Question

Alcohol dehydrogenase (ADH) is and enzyme that can catalyze the oxidation of a number of alcohols to the corresponding aldehyde. Two such reactions are:

ethanol CH₃-CH₂OH ————> CH₃-CHO

butanol CH₃-CH₂-CH₂-CH₂OH ———> CH₃-CH₂-CH₂-CHO

The Km for ethanol is 10^-5M and the Km for butanol is 10^-3M. Both substrates bind at the same active site, and the turnover number for each substrate is the same.

You have two test tubes with the same amounts of enzyme. One tube contains 10^-1M butanol, the other 10^-1M ethanol. Which alcohol will be oxidized faster?

		ethanol
		butanol
		Neither, both will be oxidized at the same rate.

Answer 1

Michaelis-Menten equation can be written as,

V=K_cat[enzyme][S]/(K_m+[S]

K_cat is the turnover number.

[S] is te substrate concentration

[enzyme] is the enzyme concentration.

K_m is the Michaelis-Menten constant.K_m is a measure how well a substrate bind with a enzyme.low K_m value indicates large binding affinity ,high K_m value indicates the enzyme does not bind efficciently with the substrate.

K_m of ethanol is less than K_m of butanol.K_m for ethanol is 10^-5M and K_m for butanol is 10^-3M.

so, V will be higher for ethanol.

ethanol will oxidize faster.