5. An enzyme shows strong substrate specificity, yet mutation of a single active‑site residue leads to a dramatic increase in catalytic rate but a decrease in substrate affinity. Which interpretation best fits this observation? (A)The mutation stabilizes the enzyme–substrate complex but destabilizes the transition state (B)The mutation decreases the activation energy but weakens binding interactions in the active site (C)The mutation increases both kcat and KM by stabilizing the transition state (D)The mutation eliminates a key catalytic group but improves substrate recognition