Polypeptide
We disclose a PS4 variant polypeptide derivable from a parent polypeptide, the parent polypeptide having non-maltogenic exoamylase activity, which PS4 variant polypeptide comprises one or more of the following substitutions: G69P, A141P, G223A, A268P, G313P, S399P and G400P, with reference to the position numbering of a Pseudomonas saccharophilia exoamylase sequence shown as SEQ ID NO: 1. Such PS4 variant polypeptides may be used as exo-amylases, particularly as non-maltogenic exoamylases. Combinations of such PS4 variant polypeptides together with Novamyl are disclosed.
1. A PS4 variant polypeptide derivable from a parent polypeptide, the parent polypeptide having non-maltogenic exoamylase activity, which PS4 variant polypeptide comprises a proline substitution at position 141 with reference to the position numbering of a Pseudomonas saccharophilia exoamylase sequence shown as SEQ ID NO: 1, in which the PS4 variant polypeptide has at least 95% homology to SEQ ID NO: 1 and non-maltogenic exoamylase activity and a higher thermostability compared to the parent polypeptide when tested under the same conditions.
2. A PS4 variant polypeptide according to claim 1 , in which the parent polypeptide comprises a glucan 1,4-alpha-maltotetrahydrolase (EC 3.2.1.60).
3. A PS4 variant polypeptide according to claim 2 , in which the parent polypeptide is a non-maltogenic exoamylase of Pseudomonas saccharophilia or Pseudomonas stutzeri.
4. A PS4 variant polypeptide according to claim 3 , in which the parent polypeptide is a non-maltogenic exoamylase from Pseudomonas saccharophilia having a sequence shown as SEQ ID NO: 1.
5. A PS4 variant polypeptide according to claim 1 , in which the thermostability is measured by establishing a half life (t 1/2 ), at 60 degrees C.
6. A PS4 variant polypeptide according to claim 1 , which has a higher pH stability compared to the parent polypeptide when tested under the same conditions, wherein the pH is between pH5 to pH10.5.
7. A PS4 variant polypeptide according to claim 6 , which has 10% or more pH stability compared to the parent polypeptide, wherein the pH is between pH5 to pH10.5.
8. A PS4 variant polypeptide according to claim 1 , which further comprises an alanine substitution G223A.
9. A PS4 variant polypeptide according to claim 1 , which comprises a sequence PSac-A141P (SEQ ID NO: 3.
10. A PS4 variant polypeptide derivable from a parent polypeptide, the parent polypeptide having non-maltogenic exoamylase activity, which PS4 variant polypeptide comprises a proline substitution at position 141, or an alanine substitution at position 223, or both, with reference to the position numbering of a Pseudomonas saccharophilia exoamylase sequence shown as SEQ ID NO: 1, in which the PS4 variant polypeptide has at least 95% homology to SEQ ID NO:1 and non-maltogenic exoamylase activity and a higher thermostability compared to the parent polypeptide when tested under the same conditions.
11. A polypeptide sequence comprising a sequence of a non-maltogenic exoamylase which has been mutated to include a proline substitution at an amino acid position 141 or an alanine substitution at position 223, or both, with reference to a Pseudomonas saccharophilia exoamylase sequence shown as SEQ ID NO: 1.
12. A PS4 variant polypeptide according to claim 5 , in which the half life (t 1/2 ) at 60 degrees C. is increased by 15% or more relative to the parent polypeptide.
13. A PS4 variant polypeptide according to claim 5 , in which the half life (t 1/2 ) at 60 degrees C. is increased by 50% or more relative to the parent polypeptide.
14. A PS4 variant polypeptide according to claim 5 , in which the half life (t 1/2 ) at 60 degrees C. is increased by 100% or more relative to the parent polypeptide.
15. A PS4 variant polypeptide according to claim 1 , which has a higher activity compared to the parent polypeptide.
16. A PS4 variant polypeptide according to claim 15 , in which the activity is tested using a waxy maize starch incubation test.
17. A PS4 variant polypeptide according to claim 6 , which has 20% or more pH stability compared to the parent polypeptide.
18. A PS4 variant polypeptide according to claim 6 , which has 50% or more pH stability compared to the parent polypeptide.
19. A PS4 variant polypeptide according to claim 1 , in which the polypeptide is obtainable by altering the sequence of a parent polypeptide having non-maltogenic exoamylase activity, by introducing a proline substitution at position 141 with reference to the position numbering of a Pseudomonas saccharophilia exoamylase sequence shown as SEQ ID NO: 1 such that the polypeptide has a higher thermostability compared to the parent polypeptide when tested under the same conditions.
20. A polypeptide according to claim 19 , which is obtainable by altering the sequence of a nucleic acid which encodes the parent polypeptide.
21. A PS4 variant polypeptide derivable from a parent polypeptide, the parent polypeptide being a non-maltogenic exoamylase from Pseudomonas saccharophilia , the variant having a sequence shown as SEQ ID NO: 1 and non-maltogenic exoamylase activity and comprising a proline substitution at position 141, or a polypeptide which has at least 95% similarity thereto, non-maltogenic exoamylase activity and a proline residue at position 141.
22. A polypeptide obtainable by altering the sequence of a non-maltogenic exoamylase from Pseudomonas saccharophilia having a sequence shown as SEQ ID NO: 1, or a polypeptide which has at least 95% similarity thereto, by introducing a proline substitution at position 141.
23. A polypeptide according to claim 22 , which is obtainable by altering the sequence of a nucleic acid which encodes the non-maltogenic exoamylase from Pseudomonas saccharophilia.
24. A combination of a PS4 variant polypeptide according to any preceding claim, together with Novamyl, or a variant, homologue, or mutants thereof which has alpha amylase activity, or a composition comprising such.