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?

Question

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?

Quizplus · Accepted Answer

The drug concentration is not limiting because it is far higher than the Km.However, the NADPH concentration equals the Km, which implies that the reaction rate is half-maximal.

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