Sequence of thermotolerant L-rhamnose isomerase gene and use of the same

1. An isolated protein, comprising:

the amino acid sequence of SEQ ID NO: 2 and having L-rhamnose isomerase activity.

2. The isolated protein according to claim 1 ,

wherein the relative percentages of the enzymatic activities of said isolated protein against L-lyxose, L-mannose and D-allose are 23.9%, 11% and 5.5%, respectively, when the enzymatic activity of said isolated protein against L-rhamnose is 100%.

3. The isolated protein according to claim 1 ,

wherein said isolated protein has an optimal activity and stability in the pH range 6-9, and

wherein optimal enzymatic activity of said isolated protein is the highest at 80° C. in a reaction time of 10 minutes and the isolated protein is stable up to one hour at 50° C. in a solution containing 0.01 M manganese chloride and 0.5 M glycine-NaOH buffer, pH 9.0.

4. A fusion protein, comprising:

the isolated protein according to claim 1 .

5. A method for producing D-allose, comprising:

converting D-psicose to D-allose by the isomerization activity of said isolated protein of claim 1 , and

incubating said D-psicose and said isolated protein at a temperature of 35 to 80° C. in a solution containing 0.01 M manganese chloride and 0.5 M glycine-NaOH buffer, pH 9.0.