Allosteric Inhibition and Enzyme Regulation

The lecture covers enzyme inhibition, focusing on allosteric inhibition. It explains how allosteric inhibition involves a modulator binding to a non-catalytic site, causing conformational changes that affect enzyme activity. The lecture discusses positive and negative cooperativity, the sigmoid curve characteristic of allosteric inhibition, and how it differs from Michaelis-Menten kinetics. Examples like phosphofructokinase and glutamate dehydrogenase illustrate the concept. The session concludes with a preview of feedback inhibition and covalent modification.

What is the primary characteristic of allosteric inhibition?

• No change in enzyme conformation

• Binding at a site other than the active site

• Covalent bonding with the enzyme

• Binding at the active site

In allosteric inhibition, what is the role of a modulator?

• It only binds to the active site

• It can either increase or decrease enzyme activity

• It binds covalently to the enzyme

• It always increases enzyme activity

How does allosteric inhibition differ from Michaelis-Menten kinetics?

• It follows a hyperbolic curve

• It involves covalent interactions

• It results in a sigmoid curve

• It does not involve enzyme conformational changes

What type of curve is associated with allosteric inhibition?

• Exponential

• Sigmoid

• Hyperbolic

• Linear

What is a key feature of K-class allosteric enzymes?

• No change in enzyme kinetics

• Inhibition by substrate

• Change in Vmax

• Change in Km

Which enzyme is an example of a V-class allosteric enzyme?

• Phosphofructokinase

• Aspartate transcarbamoylase

• Acetyl coenzyme A carboxylase

• Glutamate dehydrogenase

What is the effect of citrate on phosphofructokinase?

• It activates the enzyme

• It inhibits the enzyme

• It has no effect

• It binds covalently

Which molecule acts as an activator for phosphofructokinase?

• ATP

• ADP

• AMP

• Citrate

What is the role of ATP in the regulation of glutamate dehydrogenase?

• It binds covalently

• It acts as an activator

• It acts as an inhibitor

• It has no effect

Which of the following is NOT a mode of enzyme regulation discussed in the lecture?

• Competitive inhibition

• Feedback inhibition

• Allosteric inhibition

• Covalent modification