Mevastatin is a cholesterol lowering drug whose mechanism of action is the inhib

Question

Mevastatin is a cholesterol lowering drug whose mechanism of action is the inhibition of HMG-CoA reductase. If a patient takes a 10.0 mg dose of mevastatin, what is the concentration of mevastatin in the blood? Assume the patient has 5.0 L of blood. The molecular weight of mevastatin is 408. Mevastatin is a competitive inhibitor of HMG-CoA reductase with a K_i of 1.4 Times 10^-3 mu M. What fraction of the enzyme will have a bound substrate under the conditions described above? Assume the concentration of HMG-CoA is 15 mu M, and the K_M for HMG-CoA reductase is 1.4 mu M. After a period of time, all but 0.10% of the mevastatin in the blood is metabolized. What fraction of the enzyme will have bound substrate under these conditions?

Explanation / Answer

1. concentration of mevastatin=10/(408*5)*1000=4.902 µM.

2. For the competitive inhibitor [ES]/ [Et] = [S]/ Km (1 I/Ki) + [S]=15/(15+1.4(1+4.902/1.4))=0.704

3. fraction=ES]/ [Et] = [S]/ Km (1 I/Ki) + [S]=15/(15+1.4(1+.4902/1.4))=0.888

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