Enzymes 2 Flashcards
(24 cards)
Michalis Menten Plot
Just be aware of vague shape so you can image/identify it
Pre-Steady State
The study of the few microseconds after the moment an enzyme is mixed with substrate and no product or intermediates have been formed where product formation is unsteady
Steady State
When the rate of formation and breakdown of the intermediate are equal
V0
Initial Rate of reaction
Km
Michaelis Constant - The Concentration of the substrate at half Vmax
Vmax
Speed of enzyme reaction at infinite substrate concentration (Maximum enzyme rate)
How to increase Vmax
Increase the amount of enzyme
Interpret Km
Low - High Substrate Affinity
High - Low Substrate Affinity
**THINK LOGICALLY - IF AN ENZYME HAD HIGH SUBSTRATE AFFINITY, ITS KM WOULD BE LOW BECAUSE IT WOULD TAKE NOT MUCH SUBSTRATE FOR HALF Vmax TO BE REACHED
Describe the order of enzyme reactions relative to a change substrate concentrations when substrate concentration is high vs when it is low
When [substrate] high, it is a 0 order reaction
When low it is a first order reaction
S0.5
Equivalent of Km for multisubunit enzymes as they do not follow the michaelis menton equation/hyperbolic shape
Isozymes
Different forms of an enzyme that catalyse the same thing - they often differ in their Km values based on the role of the enzyme
**Think of function, hexokinase has low Km that will permit even a little glucose to enter glycolysis, while glucokinase is involved in storage so has a higher Km (worse substrate affinity)
Effects of a competitive inhibitor on Vmax
No Effect
Effects of a competitive inhibitor on Km
Km increases as enzyme affinity is reduced
Effect of a non-competitive inhibitor on Vmax
Lowers Vmax as it lowers the concentration of the enzyme
Effect of a non-competitive inhibitor on Km
Not affected as the functional enzymes do not have their affinity affected
Uncompetitive Inhibition
When an inhibitor binds to an enzyme-substrate complex and prevents catalysis
Dead-end complex
[ESI] Complex made by an uncompetitive inhibitor
**E = Enzyme, S = Substrate, I = Inhibitor
When can a substrate of an enzyme act as its inhibitor
At very high substrate concentrations
Describe a lineweaver burke plot
Vague awareness
Just know Vmax and Km
Why might a linweaver burke plot have a hockey stick shape
Due to the substrate acting as an uncompetitive inhibitor by binding to a second non-catalytic site
Why is non-competitive inhibition irreversible
They form covalent bonds with the enzyme and inhibit its function
Examples of two irreversible inhibitors
- Lead
- Carbon Monoxide
- Penicillin
Suicide Inhibitor
Inhibitor that only becomes such when an enzyme acts on it via its active site
Used in drug design
Describe a lineweaver burke plot
Vague awareness
Just know Vmax and Km
