In a Lineweaver-Burk (double-reciprocal) plot, a pure non-competitive inhibitor produces which pattern?

• A Lines intersecting the x-axis at the same point but with steeper slopes; same x-intercept
• B Lines that intersect to the left of the y-axis (same x-intercept) and above the x-axis
• C Lines with same x-intercept (-1/Km) but different y-intercepts (1/Vmax increases) ✓
• D Parallel lines with different y-intercepts but same slope

Explanation

Non-competitive inhibitors bind the enzyme at a site distinct from the active site (to both free enzyme and ES complex equally), reducing Vmax without affecting substrate binding (Km unchanged). On a Lineweaver-Burk plot, this produces lines that cross the x-axis at the same point (-1/Km unchanged) but have higher y-intercepts (1/Vmax increases) — i.e., they intersect ON the x-axis. Competitive inhibitor lines intersect on the y-axis (same Vmax). Uncompetitive inhibitors produce parallel lines.

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

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