PMID:15158730
| Citation |
MacDonnell, JE, Lunn, FA and Bearne, SL (2004) Inhibition of E. coli CTP synthase by the "positive" allosteric effector GTP. Biochim. Biophys. Acta 1699:213-20 |
|---|---|
| Abstract |
Cytidine 5'-triphosphate (CTP) synthase catalyzes the ATP-dependent formation of CTP from UTP using either ammonia or l-glutamine as the source of nitrogen. When glutamine is the substrate, GTP is required as a positive allosteric effector to promote catalysis of glutamine hydrolysis. We show that at concentrations exceeding approximately 0.15 mM, GTP actually behaves as a negative allosteric effector of E. coli CTP synthase, inhibiting glutamine-dependent CTP formation. In addition, GTP inhibits NH(3)-dependent CTP formation in a concentration-dependent manner. However, GTP does not inhibit the enzyme's intrinsic glutaminase activity. Although the activation of CTP synthase by GTP does not display cooperative behavior, inhibition of both CTP synthase-catalyzed ammonia- and glutamine-dependent CTP synthesis by GTP do exhibit positive cooperativity. These results suggest that GTP binding affects CTP synthase catalysis in two ways: it activates enzyme-catalyzed glutamine hydrolysis and it inhibits the utilization of NH(3) as a substrate by the synthase domain. |
| Links |
PubMed Online version:10.1016/j.bbapap.2004.03.002 |
| Keywords |
Allosteric Regulation; Ammonia/metabolism; Carbon-Nitrogen Ligases/antagonists & inhibitors; Cytidine Triphosphate/biosynthesis; Escherichia coli/enzymology; Glutaminase/antagonists & inhibitors; Glutamine/metabolism; Guanosine Triphosphate/metabolism; Guanosine Triphosphate/pharmacology; Hydrolysis; Kinetics; Uridine Triphosphate/metabolism; Uridine Triphosphate/pharmacology |
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