Lecture 16
11/2/11
Assignment:
Segel:
Page 319: problems 2, 6, 7
Background reading:
Berg, et al:
Pages 238 – 240
Garrett and Grisham:
Pages 417 – 419 and 421 - 423
Outline:
•
V
max
and K
M
•
Lineweaver-Burk plot
•
Enzyme inhibition
•
Competitive inhibition

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In the last lecture we derived the Michaelis-Menten equation that describes
the hyperbolic curve we get by plotting initial velocity (v
o
) as a function of [S]:
v
=
V
max
[S]
K
M
+ S
Can use this equation to calculate points
on the curve.
•
V
max
and K
M
When the [S] >> K
M
(Greater than 100 x K
M
):
The K
M
is small and drops out and the equation becomes v = V
max
P
O
Get
Zero order kinetics
in which the rate of reaction is independent
of [S].
When the [S] << K
M
(Less than .01 x K
M
):
v =
V
max
[S]
K
M
= k [S]
Get
First order kinetics
in which the velocity is directly proportional to
the [S] and the line is straight.
If v = ½ the V
max
the
K
M
= [S]
Thus the K
M
is equal to the substrate concentration at which the reaction
rate is half its maximal value.