Carbonic anhydrase has two substrates, carbon dioxide and bicarbonate, which are both converted to carbonic acid. Kinetic data for each is given below. While determining the kinetics of HCO₃^- as a substrate, how would the addition of CO₂ effect the reaction if the rate were measured by the disappearance of bicarbonate? Substrate K_m (mM) K_cat (sec^-1) K_cat/K_m (m M^-1sec^-1) CO₂HCO₃^- 12 26 1×10⁶ 4×10⁵ 8)3×10⁴1.5×10⁴ A) CO₂ would increase the activity of the enzyme B) CO₂ would cause an apparent decrease in the K_m for HCO₃^- C) CO₂ would act as a noncompetitive inhibitor D) CO₂ would act as a competitive inhibitor E) none of the above

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Quizplus · Accepted Answer

Based on the given kinetic data, CO₂ could act as a competitive inhibitor. A competitive inhibitor binds to the active site of the enzyme, competing with the substrate binding. This type of inhibitor can be overcome by increasing the concentration of substrate. In this case, CO₂ would be competing with HCO₃^- for binding to the active site of the enzyme. As a result, the apparent K_m for HCO₃^- would decrease in the presence of CO₂. Therefore, the addition of CO₂ would affect the reaction as an apparent decrease in K_m for HCO₃^-.

Carbonic Anhydrase Has Two Substrates, Carbon Dioxide and Bicarbonate, Which