You two have identified mutants of an enzyme that catalyzes a commercially usefu

Question

You two have identified mutants of an enzyme that catalyzes a commercially useful reaction. Both mutants have the same Vmax as the original or wild type (WT) enzyme. However, one mutant has a lower Km for substrate than the WT, the other has a higher Km for substrate. Which mutant is likely to be a “better” (i.e., faster) enzyme for catalyzing the reaction:

Neither. Since they have the same Vmax they will have the same reaction velocities at all substrate concentrations

The lower Km enzyme since it will show greater reaction velocities especially at low concentrations of substrate

The higher Km enzyme since it will show greater reaction velocities especially at higher concentrations of substrate.

Explanation / Answer

Km is that substrate concentration at which Vmax is half. A low Km value means, at less substrate concentration half Vmax will be attained. This further implies that this enzyme has higher affinity for substrate; then only, Vmax will be attained with less substrate concentration only.

So, the enzyme mutant with low Km value is better for catalyzing the reaction.

The correct statement should be: "The lower Km enzyme since it will show greater reaction velocities especially at low concentrations of substrate".

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