The pancreatic glucokinase of a patient with MODY had a mutation replacing a leucine with a proline. The result was that the Km for glucose was decreased from a normal value of 6 mM to a value of 2.2...

The pancreatic glucokinase of a patient with MODY had a mutation replacing a leucine with a proline. The result was that the Km for glucose was decreased from a normal value of 6 mM to a value of 2.2 mM, and the Vmax was changed from 93 units/mg protein to 0.2 units/mg protein. Which of the following best describes the patient’s glucokinase compared with the normal enzyme?

(A) The patient’s enzyme requires a lower concentration of glucose to reach 1 ⁄2 Vmax. (B) The patient’s enzyme is faster than the normal enzyme at concentrations of glucose below 2.2 mM. (C) The patient’s enzyme is faster than the normal enzyme at concentrations of glucose above 2.2 mM. (D) At near saturating glucose concentration, the patient would need 90 to 100 times more enzyme than normal to achieve normal rates of glucose phosphorylation. (E) As blood glucose levels increase after a meal from a fasting value of 5 mM to 10 mM, the rate of the patient’s enzyme will increase more than the rate of the normal enzyme.