Ketose 3-epimerase, its preparation and uses

A method for converting D- or L-ketose into the corresponding D- or L-ketose, wherein said method comprises contacting a solution containing one or more D- or L-ketoses selected from the group consisting of D-ketohexose, L-ketohexose, D-ketopentose, and L-ketopentose with a purified ketose-3-epimerase to epimerize the hydroxyl group at the C-3 position of the D- or L-ketose, thereby obtaining the corresponding D- or L-ketose, wherein said purified ketose 3-epimerase has the following substrate specificity:

• (i) epimerizing a hydroxyl group at the C-3 position of a D- or L-ketohexose to form the corresponding D- or L-ketohexose;
• (ii) epimerizing a hydroxyl group at the C-3 position of a D- or L-ketopentose to form the corresponding D- or L-ketopentose;
• and
• (iii) more readily epimerizes D-fructose to D-psicose, or vice versa, than it does D-tagatose to D-sorbose, or vice versa;
• said ketose 3-epimerase comprising an amino acid sequence which is at least 90% identical to the amino acid sequence of SEQ ID NO:
• 2.

A method for producing a D- or L-ketose, wherein said method comprises contacting a solution containing one or more D- or L-ketoses selected from the group consisting of D-ketohexose, L-ketohexose, D-ketopentose, and L-ketopentose with a purified ketose-3-epimerase to form the corresponding D- or L-ketose by epimerizing the hydroxyl group at the C-3 position of the D- or L-ketose;

• and collecting the formed D- or L-ketose, wherein said purified ketose 3-epimerase has the following substrate specificity:
• (i) epimerizing a hydroxyl group at the C-3 position of a D- or L-ketohexose to form the corresponding D- or L-ketohexose;
• (ii) epimerizing a hydroxyl group at the C-3 position of a D- or L-ketopentose to form the corresponding D- or L-ketopentose;
• and
• (iii) more readily epimerizes D-fructose to D-psicose, or vice versa, than it does D-tagatose to D-sorbose, or vice versa;
• said ketose 3-epimerase comprising an amino acid sequence which is at least 90% identical to the amino acid sequence of SEQ ID NO:
• 2.