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.

---

Definitions:

Line of Credit

A flexible loan from a bank or financial institution that offers a maximum loan balance that can be used over time.

Demand Note

A short-term loan that must be repaid (both principal and interest) in a lump sum at maturity.

Compounding

The process where the value of an investment increases because the earnings on an investment, both capital gains and interest, earn interest as time passes.

Demand Note

A loan or debt instrument that is repayable on demand at the choice of the lender at any time.