Enzyme Inhibition Models

competitive inhibition

substance that resembles the normal substrate competes with the substrate for the active site

uncompetitive inhibition

inhibitor binds only to enzyme-substrate complex

noncompetitive inhibitor

A substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing its conformation so that it no longer binds to the substrate.

competitive inhibition graph

Cross at y-axis

Same Vmax

Different Km

Uncompetitive Inhibition Graph

Does not change slope.

Changes Km and Vmax.

Results in vertical shift up and down.

noncompetitive inhibition graph

Cross at x-axis

Changes Vmax

Same Km

Enzyme saturation

occurs when substrate levels are so high that all enzyme molecules are actively engaged in the chemical reaction, and so further increases in substrate concentration do not increase reaction rate.

Vmax

maximum rate of an enzyme-catalysed reaction.

saturation graph

Vmax on a graph

Vmax is the horizontal asymptote that the Michaelis-Menten curve approaches at high substrate concentration.

Km

Substrate concentration at 1/2 Vmax

Mixed Inhibition Graph

Difference of enzymes with high vs low Km

An enzyme with a high Km is not normally saturated with substrate and its activity will vary as the concentration of substrate varies, so that the rate of formation of product will depend on the availability of substrate.

Km

Michaelis constant

Binding affinity

Pharmacophore

the three-dimensional arrangement of atoms or groups of atoms responsible for the biological activity of a drug molecule

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