In: Chemistry
E. coli asparate transcarbamoylase (ATCase) has a Hill coefficient of 1.7 and Vmax 4.5 uM/min. The definition of Vmax is Kcat * [Etot], where kcat is the rate constant for formation of product. The measured value of kcat for this reaciton, which is determined in the absence of CTP, is 800 1/min. The dissociation constant for the allosteric effector CTP from ATCase is 1 mM. When CTP is bound to ATCase the K(1/2) for asparate is 20 mM; when CTP is not bound to ATCase the K(1/2) for asparate is 5 mM.
a) Calculate what the concentration of total ATCase is under the conditions where Vmax was determined. Calculate how much ATCase is present with CTP bound and how much is present without CTP bound when the CTP concentration is 6 mM. Calculate how much ATCase is present with CTP bound and how much is present without CTP bound when the CTP concentration is 0.3 mM.