NOVEL PSICOSE-6-PHOSPHATE PHOSPHATASE, COMPOSITION FOR PRODUCING PSICOSE INCLUDING SAID ENZYME, METHOD FOR PRODUCING PSICOSE USING SAID ENZYME

Abstract

The present application relates to a psicose-6-phosphate phosphatase comprising motif A and motif B, a composition for producing D-psicose comprising the enzyme, and a method for producing D-psicose using the enzyme.

Claims

1. A psicose-6-phosphate phosphatase comprising motif A represented by Xa1-Xa2-Xa3-DPLDG-Xa4 wherein Xa1 is W, F, V, I or A, Xa2 is I, F, V, A or absent, Xa3 is V, I or L, and Xa4 is T or S and motif B represented by Ya1-D-Ya2-Wa1-Ya3-Wa2-Ya4-Wa3 wherein Ya1 is W, Y, T, L or V, Ya2 is V, I, C, F or A, Wa1 is AAG, AAS, SAG, APG, APF, AGG, APL or AGA, Ya3 is W, I, P, M, V, Y, F, R, L, T or S, Wa2 is LLV, LIV, LLI, LII, ILI, FIA, ALV, IIA, VLV, VIL, TIG, NFC or PIF, Ya4 is E, R, S, T, L, K or P, and Wa3 is EAGG, EGGG, EAKG, KAGG, AAGG, YVDG, EAGA or RLGV.

2. The psicose-6-phosphate phosphatase according to claim 1, wherein, in motif A, Xa1 is W or F, Xa2 is I or V, Xa3 is V or I, and Xa4 is T; and in motif B, Ya1 is W, Ya2 is V or I, Wa1 is AAG, Ya3 is W, I or V, Wa2 is LLV, LIV, LII or LLI, Ya4 is E, R or S, and Wa3 is EAGG or EGGG.

3. The psicose-6-phosphate phosphatase according to claim 1, wherein the psicose-6-phosphate phosphatase comprises any one of the amino acid sequences set forth in SEQ ID NOS: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 or a sequence having a identity of at least 85% to an amino acid sequence other than motif A and motif B in the sequences set forth in SEQ ID NOS: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20.

4. The psicose-6-phosphate phosphatase according to claim 3, wherein the psicose-6-phosphate phosphatase consists of the amino acid sequence set forth in SEQ ID NO: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 is encoded by the nucleotide sequence set forth in SEQ ID NO: 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39 or 40, respectively.

5. A nucleic acid encoding the psicose-6-phosphate phosphatase according to claim 1.

6. A transformant comprising the nucleic acid according to claim 5.

7. (canceled)

8. (canceled)

9. (canceled)

10. A method for producing D-psicose comprising contacting the enzyme according to claim 1 or an inositol-mono-phosphatase, a microorganism expressing the enzyme or a culture of the microorganism with D-psicose-6-phosphate to convert the D-psicose-6-phosphate to D-psicose.

11. (canceled)

12. The method according to claim 10, further comprising, prior to the conversion of D-psicose-6-phosphate to D-psicose, contacting a D-fructose-6-phosphate-3-epimerase, a microorganism expressing the D-fructose-6-phosphate-3-epimerase or a culture of the microorganism with D-fructose-6-phosphate to convert the D-fructose-6-phosphate to D-psicose-6-phosphate.

13. The method according to claim 11, further comprising, prior to the conversion of D-fructose-6-phosphate to D-psicose-6-phosphate, contacting a D-glucose-6-phosphate-isomerase, a microorganism expressing the D-glucose-6-phosphate-isomerase or a culture of the microorganism with D-glucose-6-phosphate to convert the D-glucose-6-phosphate to D-fructose-6-phosphate.

14. The method according to claim 13, further comprising, prior to the conversion of D-glucose-6-phosphate to D-fructose-6-phosphate, contacting a phosphoglucomutase, a microorganism expressing the phosphoglucomutase or a culture of the microorganism with D-glucose-1-phosphate to convert the D-glucose-1-phosphate to D-glucose-6-phosphate.

15. The method according to claim 14, further comprising, prior to the conversion of D-glucose-6-phosphate to D-fructose-6-phosphate, contacting a glucokinase, a microorganism expressing the glucokinase or a culture of the microorganism and a phosphate with glucose to convert the glucose to D-glucose-6-phosphate.

16. The method according to claim 15, further comprising, prior to the conversion of D-glucose-1-phosphate to D-glucose-6-phosphate, contacting an α-glucan phosphorylase, a starch phosphorylase, a maltodextrin phosphorylase or a sucrose phosphorylase, a microorganism expressing the phosphorylase or a culture of the microorganism and a phosphate with starch, maltodextrin, sucrose or a combination thereof to convert the starch, maltodextrin, sucrose or combination thereof to D-glucose-1-phosphate.

17. The method according to claim 15, further comprising, prior to the conversion of glucose to D-glucose-6-phosphate, contacting an α-amylase, a pullulanase, a glucoamylase, a sucrase or an isoamylase, a microorganism expressing the α-amylase, pullulanase, glucoamylase, sucrase or isoamylase or a culture of the microorganism with starch, maltodextrin, sucrose or a combination thereof to convert the starch, maltodextrin, sucrose or combination thereof to glucose.

18. A method for producing D-psicose comprising contacting (a) the psicose-6-phosphate phosphatase according to claim 1, a D-fructose-6-phosphate-3-epimerase, a D-glucose-6-phosphate-isomerase, a phosphoglucomutase or a glucokinase and an α-glucan phosphorylase, a starch phosphorylase, a maltodextrin phosphorylase, a sucrose phosphorylase, an α-amylase, a pullulanase, an isoamylase, a glucoamylase or a sucrase or (b) a microorganism expressing the enzymes (a) or a culture of the microorganism with starch, maltodextrin, sucrose or a combination thereof and a phosphate.

19. The method according to claim 10, wherein the contact reaction is carried out at a pH of 5.0 to 9.0, at a temperature of 40° C. to 80° C. and/or for 2 hours to 24 hours.

20. A nucleic acid encoding the psicose-6-phosphate phosphatase according to claim 2.

21. A nucleic acid encoding the psicose-6-phosphate phosphatase according to claim 3.

22. A nucleic acid encoding the psicose-6-phosphate phosphatase according to claim 4.

Description

DESCRIPTION OF DRAWINGS

[0066] FIG. 1 schematically shows the enzymatic reaction pathways for the production of D-psicose from starch (e.g., maltodextrin) or glucose.

[0067] FIGS. 2a, 2b and 2c show SDS-PAGE gel images of size markers (M), expressed coenzymes (S), and purified recombinant enzymes (E) (pET21a-CJ_Rma, pET21a-CJ_Tle, pET21a-CJ_Mrub, pET21a-CJ_Dtu, pBT7-C-His-CJ_Pfe, pBT7-C-His-CJ_Twi, pBT7-C-His-CJ_Tth, pBT7-C-His-CJ_Tli, pBT7-C-His-CJ_Gst, pBT7-C-His-CJ_Ath, pBT7-C-His-CJ_Sac, pBT7-C-His-CJ_Tta, pBT7-C-His-CJ_Pfu, pBT7-C-His-CJ_Afu, pBT7-C-His-CJ_Aac, pET21a-CJ_Msi, pET21a-CJ_Mruf, pET21a-CJ_Mta, pET21a-CJ_Mch, pET21a-CJ_Mce) to determine molecular weights thereof, which were taken after protein electrophoresis.

[0068] FIG. 3a shows the relative activities of inositol-mono-phosphatases (pET21a-CJ_Rma, pET21a-CJ_Tle, pET21a-CJ_Mrub, pET21a-CJ_Dtu, pBT7-C-His-CJ_Pfe, pBT7-C-His-CJ_Twi, pBT7-C-His-CJ_Tth, pBT7-C-His-CJ_Tli, pBT7-C-His-CJ_Gst, pBT7-C-His-CJ_Ath, pBT7-C-His-CJ_Sac, pBT7-C-His-CJ_Tta, pBT7-C-His-CJ_Pfu, pBT7-C-His-CJ_Afu, pBT7-C-His-CJ_Aac) for dephosphorylation (%, left Y axis, histogram) and the selective dephosphorylation rates by the inositol-mono-phosphatases in a dephosphorylation mixture containing D-glucose-6-phosphate, D-glucose-1-phosphate, D-fructose-6-phosphate, and D-psicose-6-phosphate (%, right Y axis, square dots).

[0069] FIG. 3b compares the relative activities (%) of inositol-mono-phosphatases (pET21a-CJ_Mrub, pET21a-CJ_Msi, pET21a-CJ_Mruf, pET21a-CJ_Mta, pET21a-CJ_Mch, pET21a-CJ_Mce) for dephosphorylation.

[0070] FIG. 4a shows HPLC chromatograms confirming the production of D-psicose from maltodextrin through multiple enzymatic reactions with an a-glucan phosphorylase, a phosphoglucomutase, a D-glucose-6-phosphate-isomerase, a 4-a-glucanotransferase, a D-fructose-6-phosphate-3-epimerase, and a psicose-6-phosphate phosphatase.

[0071] FIG. 4b shows HPLC chromatograms confirming the production of D-psicose through selective dephosphorylation of D-psicose-6-phosphate in a reaction solution containing D-glucose-1-phosphate, D-glucose-6-phosphate, D-fructose-6-phosphate, and D-psicose-6-phosphate in the presence of an inositol-mono-phosphatase according to the present application.

MODE FOR INVENTION

[0072] The present application will be explained in detail with reference to the following examples. However, these examples are provided to assist in understanding the present application and do not limit the scope of the present application.

Examples

Example 1: Production of Recombinant Expression Vectors of Inositol-Mono-Phosphatases and Transformed Microorganisms

[0073] To provide psicose-6-phosphate phosphatase necessary for the D-psicose production pathway, thermoresistant inositol-mono-phosphatase genes were screened. Specifically, inositol-mono-phosphatase genes (Rma, Tle, Mrub, Dtu, Msi, Mruf, Mta, Mch, and Mce) were screened from the genomic sequences of Rhodothermus marinus, Thermotoga lettingae, Meiothermus ruber, Dictyoglomus turgidum, Pyrobaculum ferrireducens, Thermoanaerobacter wiegelii, Thermus thermophilus, Thermococcus litoralis, Geobacillus stearothermophilus, Anaerolinea thermophila, Sulfolobus acidocaldarius, Thermosulfdibacter takai, Pyrococcus furiosus, Archaeoglobus fulgidus, Alicyclobacillus acidocaldarius, Meiothermus silvanus, Meiothermus rufus, Meiothermus taiwanensis, Meiothermus chliarophilus, and Meiothermus cerbereus registered in GenBank.

[0074] Based on information on the nucleotide sequences (SEQ ID NOS: 21, 22, 23, 24, 36, 37, 38, 39, and 40 in the order of the genes) and the amino acid sequences (SEQ ID NOS: 1, 2, 3, 4, 16, 17, 18, 19, and 20 in the order of the genes) of the screened genes, forward primers (SEQ ID NOS: 41, 43, 45, 47, 49, 51, 53, 55, and 57) and reverse primers (SEQ ID NOS: 42, 44, 46, 48, 50, 52, 54, 56, and 58) were designed. The genes were amplified from the genomic DNAs of Rhodothermus marinus, Thermotoga lettingae, Meiothermus ruber, Dictyoglomus turgidum, Meiothermus silvanus, Meiothermus rufus, Meiothermus taiwanensis, Meiothermus chliarophilus, and Meiothermus cerbereus by polymerase chain reaction (PCR) using the synthesized primers. The amplified inositol-mono-phosphatase genes were inserted into plasmid vector pET21a (Novagen) for E. coli expression using restriction enzymes NdeI and XhoI or SalI to construct recombinant expression vectors, which were named pET21a-CJ_Rma(Nde I/Xho I), pET21a-CJ_Tle(Nde I/Xho I), pET21a-CJ_Mrub(Nde I/Xho I), pET21a-CJ_Dtu(Nde I/Xho I), pET21a-CJ_Msi(Nde I/Sal I), pET21a-CJ_Mruf(Nde I/Sal I), pET21a-CJ_Mta(Nde I/Sal I), pET21a-CJ_Mch(Nde I/Sal I), and pET21a-CJ_Mce(Nde I/Sal I).

[0075] Additionally, inositol-mono-phosphatase genes (Pfe, Twi, Tth, Tli, Gst, Ath, Sac, Tta, Pfu, Afu, and Aac) derived from Pyrobaculumferrireducens, Thermoanaerobacter wiegelii, Thermus thermophilus, Thermococcus litoralis, Geobacillus stearothermophilus, Anaerolinea thermophila, Sulfolobus acidocaldarius, Thermosulfdibacter takai, Pyrococcus furiosus, Archaeoglobus fulgidus, and Alicyclobacillus acidocaldarius were screened. Based on information on the nucleotide sequences (SEQ ID NOS: 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, and 35 in the order of the genes) and the amino acid sequences (SEQ ID NOS: 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15 in the order of the genes) of the screened genes, DNA synthesis was requested to Bioneer (Korea). The DNAs were inserted into vector pBT7-C-His (Bioneer) to construct recombinant expression vectors, which were named pBT7-C-His-CJ_Pfe, pBT7-C-His-CJ_Twi, pBT7-C-His-CJ_Tth, pBT7-C-His-CJ_Tli, pBT7-C-His-CJ_Gst, pBT7-C-His-CJ_Ath, pBT7-C-His-CJ_Sac, pBT7-C-His-CJ_Tta, pBT7-C-His-CJ_Pfu, pBT7-C-His-CJ_Afu, and pBT7-C-His-CJ_Aac.

[0076] The expression vectors were transformed into strain E. coli BL21(DE3) by a general transformation technique (see Sambrook et al. 1989) to produce transformed microorganisms, which were named E. coli BL21(DE3)/pET21a-CJ_Rma (E. coli_P1_CJ_Rma, KCCM12057P), E. coli BL21(DE3)/pET21a-CJ_Tle (E. coli_P2_CJ_Tle, KCCM12058P), E. coli BL21(DE3)/pET21a-CJ_Mrub (E. coli_P3_CJ_Mrub, KCCM12059P), E. coli BL21(DE3)/pET21a-CJ_Dtu (E. coli_P4_CJ_Dtu, KCCM12060P), E. coli BL21(DE3)/pBT7-C-His-CJ_Pfe (E. coli_P5_CJ_Pfe, KCCM12061P), E. coli BL21(DE3)/pBT7-C-His-CJ_Twi (E. coli_P6_CJ_Twi, KCCM12062P), E. coli BL21(DE3)/pBT7-C-His-CJ_Tth (E. coli_P7_CJ_Tth, KCCM12063P), E. coli BL21(DE3)/pBT7-C-His-CJ_Tli (E. coli_P8_CJ_Tli, KCCM12064P), E. coli BL21(DE3)/pBT7-C-His-CJ_Gst (E. coli_P9_CJ_Gst, KCCM12065P), E. coli BL21(DE3)/pBT7-C-His-CJ_Ath (E. coli_P10_CJ_Ath, KCCM12066P), E. coli BL21(DE3)/pBT7-C-His-CJ_Sac (E. coli_P11_CJ_Sac, KCCM12067P), E. coli BL21(DE3)/pBT7-C-His-CJ_Tta (E. coli_P12_CJ_Tta, KCCM12068P), E. coli BL21(DE3)/pBT7-C-His-CJ_Pfu (E. coli_P13_CJ_Pfu, KCCM12069P), E. coli BL21(DE3)/pBT7-C-His-CJ_Afu (E. coli_P14_CJ_Afu, KCCM12070P), E. coli BL21(DE3)/pBT7-C-His-CJ_Aac (E. coli_P15_CJ_Aac, KCCM12071P), E. coli BL21(DE3)/pET21a-CJ_Msi (E. coli P16_CJ_Msi, KCCM12072P), E. coli BL21(DE3)/pET21a-CJ_Mruf (E. coli_P17_CJ_Mruf, KCCM12073P), E. coli BL21(DE3)/pET21a-CJ_Mta (E. coli_P18_CJ_Mta, KCCM12074P), E. coli BL21(DE3)/pET21a-CJ_Mch (E. coli_P19_CJ_Mch, KCCM12075P), and E. coli BL21(DE3)/pET21a-CJ_Mce (E. coli_P20_CJ_Mce, KCCM12076P).

[0077] The transformed strains were deposited at the Korean Culture Center of Microorganisms (KCCM) on Jul. 10, 2017 under the Budapest Treaty (Accession Nos.: KCCM12057P to KCCM12076P).

Example 2: Production of Enzymes Necessary for D-Psicose Production Pathway

[0078] To provide an a-glucan phosphorylase, a phosphoglucomutase, a D-glucose-6-phosphate-isomerase, and a D-fructose-6-phosphate-3-epimerase derived from Thermotoga neapolitana as thermoresistant enzymes necessary for the D-psicose production pathway, genes corresponding to the enzymes were screened (ct1, ct2, tn1 and fp3e in the order of the enzymes).

[0079] Based on the nucleotide sequences (SEQ ID NOS: 60, 62, 64, and 66 in the order of the enzymes) and the amino acid sequences (SEQ ID NOS: 59, 61, 63, and 65 in the order of the enzymes) of the screened genes, forward primers (SEQ ID NOS: 69, 71, 73 and 75) and reverse primers (SEQ ID NOS: 70, 72, 74 and 76) were designed. The enzyme genes were amplified from the genomic DNA of Thermotoga neapolitana as a template by polymerase chain reaction (PCR) using the primers. PCR was performed for a total of 25 cycles using the following conditions: denaturization at 95° C. for 30 sec, annealing at 55° C. for 30 sec, and polymerization at 68° C. for 2 min. The amplified enzyme genes were inserted into plasmid vector pET21a (Novagen) for E. coli expression using restriction enzymes NdeI and XhoI to construct recombinant expression vectors, which were named pET21a-CJ_ct1, pET21a-CJ_ct2, pET21a-CJ_tn1, and pET21a-CJ_fp3e. The recombinant expression vectors were transformed into strain E. coli BL21(DE3) by a general transformation technique (see Sambrook et al. 1989) to produce transformed microorganisms, which were named E. coli BL21(DE3)/pET21a-CJ_ct1 (KCCM11990P), E. coli BL21(DE3)/pET21a-CJ_ct2 (KCCM11991P), E. coli BL21(DE3)/pET21a-CJ_tn1 (KCCM11992P), and E. coli BL21(DE3)/CJ_tn_fp3e (KCCM11848P). The strains were deposited at the Korean Culture Center of Microorganisms (KCCM) on Jun. 23, 2016 under the Budapest Treaty.

Example 3: Production of Recombinant Enzymes

[0080] In this example, recombinant enzymes were produced. First, a culture tube containing 5 ml of LB liquid medium was inoculated with each of the transformed microorganisms produced in Examples 1 and 2. The inoculum was cultured in a shaking incubator at 37° C. until an absorbance of 2.0 at 600 nm was reached. The culture broth was added to LB liquid medium in a culture flask, followed by main culture. When the absorbance of the culture at 600 nm reached 2.0, 1 mM IPTG was added to induce the expression and production of a recombinant enzyme. The culture temperature was maintained at 37° C. with stirring at 180 rpm. The culture broth was centrifuged at 8,000×g and 4° C. for 20 min to collect bacterial cells. The collected bacterial cells were washed twice with 50 mM Tris-HCl buffer (pH 8.0) and suspended in the same buffer. Then, cells were disrupted using an ultrasonic homogenizer. The cell lysate was centrifuged at 13,000×g and 4° C. for 20 min. The recombinant enzyme was purified from the supernatant by His-tag affinity chromatography. The purified recombinant enzyme was dialyzed against 50 mM Tris-HCl buffer (pH 8.0) and was then used for subsequent reaction. The molecular weight of the purified recombinant enzyme was determined by SDS-PAGE.

[0081] The names and molecular weights of the purified enzymes produced using the transformed microorganisms are as follows (FIGS. 2a, 2b and 2c):

[0082] 30.3 kDa for the enzyme (RMA) produced from E. coli BL21(DE3))/pET21a-CJ_Rma (E. coli_P1_CJ_Rma);

[0083] 28.5 kDa for the enzyme (TLE) produced from E. coli BL21(DE3)/pET21a-CJ_Tle (E. coli_P2_CJ_Tle);

[0084] 28 kDa for the enzyme (MRUB) produced from E. coli BL21(DE3)/pET21a-CJ_Mrub (E. coli_P3_CJ_Mrub);

[0085] 30.2 kDa for the enzyme (DTU) produced from E. coli BL21(DE3)/pET21a-CJ_Dtu (E. coli_P4_CJ_Dtu);

[0086] kDa for the enzyme (PFE) produced from E. coli BL21(DE3)/pBT7-C-His-CJ_Pfe (E. coli_P5_CJ_Pfe);

[0087] 28.8 kDa for the enzyme (TWI) produced from E. coli BL21(DE3)/pBT7-C-His-CJ_Twi (E. coli_P6_CJ_Twi);

[0088] kDa for the enzyme (TTH) produced from E. coli BL21(DE3)/pBT7-C-His-CJ_Tth (E. coli P7_CJ_Tth);

[0089] 28 kDa for the enzyme (TLI) produced from E. coli BL21(DE3)/pBT7-C-His-CJ_Tli (E. coli_P8_CJ_Tli);

[0090] kDa for the enzyme (GST) produced from E. coli BL21(DE3)/pBT7-C-His-CJ_Gst (E. coli_P9_CJ_Gst);

[0091] 28.7 kDa for the enzyme (ATH) produced from E. coli BL21(DE3)/pBT7-C-His-CJ_Ath (E. coli_P10_CJ_Ath);

[0092] kDa for the enzyme (SAC) produced from E. coli BL21(DE3)/pBT7-C-His-CJ_Sac (E. coli_P11_CJ_Sac);

[0093] 28.6 kDa for the enzyme (TTA) produced from E. coli BL21(DE3)/pBT7-C-His-CJ_Tta (E. coli_P12_CJ_Tta);

[0094] 27.9 kDa for the enzyme (PFU) produced from E. coli BL21(DE3)/pBT7-C-His-CJ_Pfu (E. coli_P13_CJ_Pfu);

[0095] 28 kDa for the enzyme (AFU) produced from E. coli BL21(DE3)/pBT7-C-His-CJ_Afu (E. coli_P14_CJ_Afu);

[0096] 29 kDa for the enzyme (AAC) produced from E. coli BL21(DE3)/pBT7-C-His-CJ_Aac (E. coli_P15_CJ_Aac);

[0097] 28.1 kDa for the enzyme (MSI) produced from E. coli BL21(DE3)/pET21a-CJ_Msi (E. coli_P16_CJ_Msi);

[0098] 28 kDa for the enzyme (MRUF) produced from E. coli BL21(DE3)/pET21a-CJ_Mruf (E. coli_P17_CJ_Mruf);

[0099] 28.1 kDa for the enzyme (MTA) produced from E. coli BL21(DE3))/pET21a-CJ_Mta (E. coli_P18_CJ_Mta);

[0100] 28.4 kDa for the enzyme (MCH) produced from E. coli BL21(DE3))/pET21a-CJ_Mch (E. coli_P19_CJ_Mch);

[0101] 28.1 kDa for the enzyme (MCE) produced from E. coli BL21(DE3))/pET21a-CJ_Mce (E. coli_P20_CJ_Mce);

[0102] The enzyme (CT1) produced from E. coli BL21(DE3)/pET21a-CJ_ct1 (KCCM11990P);

[0103] The enzyme (CT2) produced from E. coli BL21(DE3)/pET21a-CJ_ct2 (KCCM11991P);

[0104] The enzyme (TN1) produced from E. coli BL21(DE3)/pET21a-CJ_tn1 (KCCM11992P); and

[0105] The enzyme (FP3E) produced from E. coli BL21(DE3)/CJ_tn_fp3e (KCCM11848P).

Example 4: Analysis of Activities of the Inositol-Mono-Phosphatases

[0106] 4-1. Analysis of Activities of the Psicose-6-Phosphate Phosphatases

[0107] Psicose-6-phosphate was difficult to purchase. Thus, the inventors directly produced D-psicose-6-phosphate from D-fructose-6-phosphate and investigated the activities of the inositol-mono-phosphatases for D-psicose production.

[0108] Specifically, 50 mM D-fructose-6-phosphate was suspended in 50 mM Tris-HCl (pH 7.0), and then the D-fructose-6-phosphate-3-epimerase (FP3E) produced in Example 3 and 0.1 unit/ml of each of the 20 inositol-mono-phosphatases were added thereto. The mixture was allowed to react at 70° C. for 1 h. The production of D-psicose was confirmed by HPLC (SP_0810 column (Shodex), Aminex HPX-87C column (Bio-RAD), 80° C., mobile phase flow rate 0.6 ml/min, refractive index detector).

[0109] The dephosphorylation potency of the all 20 inositol-mono-phosphatases for D-psicose-6-phosphate were investigated (FIGS. 3a and 3b).

[0110] 4-2. Analysis of Activities of the Inositol-Mono-Phosphatases for Specific Dephosphorylation of D-Psicose-6-Phosphate

[0111] The specific dephosphorylation rates of D-psicose-6-phosphate in a mixture containing D-glucose-6-phosphate, D-glucose-1-phosphate, D-fructose-6-phosphate, and D-psicose-6-phosphate in the presence of the inositol-mono-phosphatases were measured.

[0112] Specifically, 0.1 unit/ml of each of the inositol-mono-phosphatases and 5 mM MgCl.sub.2 were added to a mixture of 1% (w/v) D-glucose-6-phosphate, D-glucose-1-phosphate, D-fructose-6-phosphate, and D-psicose-6-phosphate. The reaction was allowed to proceed at 50° C. for 12 h. The reaction products were analyzed by HPLC (Aminex HPX-87C column (Bio-RAD), 80° C., mobile phase flow rate 0.6 ml/min). A refractive index detector was used to detect the production of D-psicose and other saccharides (fructose and glucose).

[0113] As a result, the enzyme MRUB showed the highest specific dephosphorylation rate of D-psicose-6-phosphate (FIG. 3a).

Example 5: Analysis of Activities of the Enzymes Through Multiple Enzymatic Reactions

[0114] For the production of D-psicose from maltodextrin, the enzymes CT1, CT2, TN1, FP3E and MRUB were allowed to simultaneously react with maltodextrin. 5% (w/v) maltodextrin was added to 0.1 unit/ml of each enzyme, 5 mM MgCl.sub.2, and 20 mM sodium phosphate (pH 7.0). The mixture was allowed to react at a temperature of 50° C. for 12 h. The reaction products were analyzed by HPLC (Aminex HPX-87C column (Bio-RAD), 80° C., mobile phase flow rate 0.6 ml/min), refractive index detector).

[0115] As a result, the production of D-psicose from maltodextrin through the multiple enzymatic reactions was confirmed (FIG. 4a).

[0116] While the embodiment of the present application has been described in detail, it will be understood by those skilled in the art that the application can be implemented in other specific forms without changing the spirit or essential features of the application. Therefore, it should be noted that the forgoing embodiments are merely illustrative in all aspects and are not to be construed as limiting the application. The scope of the application is defined by the appended claims rather than the detailed description of the application. All changes or modifications or their equivalents made within the meanings and scope of the claims should be construed as falling within the scope of the application.