Enzyme Regulation and Inhibition

1. Feedback Control

2. Allosteric Enzymes

3. Proteolytic Enzymes & Zymogens

4. Covalent Modification

5. Compartmentalization

What are the 5 common mechanisms of regulation?

Feedback Inhibition / Feedback Control

It is a process in which the end product of a reaction inhibits or controls the enzyme that helped produce it

Allostery

means “another site”

Allosteric Regulation

Control of enzyme activity when a molecule (effector/modulator) binds to a site other than the active site (allosteric site)

Allosteric/ Regulatory site

It is where the modulator binds

False, it does change the enzyme’s kinetic properties

T/F

The binding of the modulator does not change the enzyme’s kinetic properties

Activator / Positive regulator

• It binds to the regulatory site

• It changes the shape of the enzyme, which makes the active site be able to accommodate the substrate

Inhibitor / Negative regulator

• It binds to the regulatory site

• It distorts/changes the active site, which will make the substrate no longer fit

Proteolytic enzymes

Enzymes that cleaves proteins

Zymogens

Inactive form of proteolytic enzymes

Typsin, Chymotrypsin, Pepsin

Examples of zymogens

Covalent Modification

This regulates enzyme activity by forming or breaking covalent bonds to attach or remove specific chemical groups

Compartmentalization

• Cellular membranes compartmentalize reactions, allowing different environments to be maintained for different processes

• It allows segregation of metabolic processes (catabolic from anabolic and vice versa)

• Specific enzymes can also be restricted to specific organelles to perform specialized functions

1. Irreversible

2. Reversible

Two types of enzyme inhibition

1. Competitive

2. Noncompetitive

3. Uncompetitive

3 types of Reversible Inhibition

Inhibitors

These are compounds that cause enzymes to lose activity by slowing down or stopping the chemical reaction

Competitive Inhibition

In this type of inhibition, the inhibitor competed with the substrate for the enzyme’s active site

True

T/F

In competitive inhibition, ↑amount of substrate = can overcome the inhibition

Noncompetitive Inhibition

In this type of inhibition, The inhibitor binds at a regulatory/other site, rather than competing directing for the active site

False, inhibition still happens

T/F

In noncompetitive inhibition, the inhibition no longer happens when substrate concentration is increased

Uncompetitive Inhibition

In this type of inhibition, the inhibitor binds only after the enzyme has already bound the substrate

-1/Km = x-intercept

1/Vmax = y-intercept

In Lineweaver-Burk Plot, what are the x and y intercepts?