Biology · Simulator 035
An enzyme turns substrate into product. Raise the substrate concentration and the reaction speeds up, until every enzyme is busy. Add an inhibitor and see how competitive and non-competitive inhibition change the curve in different ways.
The Michaelis–Menten equation gives the initial reaction velocity v at substrate concentration [S]:
v = Vmax [S] / (Km + [S])
Vmax is the top speed when the enzyme is saturated. Km is the substrate concentration that gives half of Vmax; a low Km means high affinity.
Inhibitors at concentration [I] with dissociation constant Ki act through the factor α = 1 + [I]/Ki:
The Lineweaver–Burk (double-reciprocal) plot of 1/v against 1/[S] is a straight line. Its intercepts are 1/Vmax and −1/Km, which makes inhibition types easy to tell apart. “Measured” points include optional seeded noise, as in a real assay.
Steady-state, single-substrate kinetics; ignores product inhibition, cooperativity and enzyme denaturation.
A drug is a competitive inhibitor of an enzyme. A patient's tissue has a substrate concentration far above Km. Will the drug work well? What about a non-competitive drug?
At [S] ≫ Km, v ≈ Vmax for a competitive inhibitor, because substrate outcompetes it, so it has little effect. A non-competitive inhibitor lowers Vmax itself, so it still slows the reaction by the factor α, however much substrate there is.