The present invention relates to enzymes and processes. In particular, there is described an isolated polypeptide comprising the amino acid sequence corresponding to Citrobacter freundii phytase or a homologue, a modified form, a functional equivalent or an effective fragment thereof. There is also described a host cell transformed or transfected with a nucleic acid encoding a bacterial phytase enzyme or a modified form as well as the use of such a phytase or modified form in food or animal feed.
1. An isolated polypeptide comprising an amino acid sequence corresponding to Citrobacter freundii phytase, wherein the polypeptide has phytase activity and wherein the polypeptide comprises the amino acid sequence as shown in SEQ ID NO: 3 or a sequence having at least 90% identity thereto and wherein said polypeptide comprises the mutation R288M according to the numbering in SEQ ID NO:3.
2. An isolated phytase isolated from Citrobacter freundii strain P3-42, deposited under accession number NCIMB 41247.
3. The isolated polypeptide according to claim 1 , having specific activity of at least 1100 U/mg, wherein said specific activity is determined by incubating said phytase in a solution containing 2 mM phytate, 0.8 mM CaCl 2 in 200 mM sodium acetate buffer at pH 3.5.
4. The isolated polypeptide according to claim 1 , having two activity maxima around pH 3 and pH 4-4.5, wherein said activity is determined by incubating said phytase in a solution containing 2 mM phytate, 0.8 mM CaCl 2 in 200 mM sodium acetate buffer.
5. The isolated polypeptide according to claim 1 , further comprising one or more of the following mutations selected from the group consisting of: P229S; D112V; Q82R; Q274H; D112Y; F88Y; K46E; S233C; I384L; Q385R; Q274L; E307Y; T199I; Q82K and T203I.
6. The isolated polypeptide according to claim 1 , comprising a combination of mutations selected from the group consisting of: K46E/Q82H; Q82K/V105I; N148D/T362I; K46E/L414I; F88Y/Y136N; T154I/P386Q; N95P/N96S; N95P/N96P; Q97T/T98G; D224H/N225E; Y177F/T199I; Q274L/Q370H; K46E/N96Y; N148D/L301S; E24D/R288M; E140V/A322V; K46E/S195T; E75K/N365D; T98P/S235A; L160F/L215F; Q274L/K395T; G67R/Q279E/N208T; K161N/P229S/R288M; D53N/D57Y/M152V; F122Y/S156T/P229S; T199I/S206R/T207S; E23K/K46E/Q82H; K46E/Q82H/Q385R; T203W/E204N/K205R; T203W/E204H/K205R; T203W/E204R/K205R; T203W/E204A/K205R; A22T/K151G/N308D; E23K/E75K/F88Y; M152K/N225D/L301S; S78T/Q274L/S408I; L176Q/T199I/T366S; K46E/N77I/T203S; K46R/T199I/D367N; G74R/E204G/R288M; A22T/T199I/S206T/T207A; Q82R/F88Y/L126I/I384L; K46E/Q82H/E168D/Q274L; Q82K/T154I/Q279E/N308T; Q82R/D112V/Q274H/T362A; E24D/E79V/N95D/K360N; E23K/M28L/A109T/T143P/I384L; D53N/D57Y/T199I/P299S/R288M; K46E/Q82H/N148D/T154I/T362I; D53N/D57Y/P229S/R288M/K358R; D53N/D57Y/T154I/P229S/R288M; Y136N/T199I/T203L/E204I/K205P; E23Q/S101F/Q274L/I384M/K391N; K46E/Q82H/N95D/D112V/K142R/D383V; D53N/D57Y/M152V/P229S/R288M/A393P; D53K/D57Y/M152V/P229S/R288M/A393P; D53N/D57Y/F88Y/M152V/P299S/Q279E/N308T; D53N/D57Y/M152V/E204V/P229S/R288M/A393P; D53N/D57Y/M152V/T154I/P229S/R288M/A393P; D53N/D57Y/Q82H/G103E/M152V/P229S/R288M/A393P; K46E/D53N/D57Y/T143I/M152V/L176V/P229S/R288M/A393P; Q82K/F88Y/N96P/Q97T/T98G/V105I/Q274H/Q279E/A393P; Q82R/F88Y/N95P/N96P/Q97T/Q279E/I384L/P386Q/A393P; H18Q/D53N/D57Y/E75V/M152V/A170T/P229S/R288M/Q385R/A393P; Q82K/F88Y/N96P/T98G/Y136N/M152V/Y177F/T362I/I384F/A393P/D397N; D53N/D57Y/F88Y/N95P/N96P/V 105I/D112V/Y136N/N148D/N164D/Q274H/T362I/I384L/A393P; D53N/D57Y/Q82K/F88Y/N95P/P102L/V 105I/Y136N/N148D/Y177F/Q274H/Q279E/T362I/A393P; D53N/D57Y/Q82K/F88Y/N96P/T98G/V105I/D112V/Y177F/Q274L/G343A/T362I/I384L/A393P.
7. A food or animal feed composition comprising the polypeptide as claimed in claim 1 .
8. A method for production of food or animal feed comprising a step of spraying the polypeptide as claimed in claim 1 in liquid form onto said food or animal feed.
9. A method for production of food or animal feed comprising a step of mixing the polypeptide as claimed in claim 1 as a dry product with said food or animal feed.
10. The isolated polypeptide of claim 1 wherein said phytase further comprises one or more of the following mutations: A22T, E23K, E23Q, E24D, M28L, K46E, K46R, D53K, D53N, D57Y, G67R, G74R, E75K, E75V, V77I, S78T, E79V, Q82H, Q82K, Q82R, F88Y, N95D, N95P, N96P, N96S, N96Y, Q97T, T98G, T98P, S101F, P102L, G103E, V105I, A109T, D112V, D112Y, F122Y, L126I, Y136N, E140V, K142R, T143L, T143P, N148D, K151G, M152K, M152V, T154I, S156T, L160F, K161N, N164D, E168D, A170T, L176Q, L176V, Y177F, S195T, T199I, T203I, T203L, T203S, T203W, E204A, E204G, E204H, E204I, E204N, E204R, E204V, K205P, K205R, S206R, S206T, T207A, T207S, L215F, D224H, N225D, N225E, P229S, S233C, S235A, Q274H, Q274L, Q279E, L301S, E307Y, N308D, N308T, A322V, G343A, K358R, K360N, T362A, T362I, N365D, T366S, D367N, Q370H, D383V, I384F, I384L, I384M, Q385R, P386Q, K391N, A393P, K395T, D397N, S408I, L414I.