The present invention relates to polypeptide, preferably to a glucose isomerase, comprising an amino acid sequence, wherein the amino acid sequence of the polypeptide, preferably the glucose isomerase, is at least 95% identical to an amino acid sequence of SEQ ID NO:1, wherein the amino acid sequence of the polypeptide, preferably the glucose isomerase, comprises an amino acid substitution at one or more amino acid positions, wherein the one or more amino acid positions is/are each and independently selected from the group consisting of SEQ ID NO: 1 amino acid positions 89, 90, 95, 0, 33, 34, 35, and 59. The present invention further relates to methods preparing glucose including the use of the polypeptides of the invention for preparing glucose.