Enzyme inhibition types template

Competitive, uncompetitive and pure non-competitive inhibition, each with its Lineweaver–Burk lines with and without inhibitor, and a table of apparent Km and Vmax (α and α′ factors, mixed inhibition included).

What the template shows

• Reversible inhibitors told apart by their Lineweaver–Burk plots: what happens to Km and Vmax
• Lineweaver–Burk plots with and without inhibitor
• Solid: no inhibitor (Km = Vmax = 1). Dashed: with inhibitor (α or α′ = 2)
• I binds only free E, at the active site
• Km ↑ (×α), Vmax unchanged
• lines meet on the 1/v₀ axis
• I binds only the ES complex
• Km ↓ and Vmax ↓ (both ÷α′)
• parallel lines
• Non-competitive (pure)
• I binds E and ES equally (α = α′)
• Km unchanged, Vmax ↓ (÷α)
• lines meet on the 1/[S] axis
• Type Inhibitor binds Apparent Km Apparent Vmax Lineweaver–Burk lines Competitive E only αKm (↑) Vmax meet on the y-axis Uncompetitive ES only Km/α′ (↓) Vmax/α′ (↓) parallel Mixed E and ES (α ≠ α′) αKm/α′ Vmax/α′ (↓) meet off both axes Non-competitive E and ES (α = α′) Km Vmax/α (↓) meet on the x-axis
• α = 1 + [I]/Kᵢ (binding to E), α′ = 1 + [I]/Kᵢ′ (binding to ES)
• Competitive inhibition is overcome by enough substrate (Vmax unchanged): malonate on succinate dehydrogenase, methotrexate on dihydrofolate reductase.
• An uncompetitive inhibitor binds only ES, so it lowers Km and Vmax by the same factor; the slope Km/Vmax stays the same and the lines are parallel.
• Pure non-competitive inhibition is the special case of mixed inhibition with α = α′; irreversible inhibitors (e.g. DIFP on serine proteases) instead remove active enzyme.

Drawn with 256 shapes – every one editable in MolDraw.

Sources

• Nelson & Cox, Lehninger Principles of Biochemistry, 8th ed., 2021, ch. 6 Textbook
• Berg, Tymoczko, Gatto & Stryer, Biochemistry, 9th ed., 2019 Textbook
• Voet & Voet, Biochemistry, 4th ed., Wiley 2011 Textbook