PMID:12093297
| Citation |
Li, Y, Gong, Y, Shi, G, Blaszczyk, J, Ji, X and Yan, H (2002) Chemical transformation is not rate-limiting in the reaction catalyzed by Escherichia coli 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase. Biochemistry 41:8777-83 |
|---|---|
| Abstract |
6-Hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK) catalyzes the transfer of pyrophosphate from ATP to 6-hydroxymethyl-7,8-dihydropterin (HMDP). Because HPPK is essential for microorganisms but is absent from human and animals, the enzyme is an excellent target for developing antimicrobial agent. Thermodynamic analysis shows that Mg(2+) is important not only for the binding of nucleotides but also for the binding of HMDP. Transient kinetic analysis shows that a step or steps after the chemical transformation are rate-limiting in the reaction catalyzed by HPPK. The pre-steady-state kinetics is composed of a burst phase and a steady-state phase. The rate constant for the burst phase is approximately 50 times larger than that for the steady-state phase. The latter is very similar to the k(cat) value measured by steady-state kinetics. A set of rate constants for the individual steps of the HPPK-catalyzed reaction has been determined by a combination of stopped-flow and quench-flow analyses. These results form a thermodynamic and kinetic framework for dissecting the roles of active site residues in the substrate binding and catalysis by HPPK. |
| Links | |
| Keywords |
Adenosine Triphosphate/analogs & derivatives; Adenosine Triphosphate/metabolism; Adenosine Triphosphate/pharmacology; Catalysis; Escherichia coli/enzymology; Kinetics; Models, Theoretical; Multienzyme Complexes/chemistry; Multienzyme Complexes/metabolism |
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