Enzyme Inhibition Overview

Enzyme activity can be regulated by decreasing or stopping its function.

A substance that reduces or eliminates the rate of enzyme activity.

A type of reversible inhibition where the inhibitor and substrate compete for the same catalytic site on the enzyme.

The inhibitor structurally resembles the substrate and binds to the same active site, competing with the substrate.

Competitive inhibition is reversible, meaning the effect can be overcome by increasing the substrate concentration to outcompete the inhibitor for the active site.

Competitive inhibition does not affect the enzyme's maximum velocity (Vmax) but increases the Michaelis constant (Km).

A type of enzyme inhibition where the inhibitor binds to a site different from the active site, affecting the enzyme's activity.

Non-competitive inhibitors do not resemble the substrate and bind to a different site, typically causing a conformational change in the enzyme.

Non-competitive inhibition is usually irreversible, meaning the inhibitor's effect cannot be reversed by simply adding more substrate.

Non-competitive inhibition decreases the enzyme's maximum velocity (Vmax) but does not affect the Michaelis constant (Km).

Heavy metals like mercury (Hg++) and lead (Pb++) can inhibit enzymes by blocking essential sulfhydryl (-SH) groups.

Inhibition of cofactors can occur by blocking coenzymes or prosthetic groups essential for enzyme activity.

Cyanide (CN-), a strong inhibitor, binds to the iron in the heme group of cytochrome oxidase, blocking its activity.

Chelating agents, like oxalate, can bind to metal ion activators, preventing their interaction with enzymes and disrupting their activity.

Allopurinol is a drug used to treat gout by inhibiting the enzyme xanthine oxidase, which converts xanthine to uric acid, the culprit behind gout.

Dicumarol is a drug used to prevent blood clots by inhibiting vitamin K epoxide reductase, an enzyme involved in prothrombin synthesis, a key component of blood clotting.

Sulfonamides are antibiotics that act as competitive inhibitors of dihydropteroate synthase (DHPS), an enzyme involved in folic acid synthesis in bacteria.

Ethanol can act as a competitive inhibitor of alcohol dehydrogenase, the enzyme that converts methanol to toxic formaldehyde leading to optic neuropathy.

Inhibitors that bind irreversibly to the enzyme, forming a stable complex and effectively inactivating the enzyme.

Competitive inhibition is a reversible type of enzyme inhibition where the inhibitor competes with the substrate for the same active site on the enzyme.

Non-competitive inhibition is a type of enzyme inhibition where the inhibitor binds to a different site on the enzyme, altering its activity.

In competitive inhibition, the inhibitor does not affect the enzyme's maximum velocity (Vmax), but increases the Michaelis constant (Km).

In non-competitive inhibition, the inhibitor decreases the enzyme's maximum velocity (Vmax) but does not affect the Michaelis constant (Km).

Irreversible inhibitors bind covalently to the enzyme, permanently modifying its active site and rendering it inactive.

Competitive inhibitors can be overcome by increasing the substrate concentration, allowing the substrate to outcompete the inhibitor for the active site.

Non-competitive inhibition cannot be overcome by increasing the substrate concentration, as the inhibitor's effect is not directly related to the active site.

Competitive inhibition has a key characteristic: the inhibitor structurally resembles the substrate and binds to the same active site.

Non-competitive inhibition is characterized by inhibitors that do not resemble the substrate and bind to a different site on the enzyme, altering its shape and function.