Glucose isomerases

A glucose isomerase comprising an amino acid sequence having at least 80% identity to SEQ ID NO:

• 1 and comprising at least one substitution selected from the group consisting of V187C, V187T, F242C, P313S, and A47S,
• wherein the glucose isomerase has at least one of characteristics (A), (B), (C), (D) and (E), or any combination thereof,
• wherein
• characteristic (A) is an increased enzymatic activity in the absence of Ca2+ (A0) in comparison to SEQ ID NO:1 with respect to the conversion of fructose into glucose or vice versa;
• characteristic (B) is an increased enzymatic activity in the presence of Ca2+ (ACa2+) in comparison to SEQ ID NO:
• 1 with respect to the conversion of fructose into glucose or vice versa;
• characteristic (C) is an increased residual enzymatic activity in the presence of Ca2+ (RACa2+) in comparison to SEQ ID NO:1 with respect to the conversion of fructose into glucose or vice versa;
• characteristic (D) is an increased enzymatic activity at neutral and acidic pH (ApH) in comparison to SEQ ID NO:
• 1 with respect to the conversion of fructose into glucose or vice versa;
• and
• characteristic (E) is an increased enzymatic activity at low temperatures (ATemp) in comparison to SEQ ID NO:1 with respect to the conversion of fructose into glucose or vice versa.