The present invention provides novel isolated polynucleotides encoding a novel xylose isomerases capable of catalyzing the conversion of glucose to fructose and nucleic acids encoding for such isomerase. The present invention also provides a method of producing the xylose isomerase enzymes employing DNA encoding for the enzymes, plasmids containing the DNA, and bacteria into which the plasmids have been inserted and which produce the enzymes.
1. An isolated nucleic acid molecule with a nucleotide sequence encoding a polypeptide with glucose isomerase activity comprising the amino acid sequence of SEQ ID NO:2 with two or more amino acid residue changes selected from the group consisting of V186T, L283P, and F187S.
2. The nucleic acid molecule of claim 1 wherein the nucleic acid molecule encodes a polypeptide comprising the amino acid sequence of SEQ ID NO:11.
3. The nucleic acid molecule of claim 1 , wherein the nucleic acid molecule encodes a polypeptide comprising the amino acid sequence of amino acids 2–444 of SEQ ID NO:4.
4. The nucleic acid molecule of claim 1 , wherein the nucleic acid molecule comprises the nucleic acid sequence of nucleotides 616–1950 of SEQ ID NO:3 or SEQ ID NO:12.
5. A vector comprising the nucleic acid molecule of claim 1 .
6. A vector according to claim 5 wherein the vector is selected from the group consisting of a plasmid, virus, and bacteriophage.
7. A vector according to claim 6 , wherein the isolated nucleic acid molecule is inserted into the vector in proper orientation and correct reading frame and wherein the isolated nucleic acid molecule is operatively linked to a promoter sequence such that a cell transformed with the vector expresses a polypeptide with glucose isomerase activity comprising the amino acid sequence of SEQ ID NO:11 or amino acids 2–444 of SEQ ID NO:4.
8. An isolated host cell transformed with the vector of claim 7 .
9. A process for producing the polypeptide comprising the amino acid sequence of SEQ ID NO:11 or amino acids 2–444 of SEQ ID NO:4 having glucose isomerase activity comprising:
(a) providing the host cell of claim 8 ;
(b) culturing the host cell to express the polypeptide, and
(c) recovering the polypeptide from the host cell culture.
10. The vector of claim 7 , wherein the promoter is selected from the group consisting of the tac promoter, the cell wall protein (CWP) promoter, the phosphoglycerate kinase gene promoter, the alcohol dehydrogenase gene promoter, the glyceraldehyde phosphate dehydrogenase promoter, the glycerol kinase P1 gene promoter, the erythromycin resistance gene EP1 promoter and the phage T7 promoter.
11. The recombinant host cell of claim 8 wherein the host cell is a bacterial cell.
12. The host cell according to claim 8 , wherein said cell is selected from the group consisting of Bacillus, Esoherichia, Saccharomyces , and Streptomyces.
13. The host cell according to claim 8 , wherein said cell is a fungal cell selected from the group consisting of a yeast cell and a filamentous fungal cell.
14. The host cell according to claim 8 , wherein said cell is selected from the group consisting of Aspergillus, Fusarium , and Trichoderma.
15. An isolated nucleic acid molecule comprising a nucleotide sequence encoding a polypeptide comprising the amino acid sequence of SEQ ID NO:2 with two or more amino acid residue changes selected from the group consisting of V186T, L283P, and F187S, and further comprising amino acid substitutions at one or more non-essential amino acid residues such that the polypeptide comprises an amino acid sequence that is at least 98% identical to the amino acid sequence SEQ ID NO:2, that has glucose isomerase activity at temperatures between 60° C. and 80° C. under acidic conditions at pH 6 or less, and that has a half life of about 6.4 hours at 80° C. (pH 7.0).
16. An isolated nucleic acid molecule, which comprises a nucleotide sequence coding for a fusion protein comprising a first polypeptide with glucose isomerase activity having the amino acid sequence of SEQ ID NO:2 with two or more amino acid residue changes selected from the group consisting of V186T, L283P and F187S, operably linked to a second polypeptide.