Lecture 10 - Control of Enzyme activity Flashcards
What is the upper limit for kcat, and Km?
the diffusion controlled limit (10^9 s-1 M-1)
When is an enzyme considered a perfect catalyst?
When kcat/Km above 10^8 s-1 M-1
What is an enzyme inhibitors?
a compound that binds to an enzyme and reduces its activity
What is an irreversible inhibitor?
an inhibitor that binds covalently to an enzyme
What is a reversible inhibitor?
an inhibitor that does not covalently bind to the enzyme
What type of inhibitor can be competitive or non-competitive?
reversible
What is the benefit of a reversible inhibitor?
It can be released from the enzyme after binding, leaving it in its original condition
What does an irreversible inhibitor react with?
specific amino acid side chain (usually in active site) and covalently bonds
What does an irreversible inhibitor to?
binds to the enzyme and permanently inactivates it
What are the mutually exclusive possibilities in competitive inhibition?
E + S -> ES or E + I -> EI
What happens to Vmax and Km with competitive inhibition?
- Vmax is the same (because infinite substrate would outcompete the inhibitor)
- Km increases (more substrate required to get to Vmax/2)
What happens during non-competitive inhibition?
inhibitor binds at a different site than the substrate. So enzyme can bind substrate, inhibitor, or both
What happens differently in pure non-competitive inhibition?
binding changes the structure of the active site such that substrate still binds, but transition state stabilisation is no longer optimal
What happens to Vmax and Km in pure non-competitive inhibition
Vmax - decreases
Km - stays the same
What happens to Vmax and Km during mixed non-competitive inhibition?
Vmax and Km both change
