Proenzymes are active/inactive enzyme precursors.

Explanation

**Step-by-Step Solution:**

1. **Definition of Proenzymes**: Proenzymes, also known as zymogens, are precursors to enzymes that are initially inactive. They are synthesized in an inactive form to prevent premature activation and potential damage to the cells or tissues.

2. **Function of Proenzymes**: Proenzymes require a biochemical change to become active enzymes. This change usually involves the cleavage of specific peptide bonds, which leads to a conformational change in the protein structure, activating the enzyme.

3. **Examples of Proenzymes**:
- **Pepsinogen**: This is the inactive form of the enzyme pepsin, which is involved in protein digestion. Pepsinogen is converted to pepsin in the acidic environment of the stomach.
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