430-530-Lec 9-Enzyme Regulation 2025

What factors affect the rate of enzymatic reactions?

Enzyme concentration, cofactor concentration, substrate concentration, effectors/inhibitors, temperature, and pH.

What happens to enzyme activity at different pH levels?

Changes in pH can alter active site chemistry and disrupt enzyme structure, potentially leading to denaturation.

What is the optimal temperature for most human metabolic enzymes?

37 degrees Celsius.

What is competitive inhibition?

A type of reversible inhibition where an inhibitor competes with the substrate for the active site, increasing apparent KM.

How does non-competitive inhibition affect enzyme kinetics?

It decreases Vmax without affecting KM, as the inhibitor binds to a different site on the enzyme.

What characterizes irreversible inhibitors?

They covalently bind to enzymes, permanently inactivating them.

What is the significance of the Michaelis Constant (KM)?

It is the substrate concentration at which the reaction velocity is half of Vmax and indicates the enzyme’s affinity for a substrate.

Define allosteric regulation of enzymes.

Allosteric regulation involves an effector molecule binding to a site other than the active site, modifying enzyme activity.

What is feedback inhibition?

A regulatory mechanism where the end product of a metabolic pathway inhibits an enzyme involved in its synthesis.

How can enzymes be regulated by covalent modifications?

Through modifications such as phosphorylation, which can activate, inhibit, or modulate enzyme activity.

What happens during the activation of zymogens?

Inactive precursors are converted to active enzymes by proteolytic cleavage.

What is a common characteristic of allosteric enzymes?

They often have multiple binding sites and do not follow Michaelis-Menten kinetics, exhibiting sigmoidal behavior.

What is the role of cooperativity in allosteric enzymes?

Binding of a ligand to one site increases the affinity of other binding sites, a phenomenon known as positive cooperativity.

Describe the actions of suicide inhibitors.

They are converted by the enzyme into a reactive form that then binds irreversibly to the enzyme, effectively inhibiting it.