4.3 Enzyme Inhibitors Flashcards
What are enzymes activated by
Cofactors
What are enzymes inactivated by
Inhibitors
What are inhibitors
Molecules that prevent enzymes from carrying out their normal function of catalysis
What are the two types of inhibition
Competitive and non-competitive
How does competitive inhibition work
A molecule that has similar shape to a substrate will be able to fit into the active site of the enzyme
This blocks the enzyme from entering the active site and therefore enzyme cannot carry out its action of catalysis
Why are they called competitive inhibitors
The inhibitor and substrate will compete with each other to fit into the active sites available
Are competing inhibitors affects reversible
Most are
they only bind temporarily to the active site
How does a competitive inhibition affect the rate of reaction
Reduced ror for a given concentration of substrate
doesn’t change the Vmax of teh enzyme it inhibits
Examples of competitive inhibitors
Statins used in synthesis of cholesterol
Aspirin irreversibly inhibits the active site of COX enzymes preventing the synthesis is chemical responsible for pain and fever
How do non-competing inhibitors work
The inhibitor bonds to the allosteric site of the enzyme not the active site
Binding of inhibitor causes tertiary structure of enzyme to change
Active site no longer has complementary shape to substrate
How do non-competing inhibitors affect rates of reactions
Increasing conc of enzyme or substrate will not overcome non-competing inhibitors
Examples of irreversible non-competing inhibitors
Organophosphates used as insecticides irreversibly inhibit the enzyme acetyl cholineestetane
This can lead to cramps paralysis and even death
What are proton pump inhibitors
Used to treat long term indigestion
Irreversibly block an enzyme system responsible for secreting hydrogen ions into the stomach
What is end product inhibition
Product of a reactions acts as an inhibitor to the enzyme that produced it
Serves as negative feedback
Non-competitive reversible inhibition
How does atp go though end product inhibtion
Glucose adds to 2 phosphate groups
Teh 2nd phosphate group added is catalysed by the breakdown of phosphofructokinase and this enzyme is competitively inhibited by ATP
