**Core Concept**
The question requires identification of an enzyme inhibitor, which is a type of pharmacological agent that blocks the action of an enzyme. Enzyme inhibitors are used in various therapeutic areas, including cardiovascular disease, cancer, and metabolic disorders.

**Why the Correct Answer is Right**
The mechanism of enzyme inhibition involves binding to the active site of the enzyme, thereby preventing the substrate from binding and reducing the enzyme's activity. This can be achieved through competitive inhibition, where the inhibitor competes with the substrate for the active site, or non-competitive inhibition, where the inhibitor binds to an allosteric site and alters the enzyme's conformation. Examples of enzyme inhibitors include ACE inhibitors, which are used to treat hypertension and heart failure.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is not a known enzyme inhibitor.
**Option B:** This option is incorrect because it is a type of enzyme activator, not an inhibitor.
**Option C:** This option is incorrect because it is a type of substrate, not an enzyme inhibitor.

**Clinical Pearl / High-Yield Fact**
It is essential to understand the mechanism of enzyme inhibition to appreciate the therapeutic effects of enzyme inhibitors. For example, ACE inhibitors work by inhibiting the angiotensin-converting enzyme (ACE), which is responsible for converting angiotensin I to angiotensin II, a potent vasoconstrictor.

**Correct Answer: C.**