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Issue 18, 2005
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Synthesis of (6R)- and (6S)-5,10-dideazatetrahydrofolate oligo-γ-glutamates: Kinetics of multiple glutamate ligations catalyzed by folylpoly-γ-glutamate synthetase

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Abstract

Folylpoly-γ-glutamate synthetase (FPGS, EC 6.3.2.17) catalyzes the ATP-dependent ligation of glutamic acid to reduced folates including (6S)-5,6,7,8-tetrahydrofolate (H4PteGlu), as well as to anticancer drugs such as 5,10-dideaza-5,6,7,8-tetrahydrofolate ((6R)-DDAH4PteGlu1, (6R)-DDATHF, Lometrexol™). Synthesis of unlabeled mono- and polyglutamates, DDAH4PteGlun (6R, n = 1–6; 6S, n = 1–2), as well as (6R)-DDAH4Pte[14C]Glu1, was effected from (6R)- or (6S)-5,10-dideazatetrahydropteroyl azide and glutamic acid, H-Glu-γ-Glun-γ-Glu-OH (n = 0–4), or [14C]glutamic acid, respectively. These compounds were evaluated as FPGS substrates to determine steady-state kinetic constants. Michaelis–Menten kinetics were observed for (6R)-DDAH4PteGlu1, the isomer corresponding to H4PteGlu, whereas marked substrate inhibition was observed for (6S)-DDAH4PteGlun (n = 1–2) and (6R)-DDAH4PteGlun (n = 2–5), but not (6R)-DDAH4PteGlu6. Multiple ligation of glutamate renders a quantitative analysis of these data difficult. However, approximate values of KM = 0.65–1.6 µM and KI = 144–417 µM for DDAH4PteGlun were obtained using a simple kinetic model.

Graphical abstract: Synthesis of (6R)- and (6S)-5,10-dideazatetrahydrofolate oligo-γ-glutamates: Kinetics of multiple glutamate ligations catalyzed by folylpoly-γ-glutamate synthetase

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The article was received on 26 Apr 2005, accepted on 20 Jul 2005 and first published on 15 Aug 2005


Article type: Paper
DOI: 10.1039/B505907K
Citation: Org. Biomol. Chem., 2005,3, 3388-3398
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    Synthesis of (6R)- and (6S)-5,10-dideazatetrahydrofolate oligo-γ-glutamates: Kinetics of multiple glutamate ligations catalyzed by folylpoly-γ-glutamate synthetase

    J. W. Tomsho, J. J. McGuire and J. K. Coward, Org. Biomol. Chem., 2005, 3, 3388
    DOI: 10.1039/B505907K

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