Enzyme inhibition

What is a drug?

A biologically active compound that acts as the active pharmaceutical ingredient of a medicine.

What is the therapeutic target of ACE inhibitors?

The angiotensin‑converting enzyme (ACE).

What does ACE convert?

Angiotensin I into angiotensin II.

What does angiotensin II do?

Causes vasoconstriction and stimulates aldosterone release.

How do ACE inhibitors lower blood pressure?

By reducing angiotensin II formation

What adverse effect is associated with ACE inhibitors?

Persistent dry cough.

Why do ACE inhibitors cause cough?

They prevent bradykinin breakdown

What are examples of ACE inhibitors?

Captopril

What is a drug target?

A protein that a drug binds to in order to exert its effect.

What types of proteins can drugs inhibit?

Enzymes

What is reversible inhibition?

Non‑covalent binding of inhibitor to enzyme.

What is irreversible inhibition?

Covalent binding that permanently inactivates the enzyme.

What is competitive inhibition?

Inhibitor competes with substrate for the active site.

What is uncompetitive inhibition?

Inhibitor binds only to the enzyme‑substrate complex.

What is mixed inhibition?

Inhibitor binds to enzyme or ES complex

What is non‑competitive inhibition?

A special case of mixed inhibition where Vmax decreases but Km stays the same.

What is Km?

Substrate concentration at which reaction velocity is half Vmax.

What does Km measure?

The affinity of an enzyme for its substrate.

How is Km determined experimentally?

By measuring initial velocity at different substrate concentrations.

What is V0?

The initial reaction velocity.

Why is the Lineweaver‑Burk plot used?

To linearise the Michaelis‑Menten equation for easier determination of Km and Vmax.

What does the x‑intercept of a Lineweaver‑Burk plot represent?

−1/Km.

What does the y‑intercept of a Lineweaver‑Burk plot represent?

1/Vmax.