A Liver Enzyme Called Two-Substrate Inactivates a Drug by the Following

question 20

Multiple Choice

A liver enzyme called two-substrate inactivates a drug by the following reaction, where NADP is nicotinamide adenine dinucleotide phosphate and NADPH is the reduced form of NADP: Drug + NADPH ? Inactive product + NADP⁺
The Km and physiological substrate concentrations (both in millimoles per liter) are given in the table for both substrates.
What is the rate-limiting substrate under these conditions, and what is the derived Michaelis-Menten equation that describes the velocity of product formation by the enzyme?

• A)Drug limiting; vo = Vmax.
• B)NADPH limiting; 1/2 Vmax.
• C)NADPH limiting; (Vmax x [NADPH])/0.22 mmol.
• D)Drug limiting; (Vmax x [Drug])/0.12 mmol.
• E)NADPH limiting; k2/Km.

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