What experimental data would indicate that an enzyme exhibits allostery rather than simple Michaelis-Menten kinetics?

What experimental data would indicate that an enzyme exhibits allostery rather than simple Michaelis-Menten kinetics?

• A. A linear v vs [S] plot
• B. A sigmoidal v vs [S] plot
• C. A sigmoidal v vs [S] plot and Hill coefficient > 1
• D. A hyperbolic v vs [S] plot

Answer: (C)

Cooperativity among subunits drives allosteric regulation, which shows up as a sigmoidal (S-shaped) velocity versus substrate curve. This shape reflects positive cooperativity: binding of substrate at one site increases the affinity at others, causing a steeper response as [S] increases. The Hill coefficient quantifies this effect; a value greater than 1 indicates positive cooperativity and is a hallmark of allostery. Michaelis-Menten kinetics, by contrast, produces a hyperbolic velocity–substrate plot, consistent with non-cooperative binding. So the strongest experimental indication that an enzyme is allosteric is a sigmoidal v vs [S] curve accompanied by a Hill coefficient greater than 1. If you only see a sigmoidal curve without the Hill analysis, it still points to cooperativity, but the Hill coefficient provides a quantitative confirmation.

Cooperativity among subunits drives allosteric regulation, which shows up as a sigmoidal (S-shaped) velocity versus substrate curve. This shape reflects positive cooperativity: binding of substrate at one site increases the affinity at others, causing a steeper response as [S] increases. The Hill coefficient quantifies this effect; a value greater than 1 indicates positive cooperativity and is a hallmark of allostery.

Michaelis-Menten kinetics, by contrast, produces a hyperbolic velocity–substrate plot, consistent with non-cooperative binding. So the strongest experimental indication that an enzyme is allosteric is a sigmoidal v vs [S] curve accompanied by a Hill coefficient greater than 1. If you only see a sigmoidal curve without the Hill analysis, it still points to cooperativity, but the Hill coefficient provides a quantitative confirmation.