In a clinical setting, an enzyme with a small Km is observed. What might this suggest about the enzyme's role in metabolism?

• A. The enzyme is only active at high substrate concentrations.
• B. The enzyme's role in metabolism is negligible.
• C. The enzyme is inefficient and likely non-functional in metabolism.
• D. The enzyme is likely to be efficient at low substrate concentrations, indicating a regulatory role.

Answer: (D)