1. ENZYME INHIBITION

2. Review: How do we characterize enzyme functions?
The rate of an enzymatic reaction depends on the concentration of substrate.
Product
Time S4 S3 S2 S1
Increasing substrate
concentration
The Michaelis-Menten equation relates the initial velocity of the reaction
to the concentration of substrate. V
V = Vmax [S]/([S]+Km)
[S]

3. Review: How do we characterize enzyme functions?
The Lineweaver-Burke and Eadie-Hofstee equations transform the
Michaelis-Menten data to more accurately estimate Km and Vmax.
1/V
1/V = (Km/Vmax)(1/[S]) + 1/ Vmax
1/[S] V
V/[S]

7. 1/V
-1/Km
- 1/Km, apparent
1/[S]

8. -I V +I
[S]

10. -I +I
1/V
1/[S]
1/Vmax
1/Vmax,apparent

11. -I V +I
[S]

12. +I -I
1/Vmax
1/[S]
1/Vmax, apparent
-1/Km
-1/Km,apparent
1/V

13. Summary
Enzyme activity can be inhibited by compounds that interact
with the enzyme’s active site (or with other sites that change
the enzyme’s structure).
Competitive inhibitors bind to the active site and compete
with substrate.
Non-competitive inhibitors bind to a separate site and
Inactivate the active site.
Uncompetitive inhibitors bind to an enzyme-substrate complex.
The type of competition and the enzyme-inhibitor binding
affinity can be determined from Michaelis-Menten kinetic
experiments.