Tumor cells induce an immunosuppressive microen-vironment which leads towards tumor immune escape. Understanding the intricacy of immunomodulation by tumor cells is essential for immunotherapy. Indoleamine 2,3-dioxyge...Tumor cells induce an immunosuppressive microen-vironment which leads towards tumor immune escape. Understanding the intricacy of immunomodulation by tumor cells is essential for immunotherapy. Indoleamine 2,3-dioxygenase(IDO) is an immunosuppressive enzyme which mediates tumor immune escape in various cancers including hepatocellular carcinoma(HCC). IDO up-regulation in HCC may lead to recruitment of regulatory T-cells into tumor microenvironment and therefore inhibit local immune responses and promote metastasis. HCC associated fibroblasts stimulate natural killer cells dysfunction through prostaglandin E2 and subsequently IDO promotes favorable condition for tumor metastasis. IDO up-regulation induces immuno-suppression and may enhance the risk of hepatitis C virus and hepatitis B virus induced HCC. Therefore, IDO inhibitors as adjuvant therapeutic agents may have clinical implications in HCC. This review proposes future prospects of IDO not only as a therapeutic target but also as a prognostic marker for HCC.展开更多
AIM: To explore the effect of indoleamine 2,3-dioxygenase(IDO) on recruitment and chemotaxis function of neutrophils in Aspergillus fumigatus(A.fumigatus) keratitis.METHODS: C57BL/6 mice models of A.fumigatus keratiti...AIM: To explore the effect of indoleamine 2,3-dioxygenase(IDO) on recruitment and chemotaxis function of neutrophils in Aspergillus fumigatus(A.fumigatus) keratitis.METHODS: C57BL/6 mice models of A.fumigatus keratitis were established by inoculating hyphae of A.fumigatus evenly on the corneas.The clinical scores and inflammatory cytokines expression were measured respectively on the 1^(st), 3^(th), 5^(th) day after infection.The 1-MT(1 mg/m L) was administered by gavage to exert an inhibitory effect on IDO during infection.The mice were divided into control group, 1-MT group, A.fumigatus(A.F.) group, and 1-MT+A.F.groups.The corneas were monitored by slit lamp microscopy, and recorded disease scores in 3 d after infection.Myeloperoxidase(MPO) assay was done to evaluate the neutrophils infiltration.Immunofluorescence staining was used to detect the recruitment of neutrophils in murine corneas.The m RNA of inflammatory cytokines was measured with reverse transcription-polymerase chain reaction(RT-PCR).RESULTS: The corneal inflammation and the clinical score reached the peak on the 3;day after the corneal infection.The m RNA of inflammatory cytokines of the A.F.group reached the highest on the 3;day after the infection accordingly.Meanwhile, the results of slit light photography indicated that inhibitors of IDO made inflammation more serious contrasted with the A.F.group on the 3;day.Besides, imunofluorescence staining and MPO indicated that 1-MT enhanced the recruitment, infiltration and chemotaxis of neutrophils obviously in contrast to the A.F.group.RT-PCR indicated that 1-MT increased the expression of CXCL-1, ICAM-1, IL-1β, and IL-8 significantly.CONCLUSION: IDO participates in the pathogenesis of A.fumigatus keratitis and plays an important role in inducing immune protection by inhibiting neutrophils-related inflammatory reaction and suppressing recruitment and chemotaxis of the neutrophils.展开更多
BACKGROUND Forkhead box P3(FOXP3)is a specific marker for immunosuppressive regulatory T(T-reg)cells.T-regs and an immunosuppressive enzyme,indoleamine 2,3-dioxygenase(IDO),are associated with advanced disease in canc...BACKGROUND Forkhead box P3(FOXP3)is a specific marker for immunosuppressive regulatory T(T-reg)cells.T-regs and an immunosuppressive enzyme,indoleamine 2,3-dioxygenase(IDO),are associated with advanced disease in cancer.AIM To evaluate the co-expression of FOXP3 and IDO in triple negative breast cancer(TNBC)with respect to hormone-positive breast cancer patients from Pakistan.METHODS Immunohistochemistry was performed to analyze the expression of FOXP3,IDO,estrogen receptor,progesterone receptor,and human epidermal growth factor receptor on tissues of breast cancer patients(n=100):Hormone-positive breast cancer(n=51)and TNBC(n=49).A total of 100 patients were characterized as FOXP3 negative vs positive and further categorized based on low,medium,and high IDO expression score.Univariate and multivariate logistic regression models were used.RESULTS Out of 100 breast tumors,25%expressed FOXP3 positive T-regs.A significant coexpression of FOXP3 and IDO was observed among patients with TNBC(P=0.01)compared to those with hormone-positive breast cancer.Two variables were identified as significant independent risk factors for FOXP3 positive:IDO expression high(adjusted odds ratio(AOR)5.90;95%confidence interval(CI):1.22-28.64;P=0.03)and TNBC(AOR 2.80;95%CI:0.96-7.95;P=0.05).CONCLUSION Our data showed that FOXP3 positive cells might be associated with high expression of IDO in TNBC patients.FOXP3 and IDO co-expression may also suggest its involvement in disease,and evaluation of FOXP3 and IDO expression in TNBC patients may offer a new therapeutic option.展开更多
Dexamethasone (Dex), a ligand for transcriptional enhancement of tyrosine aminotransferase (TAT) and tryptophan 2,3-dioxygenase (TO) genes, (100 nM) maximally increased these mRNA levels at 12 h and 7 h in primary cul...Dexamethasone (Dex), a ligand for transcriptional enhancement of tyrosine aminotransferase (TAT) and tryptophan 2,3-dioxygenase (TO) genes, (100 nM) maximally increased these mRNA levels at 12 h and 7 h in primary cultured rat hepatocytes and the nuclear fraction, respectively. Lactacystin (5 μM) and epoxomicin (0.5 μM), 26S proteasome inhibitors, significantly suppressed the Dex-dependent maximum increase of TAT and TO mRNA levels in the cells and the nuclear fraction. Electrophoretic mobility shift assay demonstrated that lactacystin did not affect binding of glucocorticoid receptor to glucocorticoid responsive element. Furthermore, lactacystin did not affect the activation of GRE luciferase reporter by Dex transfected to the cells. The results demonstrate that 26S proteasome is positively involved in the Dex-dependent increase of TAT and TO mRNA levels in the cells and suggest that the mechanism of action of 26S proteasome may be degradation of some RNase(s), which breaks down TAT and TO mRNAs.展开更多
Background: Indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan (Trp)catabolism have been demonstrated to play an important role in tumor immunosuppression. This study examined the expression and catalytic activity of...Background: Indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan (Trp)catabolism have been demonstrated to play an important role in tumor immunosuppression. This study examined the expression and catalytic activity of IDO1 in penilesquamous cell carcinoma (PSCC) and explored their clinical significance.Methods: IDO1 expression level, serum concentrations of Trp and kynurenine (Kyn)were examined in 114 PSCC patients by immunohistonchemistry and solid-phaseextraction-liquid chromatography-tandem mass spectrometry. The survival was analyzed using Kaplan-Meier method and the log-rank test. Hazard ratio of death was analyzed via univariate and multivariate Cox regression. Immune cell types were definedby principal component analysis. The correlativity was assessed by Pearson’s correlation analysis.Results: The expression level of IDO1 in PSCC cells was positively correlatedwith serum Kyn concentration and Kyn/Trp radio (KTR;both P < 0.001) but negatively correlated with serum Trp concentration (P = 0.001). Additionally, IDO1 upregulation in cancer cells and the increase of serum KTR were significantly associated with advanced N stage (both P < 0.001) and high pathologic grade (P = 0.008and 0.032, respectively). High expression level of IDO1 in cancer cells and serumKTR were associated with short disease-specific survival (both P < 0.001). However, besides N stage (hazard radio [HR], 6.926;95% confidence interval [CI],2.458-19.068;P < 0.001) and pathologic grade (HR, 2.194;95% CI, 1.021-4.529;P = 0.038), only serum KTR (HR, 2.780;95% CI, 1.066-7.215;P = 0.036) was anindependent predictor for PSCC prognosis. IDO1 expression was positively correlated with the expression of interferon-𝛾 (IFN𝛾, P < 0.001) and immunosuppressivemarkers (programmed cell death protein 1, cytotoxic T-lymphocyte-associated protein 4 and programmed death-ligand 1 and 2;all P < 0.05), and the infiltration ofimmune cells (including cytotoxic T lymphocytes, regulatory T lymphocytes, tumorassociated macrophages, and myeloid-derived suppressor cells;all P < 0.001) inPSCC tissues. Furthermore, the expression of IDO1 was induced by IFN𝛾 in a dosedependent manner in PSCC cells.Conclusions: IFN𝛾-induced IDO1 plays a crucial role in immunoediting andimmunosuppression in PSCC. Additionally, serum KTR, an indicator of IDO1catabolic activity, can be utilized as an independent prognostic factor for PSCC.展开更多
Background Increasing evidence suggests that, by the production of indoleamine 2, 3-dioxygenase （IDO）, dendritic cells （DC） may reduce the activity of T lymphocytes and inhibit T lymphocyte proliferation-induced i...Background Increasing evidence suggests that, by the production of indoleamine 2, 3-dioxygenase （IDO）, dendritic cells （DC） may reduce the activity of T lymphocytes and inhibit T lymphocyte proliferation-induced immune tolerance.One promising way is inspired by increasing IDO expression in DG cells for immune tolerance after transplantation. The aim of this work was to examine the effect of interferon-y （IFN-γ） on the expression of IDO by DC.Methods Spleen-derived rat DCs were cultured and induced by cytokines, and the expression of OX62 and surface molecules CD80 and CD86 were measured with flow cytometry. After the DCs were induced by IFN-γ at different concentrations （0, 100, 300, 500 U/ml）, the expression levels of IDO mRNA were measured with real-time PCR, and the expression levels of IDO protein in DCs were measured with Western blotting. The allogeneic mixed lymphocyte reaction （MLR） was used to test the effects of DCs incubated with different concentrations of IFN-γ on allogeneic T lymphocyte proliferation.Results Under the microscope, the DCs induced by IFN-γ showed a typical dendritic morphology. The expression rate of OX62 was above 80% and the positive expression rates of CD80 and CD86 were both about 80%. The expressions of IDO mRNA and IDO protein increased gradually with the increase of IFN-γ concentration, showing statistical significance in the differences between the groups （P 〈0.05）. Compared with the control DC, the DC incubated with IFN-γ had a notable decrease in allostimulatory activity （P 〈0.05）. With the increasing IFN-γ concentration, the T lymphocyte proliferation decreased, and the difference between the groups was also statistically significant （P 〈0.05）.Conclusions The highly purified spleen derived rat DCs can be successfully acquired through the improved adhesion in-vitro method. IFN-γ can induce increased expression of IDO in spleen-derived rat DCs and reduce the spleen DCs＇ capacity to stimulate the proliferation of allogeneic T cells.展开更多
A mulfistep conversion system composed of phenol hydroxylase （PHrND） and 2,3-dihydroxy-biphenyl 1,2-dioxygenase （BphCLA_4） was used to synthesize methylcatechols and semialdehydes from o- and m-cresol for the firs...A mulfistep conversion system composed of phenol hydroxylase （PHrND） and 2,3-dihydroxy-biphenyl 1,2-dioxygenase （BphCLA_4） was used to synthesize methylcatechols and semialdehydes from o- and m-cresol for the first time. Docking studies displayed by PyMOL predicted that cresols and methylcatechols could be theoretically transformed by this multistep conversion system~ High performance liquid chromatography mass spectrometry （HPLC-MS） analysis also indicated that the products formed from multistep conversion were the corresponding 3-methylcatechol, 4-methylcatechol, 2- hydroxy-3-methyl-6-oxohexa-2,4-dienoic acid （2- hydroxy-3-methyl-ODA） and 2-hydroxy-5-methyl-6-oxo- hexa-2,4-dienoic acid （2-hydroxy-5-methyl-ODA）. The optimal cell concentrations of the recombinant E. coli strain BL21 （DE3） expressing phenol hydroxylase （PHrND） and 2,3-dihydroxy-biphenyl 1,2-dioxygenase （BphCLA_4） and pH for the multistep conversion of o- and m-cresol were 4.0 （g-L-1 cell dry weight） and pH 8.0, respectively. For the first step conversion, the formation rate of 3- methylcatechol （0.29μmol·L-1·min-1·mg-1cell dry weight） from o-cresol was similarly with that ofmethylca- techols （0.28 μmol·L-1·min-1·mg-1 cell dry weight） from m-cresol by strain PHrND. For the second step conversion, strain BphCLA_4 showed higher formation rate （0.83 μmol·L-1·min-1·mg-1 cell dry weight） for 2-hydroxy-3-methyl- ODA and 2-hydroxy-5-methyl-ODA from m-cresol, which was 1.1-fold higher than that for 2-hydroxy-3-methyl- ODA （0.77 μmol·L-1·min-1·mg-1. mglcell dry weight） from ocresol. The present study suggested the potential application of the multistep conversion system for the production of chemical synthons and high-value products.展开更多
The selenomethionyl derivative of the thermo-stable catechol 2,3-dioxygenase (SeMet-TC23O) is expressed, purified and crystallized. By using multiwave length anoma-lous dispersion (MAD) phasing techniques, the crystal...The selenomethionyl derivative of the thermo-stable catechol 2,3-dioxygenase (SeMet-TC23O) is expressed, purified and crystallized. By using multiwave length anoma-lous dispersion (MAD) phasing techniques, the crystal structure of TC23O at 0.3 nm resolutions is determined. TC23O is a homotetramer. Each monomer is composed of N-terminal and C-terminal domains (residues 1-153 and 153-319, respectively). The two domains are proximately symmetric by a non-crystallographic axis. Each domain contains two characteristic motifs which are found in almost all of extradial dioxygenases.展开更多
文摘Tumor cells induce an immunosuppressive microen-vironment which leads towards tumor immune escape. Understanding the intricacy of immunomodulation by tumor cells is essential for immunotherapy. Indoleamine 2,3-dioxygenase(IDO) is an immunosuppressive enzyme which mediates tumor immune escape in various cancers including hepatocellular carcinoma(HCC). IDO up-regulation in HCC may lead to recruitment of regulatory T-cells into tumor microenvironment and therefore inhibit local immune responses and promote metastasis. HCC associated fibroblasts stimulate natural killer cells dysfunction through prostaglandin E2 and subsequently IDO promotes favorable condition for tumor metastasis. IDO up-regulation induces immuno-suppression and may enhance the risk of hepatitis C virus and hepatitis B virus induced HCC. Therefore, IDO inhibitors as adjuvant therapeutic agents may have clinical implications in HCC. This review proposes future prospects of IDO not only as a therapeutic target but also as a prognostic marker for HCC.
基金Supported by the National Natural Science Foundation of China (No.81870632)the Youth National Natural Science Foundation of China (No.81700800)the Natural Science Foundation of Shandong Province (No.ZR2017MH008)。
文摘AIM: To explore the effect of indoleamine 2,3-dioxygenase(IDO) on recruitment and chemotaxis function of neutrophils in Aspergillus fumigatus(A.fumigatus) keratitis.METHODS: C57BL/6 mice models of A.fumigatus keratitis were established by inoculating hyphae of A.fumigatus evenly on the corneas.The clinical scores and inflammatory cytokines expression were measured respectively on the 1^(st), 3^(th), 5^(th) day after infection.The 1-MT(1 mg/m L) was administered by gavage to exert an inhibitory effect on IDO during infection.The mice were divided into control group, 1-MT group, A.fumigatus(A.F.) group, and 1-MT+A.F.groups.The corneas were monitored by slit lamp microscopy, and recorded disease scores in 3 d after infection.Myeloperoxidase(MPO) assay was done to evaluate the neutrophils infiltration.Immunofluorescence staining was used to detect the recruitment of neutrophils in murine corneas.The m RNA of inflammatory cytokines was measured with reverse transcription-polymerase chain reaction(RT-PCR).RESULTS: The corneal inflammation and the clinical score reached the peak on the 3;day after the corneal infection.The m RNA of inflammatory cytokines of the A.F.group reached the highest on the 3;day after the infection accordingly.Meanwhile, the results of slit light photography indicated that inhibitors of IDO made inflammation more serious contrasted with the A.F.group on the 3;day.Besides, imunofluorescence staining and MPO indicated that 1-MT enhanced the recruitment, infiltration and chemotaxis of neutrophils obviously in contrast to the A.F.group.RT-PCR indicated that 1-MT increased the expression of CXCL-1, ICAM-1, IL-1β, and IL-8 significantly.CONCLUSION: IDO participates in the pathogenesis of A.fumigatus keratitis and plays an important role in inducing immune protection by inhibiting neutrophils-related inflammatory reaction and suppressing recruitment and chemotaxis of the neutrophils.
文摘BACKGROUND Forkhead box P3(FOXP3)is a specific marker for immunosuppressive regulatory T(T-reg)cells.T-regs and an immunosuppressive enzyme,indoleamine 2,3-dioxygenase(IDO),are associated with advanced disease in cancer.AIM To evaluate the co-expression of FOXP3 and IDO in triple negative breast cancer(TNBC)with respect to hormone-positive breast cancer patients from Pakistan.METHODS Immunohistochemistry was performed to analyze the expression of FOXP3,IDO,estrogen receptor,progesterone receptor,and human epidermal growth factor receptor on tissues of breast cancer patients(n=100):Hormone-positive breast cancer(n=51)and TNBC(n=49).A total of 100 patients were characterized as FOXP3 negative vs positive and further categorized based on low,medium,and high IDO expression score.Univariate and multivariate logistic regression models were used.RESULTS Out of 100 breast tumors,25%expressed FOXP3 positive T-regs.A significant coexpression of FOXP3 and IDO was observed among patients with TNBC(P=0.01)compared to those with hormone-positive breast cancer.Two variables were identified as significant independent risk factors for FOXP3 positive:IDO expression high(adjusted odds ratio(AOR)5.90;95%confidence interval(CI):1.22-28.64;P=0.03)and TNBC(AOR 2.80;95%CI:0.96-7.95;P=0.05).CONCLUSION Our data showed that FOXP3 positive cells might be associated with high expression of IDO in TNBC patients.FOXP3 and IDO co-expression may also suggest its involvement in disease,and evaluation of FOXP3 and IDO expression in TNBC patients may offer a new therapeutic option.
文摘Dexamethasone (Dex), a ligand for transcriptional enhancement of tyrosine aminotransferase (TAT) and tryptophan 2,3-dioxygenase (TO) genes, (100 nM) maximally increased these mRNA levels at 12 h and 7 h in primary cultured rat hepatocytes and the nuclear fraction, respectively. Lactacystin (5 μM) and epoxomicin (0.5 μM), 26S proteasome inhibitors, significantly suppressed the Dex-dependent maximum increase of TAT and TO mRNA levels in the cells and the nuclear fraction. Electrophoretic mobility shift assay demonstrated that lactacystin did not affect binding of glucocorticoid receptor to glucocorticoid responsive element. Furthermore, lactacystin did not affect the activation of GRE luciferase reporter by Dex transfected to the cells. The results demonstrate that 26S proteasome is positively involved in the Dex-dependent increase of TAT and TO mRNA levels in the cells and suggest that the mechanism of action of 26S proteasome may be degradation of some RNase(s), which breaks down TAT and TO mRNAs.
基金National Natural Science Foundation of China,Grant/Award Number:81772755
文摘Background: Indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan (Trp)catabolism have been demonstrated to play an important role in tumor immunosuppression. This study examined the expression and catalytic activity of IDO1 in penilesquamous cell carcinoma (PSCC) and explored their clinical significance.Methods: IDO1 expression level, serum concentrations of Trp and kynurenine (Kyn)were examined in 114 PSCC patients by immunohistonchemistry and solid-phaseextraction-liquid chromatography-tandem mass spectrometry. The survival was analyzed using Kaplan-Meier method and the log-rank test. Hazard ratio of death was analyzed via univariate and multivariate Cox regression. Immune cell types were definedby principal component analysis. The correlativity was assessed by Pearson’s correlation analysis.Results: The expression level of IDO1 in PSCC cells was positively correlatedwith serum Kyn concentration and Kyn/Trp radio (KTR;both P < 0.001) but negatively correlated with serum Trp concentration (P = 0.001). Additionally, IDO1 upregulation in cancer cells and the increase of serum KTR were significantly associated with advanced N stage (both P < 0.001) and high pathologic grade (P = 0.008and 0.032, respectively). High expression level of IDO1 in cancer cells and serumKTR were associated with short disease-specific survival (both P < 0.001). However, besides N stage (hazard radio [HR], 6.926;95% confidence interval [CI],2.458-19.068;P < 0.001) and pathologic grade (HR, 2.194;95% CI, 1.021-4.529;P = 0.038), only serum KTR (HR, 2.780;95% CI, 1.066-7.215;P = 0.036) was anindependent predictor for PSCC prognosis. IDO1 expression was positively correlated with the expression of interferon-𝛾 (IFN𝛾, P < 0.001) and immunosuppressivemarkers (programmed cell death protein 1, cytotoxic T-lymphocyte-associated protein 4 and programmed death-ligand 1 and 2;all P < 0.05), and the infiltration ofimmune cells (including cytotoxic T lymphocytes, regulatory T lymphocytes, tumorassociated macrophages, and myeloid-derived suppressor cells;all P < 0.001) inPSCC tissues. Furthermore, the expression of IDO1 was induced by IFN𝛾 in a dosedependent manner in PSCC cells.Conclusions: IFN𝛾-induced IDO1 plays a crucial role in immunoediting andimmunosuppression in PSCC. Additionally, serum KTR, an indicator of IDO1catabolic activity, can be utilized as an independent prognostic factor for PSCC.
基金This work was supported by grants from the Shanxi Provincial Natural Science Foundation （No. 2009011052-2） and Scientific Research Foundation for Returned Scholars of the Ministry of Education of China （No. 99）.
文摘Background Increasing evidence suggests that, by the production of indoleamine 2, 3-dioxygenase （IDO）, dendritic cells （DC） may reduce the activity of T lymphocytes and inhibit T lymphocyte proliferation-induced immune tolerance.One promising way is inspired by increasing IDO expression in DG cells for immune tolerance after transplantation. The aim of this work was to examine the effect of interferon-y （IFN-γ） on the expression of IDO by DC.Methods Spleen-derived rat DCs were cultured and induced by cytokines, and the expression of OX62 and surface molecules CD80 and CD86 were measured with flow cytometry. After the DCs were induced by IFN-γ at different concentrations （0, 100, 300, 500 U/ml）, the expression levels of IDO mRNA were measured with real-time PCR, and the expression levels of IDO protein in DCs were measured with Western blotting. The allogeneic mixed lymphocyte reaction （MLR） was used to test the effects of DCs incubated with different concentrations of IFN-γ on allogeneic T lymphocyte proliferation.Results Under the microscope, the DCs induced by IFN-γ showed a typical dendritic morphology. The expression rate of OX62 was above 80% and the positive expression rates of CD80 and CD86 were both about 80%. The expressions of IDO mRNA and IDO protein increased gradually with the increase of IFN-γ concentration, showing statistical significance in the differences between the groups （P 〈0.05）. Compared with the control DC, the DC incubated with IFN-γ had a notable decrease in allostimulatory activity （P 〈0.05）. With the increasing IFN-γ concentration, the T lymphocyte proliferation decreased, and the difference between the groups was also statistically significant （P 〈0.05）.Conclusions The highly purified spleen derived rat DCs can be successfully acquired through the improved adhesion in-vitro method. IFN-γ can induce increased expression of IDO in spleen-derived rat DCs and reduce the spleen DCs＇ capacity to stimulate the proliferation of allogeneic T cells.
基金The authors gratefully acknowledge the financial supports from the National Natural Science Foundation of China （Grant Nos. 51078054, 51108120, and 51178139） and the National Creative Research Group from the National Natural Science Foundation of China （No. 51121062）.
文摘A mulfistep conversion system composed of phenol hydroxylase （PHrND） and 2,3-dihydroxy-biphenyl 1,2-dioxygenase （BphCLA_4） was used to synthesize methylcatechols and semialdehydes from o- and m-cresol for the first time. Docking studies displayed by PyMOL predicted that cresols and methylcatechols could be theoretically transformed by this multistep conversion system~ High performance liquid chromatography mass spectrometry （HPLC-MS） analysis also indicated that the products formed from multistep conversion were the corresponding 3-methylcatechol, 4-methylcatechol, 2- hydroxy-3-methyl-6-oxohexa-2,4-dienoic acid （2- hydroxy-3-methyl-ODA） and 2-hydroxy-5-methyl-6-oxo- hexa-2,4-dienoic acid （2-hydroxy-5-methyl-ODA）. The optimal cell concentrations of the recombinant E. coli strain BL21 （DE3） expressing phenol hydroxylase （PHrND） and 2,3-dihydroxy-biphenyl 1,2-dioxygenase （BphCLA_4） and pH for the multistep conversion of o- and m-cresol were 4.0 （g-L-1 cell dry weight） and pH 8.0, respectively. For the first step conversion, the formation rate of 3- methylcatechol （0.29μmol·L-1·min-1·mg-1cell dry weight） from o-cresol was similarly with that ofmethylca- techols （0.28 μmol·L-1·min-1·mg-1 cell dry weight） from m-cresol by strain PHrND. For the second step conversion, strain BphCLA_4 showed higher formation rate （0.83 μmol·L-1·min-1·mg-1 cell dry weight） for 2-hydroxy-3-methyl- ODA and 2-hydroxy-5-methyl-ODA from m-cresol, which was 1.1-fold higher than that for 2-hydroxy-3-methyl- ODA （0.77 μmol·L-1·min-1·mg-1. mglcell dry weight） from ocresol. The present study suggested the potential application of the multistep conversion system for the production of chemical synthons and high-value products.
基金This workwas supported by the National Natural Science Foundation of China (Grant No. 30070161) the Hundreds Talents Program of the ChineseAcademy of Sciences.
文摘The selenomethionyl derivative of the thermo-stable catechol 2,3-dioxygenase (SeMet-TC23O) is expressed, purified and crystallized. By using multiwave length anoma-lous dispersion (MAD) phasing techniques, the crystal structure of TC23O at 0.3 nm resolutions is determined. TC23O is a homotetramer. Each monomer is composed of N-terminal and C-terminal domains (residues 1-153 and 153-319, respectively). The two domains are proximately symmetric by a non-crystallographic axis. Each domain contains two characteristic motifs which are found in almost all of extradial dioxygenases.
