In Michaelis-Menten kinetics, a competitive inhibitor increases the apparent Km without changing Vmax. The apparent Km is increased because:

• A The inhibitor increases catalytic turnover, requiring more substrate for saturation
• B The inhibitor competes with substrate for the active site; higher substrate concentration is needed to displace the inhibitor and half-saturate the enzyme ✓
• C The inhibitor binds the enzyme-substrate complex, reducing product formation
• D The inhibitor irreversibly modifies the active site, reducing enzyme concentration

Explanation

Competitive inhibitors bind reversibly to the active site, competing directly with substrate; because the inhibitor occupies some active sites, higher substrate concentration is required to achieve half-maximal velocity (apparent Km increases). At saturating substrate, all inhibitor is displaced and Vmax is unchanged. Binding of inhibitor to ES complex defines uncompetitive inhibition (lowers both Km and Vmax). Irreversible modification defines suicide/irreversible inhibitors.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

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