Suppose that a mutant enzyme binds a substrate 100 times as tightly as does the native enzyme. What is the effect of this mutation on catalytic rate if the binding of the transition state is unaffected?
To determine the effect of the mutation on catalytic rate, we need to consider the relationship between substrate binding and catalytic rate in enzymatic reactions.
In enzymatic reactions, there are two essential steps: substrate binding and catalysis. The enzyme first binds the substrate, forming an enzyme-substrate complex. Then, the enzyme catalyzes the conversion of the substrate to product.
The mutant enzyme in question binds the substrate 100 times more tightly than the native enzyme. However, the question specifies that the binding of the transition state (the high-energy intermediate state during the reaction) is unaffected. The binding of the transition state is generally considered the rate-determining step because it involves the highest energy and is the slowest step in the reaction.
Given that the binding of the transition state is unaffected, the mutation causing tighter substrate binding will not significantly affect the catalytic rate of the enzyme. This is because the rate at which the enzyme can convert the substrate to product is determined by the rate of the transition state formation rather than the binding of the substrate.
Therefore, the effect of this mutation on catalytic rate, assuming binding of the transition state is unaffected, is minimal.