Kinetic properties of ATP phosphoribosyltransferase of escherichia coli
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In the absence of histidine the variation of initial velocity as a function of ATP or phosphoribosyl pyrophosphate (PRPP) concentration, follows Michaelis-Menten kinetics, with ATP inhibiting at high concentrations. In the presence of histidine a change from hyperbolic to sigmoidal kinetics is observed.
Apparently AMP acts as a competitive inhibitor of ATP.
The bisubstrate kinetics gives a pattern of parallel lines, suggesting a double displacement mechanism.
The inhibition by histidine appears not to be cooperative or perhaps slightly negatively cooperative.
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