Factors Affecting Enzyme Activity

The amount of enzyme present directly affects the reaction speed, provided substrate is abundant.

Enzymes bind only specific substrates because of their shape, like a lock and key.

Enzymes speed up reactions by binding to substrates, facilitating the reaction, and releasing products, without changing themselves.

Equation describing how reaction speed changes with substrate concentration.

Substrate concentration at which the reaction velocity is half of its maximum $V_{max}$. Also shows the affinity of enzyme and substrate.

Certain metals (inorganic cations) boost enzyme activity by interacting with enzyme or substrates.

Processes that decrease or stop the activity of an enzyme.

An inhibitor binds to the same site as the substrate, competing with it for the active site of the enzyme.

The ability of an enzyme to catalyze a reaction.

Enzyme activity is optimal at a specific temperature. High temperatures cause denaturation, while low temperatures reduce collisions.

Enzymes function best at a specific pH. Changes in pH can disrupt enzyme structure, affecting activity.

Increasing substrate concentration boosts enzyme reaction rate until a maximum velocity is reached.

Increasing enzyme concentration raises the reaction rate, as more enzymes are available to catalyze the reaction.

Enzyme activity adjustment by binding a substance at a site other than the active site.

A regulatory mechanism where a final product of a metabolic pathway inhibits an earlier enzyme.

The temperature at which an enzyme functions most efficiently and rapidly.

The process in which proteins lose their 3D structure and activity due to high temperatures or other extreme conditions.

A type of enzyme inhibition where the inhibitor permanently binds to the enzyme, essentially disabling it.

Irreversible inhibitors often target and block the enzyme's active site, preventing substrate binding and reaction.

A special type of irreversible inhibitor that binds to the enzyme and triggers its own destruction, effectively self-destructing the enzyme.

A type of enzyme inhibition where the inhibitor binds temporarily to the enzyme, allowing for reversible interactions.

A type of inhibition where the inhibitor binds to a site other than the active site, changing the enzyme's shape and affecting its ability to bind the substrate.

The process where an enzyme loses its shape and function due to factors like extreme temperature or pH.

Glucokinase is a specific enzyme found in the liver, while hexokinase is found in most tissues. Both phosphorylate glucose, but glucokinase has a higher Km and is not inhibited by glucose-6-phosphate, allowing it to function at high glucose levels.

The substrate concentration at which the reaction velocity is half of its maximum (Vmax). It reflects the enzyme's affinity for its substrate.

Certain metal ions (like chloride) can enhance enzyme activity by interacting with the enzyme or substrate.

Statins are a class of drugs that lower cholesterol levels in the blood by inhibiting the enzyme HMG-CoA reductase. This enzyme is crucial for the synthesis of cholesterol in the liver.

Allopurinol is a drug used to treat gout. It works by inhibiting the enzyme xanthine oxidase, which is involved in the breakdown of purines, a type of base in DNA and RNA. This reduces the production of uric acid, the culprit behind gout.

Methotrexate is a chemotherapy drug that inhibits the enzyme dihydrofolate reductase. This enzyme is essential for the synthesis of DNA and RNA. By blocking this enzyme, methotrexate hinders cell growth and division, slowing down cancer.

Captopril and enalapril are ACE inhibitors, meaning they block the enzyme angiotensin-converting enzyme (ACE). ACE converts angiotensin I to angiotensin II, a powerful vasoconstrictor. By inhibiting ACE, these drugs lower blood pressure.

Dicoumarol is a blood thinner that acts by inhibiting vitamin K epoxide reductase. This enzyme is needed to activate vitamin K, which is essential for blood clotting. By inhibiting this enzyme, dicoumarol prevents blood clotting.

Allosteric enzymes are enzymes that have two binding sites: one for the substrate and one for a modulator (inhibitor or activator). The modulator binds to the allosteric site, triggering a shape change in the enzyme that affects its activity.

Drugs used to treat methanol or ethylene glycol poisoning act as uncompetitive inhibitors. They bind to the enzyme-substrate complex formed by the alcohol dehydrogenase enzyme and the toxic alcohol, preventing its breakdown.