Enzymes Flashcards
What is an inhibitor?
A molecule that binds to an enzyme and reduces its catalytic activity
What are the two major classes of inhibitors?
- Reversible (inhibitor can dissociate from enzyme)
2. Irreversible (inhibitor cannot dissociate from enzyme; covalent bonds)
What are the 3 sub-classes of reversible inhibitors?
- Competitive
- Non-competitive
- Un-competitive
What fractional amount of therapeutic drugs are inhibitors?
1/4 (25%)
What is a non-competitive inhibitor?
“No competition.” The inhibitor can bind the free “E” or the “ES” complex. Usually binds to an allosteric site.
What is an un-competitive inhibitor?
An inhibitor that only binds to the “ES” complex.
What type of inhibitor are suicide substrates?
Suicide substrates are a type of irreversible inhibitor.
What can protect an enzyme from suicide substrates?
High concentrations of regular substrate. (Temporary effect)
What do suicide substrates do?
Suicide substrates look like substrate, but covalently attach to the enzyme active site during catalysis.
What does the “catalytic speed” of an enzyme refer to?
The rate at which an enzyme can convert substrate to product.
An enzyme____the transition state, which _____the activation energy needed for the reaction to proceed.
stabilizes, decreases
What is the function of a protease?
A protease modifies a protein by cutting a peptide bond. This can either activate or inactivate the protein.
_____ proteases are used primarily used in clotting cascades.
Serine
What is the function of “Serpin” proteins?
Serpin proteins are suicide substrates that inactivate serine proteases.
What is Antithrombin III?
An important “Serpin” that inhibits Thrombin function leading to less clotting.
