Purification and cloning of a thermostable xylose (glucose) isomerase with an acidic pH optimum from Thermoanaerobacterium strain JW/SL-YS 489

The purification and characterization of an unusual xylose isomerase produced by Thermoanaerobacterium strain JW/SL-YS 489 revealed that its pH optimum is different from all other previously reported xylose isomerases. Its maximal activity is placed at pH 6.4 or pH 6.8 in a 30-minute assay, an isoelectric point at 4.7, and an estimated native molecular mass of 200 kDa, with four identical subunits of 50 kDa. It also required Mn(super 2+), Co(super 2+) or Mg(super 2+) for thermal stability and isomerase activity and preferred xylose as a substrate.