Which type of enzyme inhibitor does not alter the \(K_m/V_{max}\) ratio of an enzyme?

• A. Uncompetitive inhibitor
• B. Competitive inhibitor
• C. Noncompetitive inhibitor
• D. Allosteric inhibitor

Answer: (C)

Verified step by step guidance

1. Understand the concept of enzyme kinetics: Enzyme inhibitors affect the activity of enzymes by interacting with them in various ways. The \(K_m\) (Michaelis constant) and \(V_{max}\) (maximum velocity) are key parameters in enzyme kinetics that describe the enzyme's efficiency and capacity.
2. Define the types of enzyme inhibitors: Competitive inhibitors bind to the active site of the enzyme, uncompetitive inhibitors bind only to the enzyme-substrate complex, noncompetitive inhibitors bind to a site other than the active site, and allosteric inhibitors regulate enzyme activity by binding to allosteric sites.
3. Analyze the effect of noncompetitive inhibitors: Noncompetitive inhibitors decrease the \(V_{max}\) because they reduce the overall number of active enzyme molecules, but they do not affect the \(K_m\) since the substrate binding affinity remains unchanged. This means the \(K_m/V_{max}\) ratio remains constant.
4. Compare with other inhibitors: Competitive inhibitors increase the \(K_m\) without affecting \(V_{max}\), uncompetitive inhibitors decrease both \(K_m\) and \(V_{max}\) proportionally, and allosteric inhibitors can have varied effects depending on whether they are activators or inhibitors.
5. Conclude that noncompetitive inhibitors are the type of enzyme inhibitor that does not alter the \(K_m/V_{max}\) ratio, as their mechanism of action specifically impacts \(V_{max}\) without changing \(K_m\).