Biochem 5.4 Enzyme Inhibitors Overview

A type of enzyme inhibition where the inhibitor binds permanently to the enzyme, decreasing its activity. This is typically due to irreversible covalent modifications or very tight binding.

A type of enzyme inhibition where the inhibitor binds reversibly to the enzyme's active site, competing with the substrate for binding.

A type of enzyme inhibition where the inhibitor binds reversibly to a site on the enzyme different from the active site, but only to the enzyme-substrate complex, not the free enzyme. This binding changes the enzyme's conformation, preventing it from converting the substrate to product.

A type of enzyme inhibition where the inhibitor binds reversibly to the enzyme at an allosteric site, changing the enzyme's conformation and affecting its affinity for both substrate and product.

A special case of mixed inhibition where the inhibitor binds to the enzyme with equal affinity whether or not the substrate is present.

The process of synthesizing more of an enzyme to compensate for the loss of activity due to irreversible inhibition.

A measure of how tightly an inhibitor binds to an enzyme, with a lower Ka value indicating stronger binding.

A type of reversible enzyme regulation where the inhibitor binds non-covalently to the enzyme, inducing conformational changes that affect the enzyme's activity.

A substrate analog that structurally resembles the substrate but does not undergo a reaction after binding to the enzyme.

A noncompetitive inhibitor's special property where the binding of the substrate and the inhibitor happens independently, without affecting each other.

The site on an enzyme where the substrate binds, also called the active site.

A site on an enzyme different from the active site where inhibitors can bind to change the enzyme's activity.

The graphical representation of enzyme kinetics, plotting initial reaction velocity (V₀) against substrate concentration ([S]).

A plot that linearizes the Michaelis-Menten plot, making it easier to analyze enzyme kinetics and inhibition.

A plot showing the relationship between initial velocity (V₀) and substrate concentration ([S]).

Mixed inhibitors that increase the apparent Km. They bind to the enzyme and decrease the maximum velocity but do NOT increase the apparent Km.

Mixed inhibitors that decrease the apparent Km. They bind to the enzyme and decrease the maximum velocity but do NOT increase the apparent Km.

The apparent Km of the enzyme is increased when a competitive-like mixed inhibitor is present.

The apparent Km of the enzyme is decreased when an uncompetitive-like mixed inhibitor is present

On a Lineweaver-Burk plot, uncompetitive inhibition causes the x-intercept (representing -1/$K_m$) to shift left and the y-intercept (representing 1/$V_{max}$) to shift upward, resulting in parallel lines for uninhibited and inhibited data.

On a Lineweaver-Burk plot, noncompetitive inhibition causes the y-intercept (representing 1/$V_{max}$) to shift upward, while the x-intercept (representing -1/$K_m$) remains unchanged.

Noncompetitive inhibitors are a special type of mixed inhibitor, where the inhibitor binds to the enzyme with the same affinity whether or not the substrate is bound.

Mixed inhibition can appear similar to uncompetitive inhibition on a Michaelis-Menten plot, but the distinction is that $V_{max}$ and $K_m$ change by different factors in mixed inhibition.

Uncompetitive inhibitors are difficult to distinguish from mixed inhibitors with similar effects on Michaelis-Menten plots. Lineweaver-Burk plots provide clearer visual differences.