A chemotherapy drug is an inhibitor of an enzyme in cancer cells. Write a chemic

Question

A chemotherapy drug is an inhibitor of an enzyme in cancer cells. Write a chemical equation for the binding equilibria for Inhibitor (I) binding to an enzyme target to form a complex (E#I). Then write the expression for the binding equilibrium constant, Kj. B. II this molecule binds to the enzyme with the following NCI's and free energies of interaction, what is the total AG degree for binding? What is sign and why? Use space to right as needed. C. From delta G degree, calculate the value of Keq and show your work. The Inhibitor from one H-bond via a carbonyl group to a Serine R-group of the enzyme Draw the two H-bond partners engaged in a H-bond and show the net arrows for the functional groups involved, and label the H-bond partners using the proper terminology.

Explanation / Answer

The Michaelis-Menten expression for mixed inhibition under steady state approximation is as follows:

For example, an enzyme catalyzed mixed inhibition reaction is as follows:

…… (1)

In the above reaction signifies a reversible inhibitor, and called inhibitory dissociation constants. Therefore,

         …… (2)

           …… (3)

In mixed inhibition, the inhibitor bind to the free enzyme and enzyme-substrate complex, then form enzyme-inhibitor and enzyme-substrate-inhibitor complex.

    …… (4)

From the steady state approximation the is,

     …… (5)

…… (6)

Substitute equation (4) in equation (6),

…… (7)

Substitute equation (2), (3) and (5) in equation (7), then by generalization, gives:

If the total inhibitor concentration is much greater than the total enzyme concentration,  

Thus, the Michaelis-Menten expression for mixed inhibition under steady state approximation is

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