Expression and Characterization of a Thermostable Glucose Isomerase from the Hyperthermophile, Thermotoga maritima

Abstract:

The glucose isomerase produced from Thermotoga maritima, a hyperthermophilic anaerobic bacterium, has a large potential in industrial application because of its excellent thermostability. T. maritima can only produce small amount glucose isomerase since the rigorous cultivation conditions. The gene xylA encoding glucose isomerase from T. maritima MSB8 were cloned and expressed in Escherichia coli JM109 using a heat-shock expression vector pHsh. The recombinant glucose isomerase was purified 8.02-fold from the E. coli JM109 recombinant with a recovery of 49.02% using heat treatment and ion exchange chromatography, to give a single band on SDS-PAGE. The optimum pH and temperature of the enzyme were found to be pH 7.0 and 95°C. The enzyme was stable in the range pH 6~9, and showed a half-life of over 5 h at 95°C. The enzyme activity was activated with 5mmol/L Mg2+ and Co2+. The apparent Km and Vmax values for glucose were 105 mmol/L and 45.2 mol/(min×mg), respectively.

Key words:Glucose isomerase, Thermotoga maritima, Expression, Characterization