MCB354FA15_PS04 Angiotensin converting enzyme (ACE) catalyzes the formation of a

Question

MCB354FA15_PS04
Angiotensin converting enzyme (ACE) catalyzes the formation of angiotensin II, a potent constrictor of blood vessels. ACE inhibitors are widely used to treat hypertension by reducing vasoconstriction. One such ACE inhibitor is enalapril, a multi-billion dollar per year drug for the treatment of high blood pressure.
ACE has a KM of 12 mM for its substrate, which is present in plasma at a concentration of 75 mM. When enalapril is present at 2.4 nM, the activity of ACE in plasma is 10% of its uninhibited activity. What is the value of Ki for enalapril?

Please explain how to to obtain the answer step by step.

Explanation / Answer

Ans. Given parameters are:

V=10%of Vmax

=1/10 Vmax

[S]= 75mM

[I]= 2.4nm= 2.4x10-6mM

Km= 12mM

It is known hat this is a non competitive inhibition.

Therefore putting values in formula.

V=vmax[S]/Km+[S](1+[i]/Ki)

1/10Vmax=Vmax[75]/(12+[75])(1+0.0000024/Ki)

On solving this equation:

Ki= 3.13X10-7 mM

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