Please HELP! You have been studying an enzyme and characterized it finding that
ID: 200225 • Letter: P
Question
Please HELP! You have been studying an enzyme and characterized it finding that its Km is 15.0 mM and the Vmax is 140 µmol/min. You created a point mutation in that only one amino acid was changed in the primary sequence of the enzyme that you are studying and collected the data for it and found that the mutant strain had a Km of 0.150 mM and a Vmax of 1.40 µmol/min.
A. Which enzyme has a higher affinity for the substrate that was used to analyze both enzymes? EXPLAIN!
B. What is the initial velocities of the reaction catalyzed by the non-mutant version and the mutant version using a substrate concentration of 10.0 mM, with units?
Non-Mutant _________________________ Mutant _____________________________
Explanation / Answer
An enzyme with a high Km has a low affinity for its substrate, and requires a greater concentration of substrate to achieve Vmax.
Km for wild-type: 15.0 mM Vmax for wild-type:140 µmol/min
Km for mutant: 0.150 mM Vmax for mutant: 1.40 µmol/min
As the wild-type enzyme has high Km, it has low affinity for its substrate.
As the mutant enzyme has low Km, it has high affinity for its substrate and it requires minimum concentration of substrate to achieve Vmax.
So the point mutation enhanced the affinity of the enzyme.
The initial velocity of reaction catalyzed by non-mutant version:
50 µm/minute, When (S)=Km, Vo=1/2 Vmax
The initial velocity of reaction catalyzed by mutant version:
Approximately 1 µm/minute, when (S)>>Km, Vo=Vmax