Calculate enzyme reaction velocity under noncompetitive inhibition conditions using Vmax, Km, substrate concentration, inhibitor concentration, and Ki values.
Reaction Velocity (v)
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Inhibition Factor
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Percent Inhibition
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Apparent Vmax
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Noncompetitive inhibition occurs when an inhibitor binds to a site other than the active site, reducing enzyme activity without affecting substrate binding. The inhibitor can bind to both the free enzyme and the enzyme-substrate complex.
In noncompetitive inhibition, the inhibitor doesn't compete with substrate for the active site. Instead, it binds to an allosteric site, reducing Vmax but leaving Km unchanged. Competitive inhibitors increase Km but don't affect Vmax.
Ki is the dissociation constant for inhibitor binding, representing the inhibitor concentration at which half the enzyme molecules are bound by inhibitor. Lower Ki values indicate stronger inhibitor binding and more potent inhibition.
The velocity is calculated using: v = (Vmax × [S]) / ((Km + [S]) × (1 + [I]/Ki)). The inhibitor affects the denominator by the factor (1 + [I]/Ki), reducing the overall reaction rate.
The inhibition factor (1 + [I]/Ki) shows how much the enzyme activity is reduced by the inhibitor. A factor of 2 means the enzyme operates at half its normal activity under those conditions.
No, unlike competitive inhibition, noncompetitive inhibition cannot be overcome by increasing substrate concentration. The inhibitor effect remains constant regardless of substrate levels.
Ki values vary widely depending on the inhibitor and enzyme system. Strong inhibitors may have Ki values in the nanomolar range (nM), while weaker inhibitors have Ki values in the micromolar (μM) or millimolar (mM) range.
This calculator helps researchers evaluate potential drug compounds as enzyme inhibitors. By determining Ki values and inhibition percentages, scientists can compare inhibitor potency and optimize compound design for therapeutic applications.