## Competitive Inhibition Characteristics **Key Point:** Competitive inhibitors compete with substrate for the active site of the enzyme. The inhibitor and substrate have similar structural features and bind to the same site. ### Kinetic Parameters | Parameter | Effect | Mechanism | |-----------|--------|----------| | V_max | Unchanged | Inhibitor can be outcompeted by increasing substrate concentration | | K_m | Increased | Requires higher substrate concentration to achieve half-maximal velocity | | Lineweaver-Burk Plot | Parallel lines intersecting on y-axis | All lines meet at 1/V_max | **High-Yield:** The defining feature is that **increasing substrate concentration can overcome the inhibition** — this is the hallmark of competitive inhibition and distinguishes it from non-competitive and uncompetitive types. ### Lineweaver-Burk Equation $$\frac{1}{V} = \frac{K_m(1 + \frac{[I]}{K_i})}{V_{max}} \cdot \frac{1}{[S]} + \frac{1}{V_{max}}$$ With competitive inhibition, the slope increases (due to increased K_m) but the y-intercept (1/V_max) remains constant. **Clinical Pearl:** Statins (competitive inhibitors of HMG-CoA reductase) and ACE inhibitors are classic examples of competitive inhibition used therapeutically. **Mnemonic:** **CIC** — **C**ompetitive inhibition: **I**nhibitor competes for active site, **C**an be overcome by substrate.
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