Lineweaver–Burk Signature of Non-competitive Inhibition: Which change is characteristic?

Introduction:
Interpreting Lineweaver–Burk plots is central to distinguishing inhibition modes. Non-competitive inhibition has a specific graphical fingerprint that reflects a reduction in catalytic capacity (Vmax).

Given Data / Assumptions:

• True non-competitive case (inhibitor binds E and ES equally well).
• Michaelis–Menten kinetics; plotting 1/v vs 1/[S].

Concept / Approach:

In the non-competitive limit, Vmax decreases; Km remains essentially unchanged. On a double-reciprocal plot, this means 1/Vmax (y-intercept) increases, x-intercept (−1/Km) is nearly constant, and slope = Km/Vmax increases accordingly. Lines for different inhibitor levels intersect on or near the x-axis.

Step-by-Step Solution:

Verification / Alternative check:

Families of LB lines under non-competitive inhibition commonly intersect on the x-axis; kinetic fitting to v = (Vmax/(1+I/Ki)) * S / (Km + S) reproduces the same geometry.

Why Other Options Are Wrong:

A: No uniform lateral shift occurs. C: x-intercept alone does not change; y-intercept does. D: They are not equally correct; only one statement matches the canonical pattern. E: Vmax does not increase; slope does not decrease.

Common Pitfalls:

Confusing non-competitive with competitive (y-intercept constant in competitive) or uncompetitive (both intercepts shift).

Final Answer:

The y-intercept (1/Vmax) increases while the x-intercept (−1/Km) remains approximately unchanged.