Carbonic anhydrase having increased stability under high temperature conditions
The present invention relates to polynucleotide and polypeptide sequences of novel carbonic anhydrase variants having increased stability under high temperature conditions compared to native carbonic anhydrase.
1. An isolated polynucleotide encoding a modified carbonic anhydrase polypeptide having increased stability under high temperature conditions compared to unmodified native carbonic anhydrase, said modified carbonic anhydrase comprising the amino acid sequence of SEQ ID NO: 1 with at least two amino acid substitutions selected from Gln136His, Leu223Ser and Leu239Pro and at least 95% identity with said SEQ ID NO: 1.
2. The isolated polynucleotide of claim 1 , wherein said modified carbonic anhydrase further comprises an amino acid substitution consisting of Ala65Thr.
3. The isolated polynucleotide of claim 1 , wherein said modified carbonic anhydrase further comprises an amino acid substitution consisting of Phe93Leu.
4. The isolated polynucleotide of claim 1 , wherein said modified carbonic anhydrase further comprises an amino acid substitution consisting of Leu100His.
5. The isolated polynucleotide of claim 1 , further comprising a substitution at position 136 consisting of Gln136Tyr, when the amino acid sequence of SEQ ID NO: 1 comprises substitutions Leu223Ser and Leu239Pro.
6. The isolated polynucleotide of claim 1 , wherein said amino acid substitutions consist of Gln136His, Leu223Ser and Leu239Pro.
7. The isolated polynucleotide of claim 1 , wherein said modified carbonic anhydrase further comprises an amino acid substitution consisting of Lys153Leu.
8. The isolated polynucleotide of claim 1 , wherein said modified carbonic anhydrase further comprises an amino acid substitution consisting of Leu197Met.
9. The isolated polynucleotide of claim 1 , wherein said modified carbonic anhydrase further comprises an amino acid substitution consisting of Ala247Thr.
10. The isolated polynucleotide of claim 1 , wherein the codon allowing the Gln136His substitution is CAT or CAC.
11. The isolated polynucleotide of claim 1 , wherein the codon allowing the Leu223Ser substitution is TCT, TCC, TCA, TCG, AGT or AGC.
12. An expression or cloning vector comprising an isolated polynucleotide as defined in claim 1 .
13. An isolated polynucleotide encoding a modified carbonic anhydrase polypeptide having increased thermal stability compared to unmodified native carbonic anhydrase, said polynucleotide comprising the nucleic acid sequence of SEQ ID NO: 19, and further comprising a codon allowing a Leu239Pro substitution in the encoded polypeptide.
14. The isolated polynucleotide of claim 1 , wherein the codon allowing the Leu239Pro substitution is CCT, CCC, CCA or CCG.