaction chromatography. The purified enzyme showed optimal activity at 85 degrees C and pH 6.5. The steady state parameters of K-m and k(cat) with D-glucose were found to be 146.08 +/- 9.50 mM and 36.47 +/- 2.01 (1/s), respectively. L-arabinose, D-ribose and D-mannose also served as substrates for the enzyme with comparable kinetic parameters. AgoG2GI requires the divalent cations of Co2+, Mn2+ and Mg2+ for its maximal activity and thermostability. The results reported here are indicative of a new GI with desirable kinetics and stability parameters for the efficient production of HFCS at industrial scale. (C) 2013 Elsevier B.V. All rights reserved.