| Autor: |
Gagyi, Cristina, Bucurenci, Nadia, Sîrbu, Ovidiu, Labesse, Gilles, Ionescu, Mihaela, Ofiteru, Augustin, Assairi, Liliane, Landais, Stéphanie, Danchin, Antoine, Bârzu, Octavian, Gilles, Anne-Marie |
| Předmět: |
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| Zdroj: |
European Journal of Biochemistry; Aug2003, Vol. 270 Issue 15, p3196-3204, 9p |
| Abstrakt: |
The gene encoding Bacillus subtilis UMP kinase (pyrH /smbA ) is transcribed in vivo into a functional enzyme, which represents approximately 0.1% of total soluble proteins. The specific activity of the purified enzyme under optimal conditions is 25 units·mg-1 of protein. In the absence of GTP, the activity of B. subtilis enzyme is less than 10% of its maximum activity. Only dGTP and 3′-anthraniloyl-2′-deoxyguanosine-5′-triphosphate (Ant-dGTP) can increase catalysis significantly. Binding of Ant-dGTP to B. subtilis UMP kinase increased the quantum yield of the fluorescent analogue by a factor of more than three. UTP and GTP completely displaced Ant-dGTP, whereas GMP and UMP were ineffective. UTP inhibits UMP kinase of B. subtilis with a lower affinity than that shown towards the Escherichia coli enzyme. Among nucleoside monophosphates, 5-fluoro-UMP (5F-UMP) and 6-aza-UMP were actively phosphorylated by B. subtilis UMP kinase, explaining the cytotoxicity of the corresponding nucleosides towards this bacterium. A structural model of UMP kinase, based on the conservation of the fold of carbamate kinase and N -acetylglutamate kinase (whose crystals were recently resolved), was analysed in the light of physicochemical and kinetic differences between B. subtilis and E. coli enzymes. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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