Final answer:
An enzyme is inactivated when it loses its native conformation and biological activity. The active site of an enzyme is crucial for its biological activity, and when an enzyme loses its native conformation, the active site may change and become unable to effectively bind to the substrate.
Step-by-step explanation:
An enzyme is inactivated when it loses its native conformation and its biological activity. This means that it can no longer carry out its normal function. The active site of an enzyme, where the substrate binds and catalysis takes place, is crucial for its biological activity. When an enzyme loses its native conformation, the active site may change and become unable to effectively bind to the substrate, leading to the loss of enzyme activity.