Enzyme Kinetics II: Inhibitors Flashcards
Fill in the blank:
What do competitive inhibitors do? And how? (Enzymes)
Do: reduce activity of an enzyme.
How: 1. Affects substrate binding 2. Affects conversion from S to P.
Why is a smaller Ki the better inhibitor?
Smaller Ki means EI has a much higher concentration equilibrium relative to E + I
How does competitive inhibition affect the Michaelis-Menten equation? Lineweaver-Burk equation?
Vmax= unchanged: v-max describes the behavior at infinite levels of substrate. A competitive inhibitor can’t out compete with infinite.
Km= increased by factor alpha.
M-M equation: make slope less steep.
Lineweaver eq: makes slope more steep. NOT the y-intercept!
Define uncompetitive inhibition.
Inhibitor binds to the enzyme substrate complex, not to the free enzyme.
How does uncompetitive inhibition affect Michaelis-Menten’s equation? Lineweaver-Burk’s?
Effects Vmax: even at high levels of substrate since it isn’t competing with the substrate, it will still affect it regardless of how much there is. reduced by a factor of alpha prime
Effects Km: reduced by a factor of alpha prime too.
Test: do you know these equations?
No answer, just check in.
Uncompetitive inhibition reduces KM by alpha prime, why doesn’t this mean uncompetitive inhibition makes the rate more effective?
Because alpha prime also reduces Vmax, meaning less substrate is needed to get half of Vmax as well.
Competitive inhibition does best when substrate is at low concentrations, is this the same for uncompetitive inhibition?
No uncompetitive inhibition does best at high concentrations of substrate because there is more enzyme substrate complexes.
Define Mixed (noncompetitive) inhibition.
Inhibitor binds to both the enzyme substrate complex and the free enzyme.
How does mixed inhibition affect the slope and intercept in a Lineweaver-Burks plot?
What do the x and y intercepts tell you from the Lineweaver-burka equation for each type of inhibition/no inhibition?
Look back at slide and make it when you have time.
