- Synthesis of deuterium, tritium and 14-carbon labelled isotopomers of L-DOPA
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The synthesis of five isotopomers of L-DOPA labelled selectively with deuterium, tritium and 14C is reported. The isotopomers of L-tyrosine, the intermediate substrates for this synthesis, were obtained using chemical and enzymatic methods. Sel
- Kozlowska,Kanska
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p. 1763 - 1769
(2008/09/17)
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- Synthesis of tritium labeled isotopomers of L-tyrosine
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The synthesis of four selectively labeled isotopomers of L-tyrosine, (L-Tyr), using chemical and enzymatic methods is reported. Four tritium labeled isotopomers of L-phenylalanine (L-Phe) - [2-3H]-, [2′,6′-3H2]-, [3R-3H]- and [3S-3H]- have been synthesized using a combination of chemical and enzymatic methods. The labeled isotopomers of L-Phe have been converted into [2-3H]-, [2′,6′-3H2]-, [3R-3H]-, and [3S-3H]-L-Tyr by using the enzyme L-phenyl-alanine 4′-monooxygenase. Copyright
- Augustyniak,Suchecki,Jemielity,Kanski,Kanska
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p. 559 - 567
(2007/10/03)
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- Steric Course of the Reactions Catalyzed by 5-Enolpyruvylshikimate-3-phosphate Synthase, Chorismate Mutase, and Anthranilate Synthase
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To probe the steric course of several reactions in the shikimate pathway, (1R,2R)-glycerol was synthesized and fed to cultures of Klebsiella pneumoniae mutant 62-1.The accumulated chorismic acid, labeled from endogenously formed (E)-phosphoenolpyruvate, was isolated and degraded by hydrogenation of the side-chain double bond and cleavage of the ether linkage to D,L-lactic-acid.Resolution of the latter and determination of the methyl group configuration in the two enantiomers demonstrated predominant E configuration of the chorismic acid.It follows that the addition and the elimination step in the 5-enolpyruvylshikimate-3-phosphate (ESP) synthase reaction proceed with opposite stereochemistry, i.e., anti/syn or syn/anti.Incubation of the above chorismic acid with anthranilate synthase produced pyruvate of predominantly S configuration, indicating stereospecific protonation on the re face of the side chain.Conversion of the (E)-chorismic acid into phenylalanine and tyrosine with whole cells of E. coli and configurational analysis of these amino acids by conversion into pyruvate carrying a chiral methyl group with phenylalanine hydroxylase and/or tyrosine phenol-lyase indicated that the chorismate mutase reaction proceeds via a chair transition state.
- Asano, Y.,Lee, J. J.,Shieh, T. L.,Spreafico, F.,Kowal, C.,Floss, H. G.
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p. 4314 - 4320
(2007/10/02)
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