When enzyme rate, the constraint on the ratio of k cat/Km must be kept in mind. Which values of the two constants, respectively, will give the greatest enzyme rate at a given substrate concentration?
A) 1 s -1 / 10-6 M
B) 102 s -1 / 10-4 M
C) 103 s -1 / 10-3 M
D) 104 s -1 / 10-2 M
E) 105 s -1 / 10-1 M

Question

Quizplus · Accepted Answer

The enzyme rate is given by the equation:

enzyme rate = kcat [enzyme] [substrate]/(Km + [substrate])

To maximize the enzyme rate at a given substrate concentration, we need to maximize the kcat/Km ratio. This can be achieved by increasing either the kcat or decreasing the Km, or both.

Among the given options, the highest kcat/Km ratio is for option E, 105 s-1 / 10-1 M, which gives a ratio of 106 M-1 s-1. This is higher than any of the other options.

Therefore, the best choice to give the greatest enzyme rate at a given substrate concentration is E.

When Enzyme Rate, the Constraint on the Ratio of K