• Microbiology and Biotechnology Letters
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• v.24 no.2
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• pp.222-226
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• 1996

The enzymatic synthesis of 3, 4-dihydroxyphenyl-L-alanine (L-DOPA) was examined for the effects of the reaction additives such as sodium borate, alcohol, and organic solvents. The enzyme used was tyrosine phenol-lyase of Citrobacter freundii KCTC 2006 produced in Escherichia coli. The amounts of tyrosine phenol-lyase and pyridoxal-5-phosphate were optimized to 2.0 units/ml and 0.1 mM, respectively, for the synthetic reaction. Sodium borate, a substance that forms a complex with pyrocatechol, reduced the enzyme deactivation by pyrocatechol although it seriously inhibited the enzyme activity. Among the organic solvents tested, dimethylsulfoxide, dimethylformamide, and alcohol increased the productivity of the L-DOPA synthesis. In a reaction system with 5% methanol, L-DOPA concentration increased up to 210 mM after 24 hours, and 77.1% of which was separated as precipitates. The L-DOPA was purified to 99.96% by solubilizing and recrystallyzing the precipitates.

• Archives of Pharmacal Research
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• v.19 no.4
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• pp.258-260
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• 1996

Palmatine, an protoberberine isoquinoline alkaloid, has been found to inhibit dopamine biosynthesis by reducing tyrosine hydroxylase (TH) activity in PC12 cells (Lee and Kim, 1996). We have therefore investigated the effects of palmatine on bovine adrenal TH. Palmatine showed a mild inhibition on bovine adrenal TH (36.4% inhibition at concentration of $200\muM$). Bovine adrenal TH was inhibited competitively by palmatine with a substrate L-tyrosine. The Ki value was found to be 0.67 mM. This result suggests that the inhibition of TH activity by palmatine may be partially involved in the reduction of dopamine biosynthesis in PC12 cells.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1993.04a
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• pp.117-117
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• 1993

3. 연구결과 출발물질로 L-tyrosine을 사용하여 요오드화, 에스테르화, N-CBZ 및 0-Bn보호기화 및 N-methyl화를 행하여 5단계에 걸쳐 41%의 수율로 N-CBZ-N-methyl-0-Bn-3-iodo-tyrosine을 합성하였다. Ullmann coupling의 반응성 검토를 위해 t-bromophenylala-nine에 반응시킬 3-hydroxytyrosine 유도체를 합성하고자 L-tyrosine에 Friedel-Craft acyl화, 에스테르화, 아민의 보호기화 및 Baeyer-Villiger 반응들을 행하였다. 또한 특이한 아미노산인 $\beta$-hydroxytyrosine의 합성을 위해 출발물질로 p-hydroxybenzalde-hyde를 사용하여 6단계에 28%의 수율로 oxazolidinoe acid를 합성하였다. 이로부터 4단계 반응을 행하여 보호된 $\beta$-hydroxy-tyrosine을 52%의 수율로 합성하였다.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1996.04a
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• pp.163-163
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• 1996

Peptide 유도체, 특히 tyrosine을 함유한 peptide 유도체는 항암제 개발을 위한 연구의 관심이 되고 있다. Thiophosphotyrosine을 함유한 peptide는, 종양 발현에 관련되는 여러 효소의 억제제로써, 즉 protein tyrosine kinase(PTK)의 억제제 및 protein tyrosine phosphatase(PTPase)의 억제제 혹은 cytosolic protein의 결합을 방지하는 차단제로 사용할 수 있으며 궁극적으로 항암제 개발에 응용할 수 있다. 이에, t-BOC chemistry를 이용하여 t-BOC-tyrosine을 출발물질로 하고, cyanoethyl 기를 phosphate protecting group으로 사용하여 thiophosphotyrosine을 함유한 peptide 유도체의 합성에 필요한 중요한 중간체 인 N-(tert-butoxycarbonyl)-O-(dicyanoethylthio-phosphene)-L-tyrosine을 합성하였다.

• Korean Journal of Microbiology
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• v.28 no.2
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• pp.174-179
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• 1990

In order to overproduce L-phenylalanine, various kind of regulatory mutants were isolated from parental Escherichia coli K-12. MWEC 83 Producing 7.4g/l of L-phenylalanine has been derived as a tyrosine and tryptophan double auxotrophic mutant. To produce L-phenylalanine without adding L-tyrosine and L-tryptophan, revertant strain MWEC 101 was isolated from MWEC 83. Further various analogues and valine resistant mutants were isolated from MWEC 101. MWEC 101-5 was the most excellent strain that produced 17.9g/l of L-phenylalanine after having been cultivated for 54 hours in 15% glucose medium. It was disclosed that activities of rate-limiting enzymes including chorismate mutase and prephenate dehydratase in MWEC 101-5 were desensitized to 2mM L-phenylalanine in the enzyme reaction mixture and that activities level of 3-deoxy-D-arabino-heptulosonic acid-7-phosphate synthase and prephenate dehydratase were increased more than 20 times over those of the parental strain.

• Proceedings of the KSAR Conference
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• 2002.06a
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• pp.85-85
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• 2002

As an effort to direct differentiation of human embryonic stem cells (hES, MB03) to dopamine-producing neuronal cells, we expressed Nurr-l in hES and examined the expression of tyrosine hydroxylase (TH) after bFGF induction. To introduce Nurr-l, hES cells were maintained in humidified chamber with 5% CO₂ and 95% air in DMEM/Fl2 supplemented with FBS (10%), penicillin (100U/㎖), and streptomycin (100㎍/㎖). (omitted)

• Archives of Pharmacal Research
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• v.21 no.3
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• pp.330-337
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• 1998

N-(tert-Butoxycarbonyl)-O-(dimethythiophosphono)-L-tyrosine (6) and N-(tert-butoxycarbonyl)-O-(dicyanoethylthiophosphono)-L-tyrosine (15) were prepared as intermediates for the synthesis of thiophosphotyrosine-containing peptides. The reactivity and suitability of two compounds for the solid phase or solution phase peptide synthesis utilizing t-Boc chemistry were examined.

• Bulletin of the Korean Chemical Society
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• v.26 no.1
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• pp.91-96
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• 2005

O-(3-[$^{18}$F]Fluoropropyl)-L-tyrosine (L-[$^{18}$F]FPT) was synthesized by nucleophilic radiofluorination followed by acidic hydrolysis of protective groups and evaluated with 9 L tumor bearing rat. L-[$^{18}$F]FPT is an homologue of O-(2-[$^{18}$F]fluoroethyl)-L-tyrosine (L-[$^{18}$F]FET) which recently is studied as a tracer for tumor imaging using positron emission tomography (PET). [$^{18}$F]FPT was directly prepared from the precursor of O-(3-ptoluenesulfonyloxypropyl)- N-(tert-butoxycarbonyl)-L-tyrosine methyl ester. FPT-PET image was obtained at 60 min in 9 L tumor bearing rats. The radiochemical yield of [$^{18}$F]FPT was 0-45% (decay corrected) and the radiochemical purity was more than 95% after HPLC purification. The total time elapsed for the synthesis of [$^{18}$F]FPT was 100 min from EOB (End-of-bombardment). A comparison of uptake studies between [$^{18}$F]FPT and [$^{18}$F]FET was performed. In biodistribution, [$^{18}$F]FPT showed similar pattern with [$^{18}$F]FET in various tissues, but [$^{18}$F]FPT showed low uptake in brain. Furthermore, [$^{18}$F]FPT showed higher tumor-to-brain ratio than [$^{18}$F]FET. In conclusion, [$^{18}$F]FPT seems to be more useful amino acid tracer than [$^{18}$F]FET for brain tumors imaging with PET.

• Journal of the Korean Chemical Society
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• v.56 no.5
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• pp.661-664
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• 2012

• The Korean Journal of Mycology
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• v.14 no.2
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• pp.101-107
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• 1986

The properties of carboxyl proteinase which was contained in Poria cocos (Schw.) Wolf were investigated by means of the purification with 0.65 ammonium sulfate saturation, DEAE cellulose and Sephadex G-75 gel filtration. This enzyme was found to hydrolyze only peptide bond between glutamyl-L-tyrosine of carbobenzoxy-L-glutamyl-L-tyrosine among the synthetic substrates of carbobenzoxy-L-glutamyl-L-tyrosine, hippuryl- L-phenylalanine and hippuryl-L-arginine. This enzyme was inhibited by $Zn^{+2},\;Fe^{+2},\;Ca^{+2},\;CN^{-1},\;P_2O_7^{-4}$ ions, but stimulated by $Hg^{+2}$ ion. Also, this enzyme was inhibited by organic compounds such as L-lysine, L-phenylalanine, hippuryl-L-phenylalanine, diazoacetyl-DL-norleucine methyl ester (DAN) and 1,2-epoxy-3-(P-nitrophenoxy)propane(EPNP). In particular, the activity was inhibited by L-lysine till 20 minutes of preincubation time rapidly, and by DAN in the presence of $Cu^{+2}$ ion more rapidly after 30 minutes than DAN in the absence of $Cu^{+2}$ ion. L-Lysine was found to be a competitive inhibitor and its $K_i$ value was determined to be 0.12 mmole by Dixon plot.