August 3, 2005

1
Lecture 2

• August 3, 2005
• Lehninger (4th Edition), Chapter 6,

2
ENZYME KINETICS
LNC Chapter 6
3
k First order
reactions A ? P

k Second order reactions A B ?
P A A ? P
4
1st order lnA lnAo - kt or A
Ao exp(-kt)
2nd order 1/A 1/Ao kt
5
TRANSITION STATE THEORY
A catalyst serves in at least two ways it binds
and aligns the substrates it facilitates the
redistribution of electrons (charges)
6
CHAPTER 6 Enzymes and Enzyme Kinetics
k1 k2 E S
ES Products k-1
7
Fig. 6-2
8
Fig. 6-3
9
Derivation of Michaelis-Mentenequation

• 1. equilibrium assumption k-1 gtgt k2
• 2. steady state assumption dES/dt 0
• Note E Etotal ES

10
Hmmm..??
11
k2 x ET x S v
------------------------- Km
S
when S gtgt Km then v ? vmax
and vmax k 2 E T
12
k -1 k 2 Km
k 1
13
d
Km Kd when k -1 gtgt k 2
14
Fig. 6-11
15
Fig. 6-12
16
1 Km 1 1
x vo v
max S v max
y ax b
17
Lineweaver-Burk Plot
Double Reciprocal Plot
box. 6-1
18
- another definition

v max k2 k cat
------------ E T
TURNOVER NUMBER
19
(No Transcript)
20
molecules of substrate / molecule of enzyme /
second moles of substrate / mole of enzyme /
second
21
Reactions with more than one substrate (more
typical)
Overall reaction S1 S2
P1 P2
22
Fig. 6-13
23
Lines intersect ternary complex is formed in the
reaction
LNC 6-14 a
24
This case is also referred to as the
Ping-Pong or double displacement mechanism
LNC 6-13 b
25
Lines do not intersect no ternary complex is
formed
LNC 6-14 b
26
Enzyme Inhibitors
27
Fig. 6-15a
28
Competitive Inhibition
a 1 I / KI
box. 6-2.1
29
Fig. 6-15b
30
Uncompetitive Inhibition
a 1 I / KI
box. 6-2.2
31
Fig. 6-15c
32
Mixed Inhibition
box 6-2.3
When a a, then we also speak of
noncompetitive inhibition
33
FEEDBACK INHIBITION
LNC 6-28
34
LNC 6-26
35
ASPARTATE TRANSCARBAMYLASE
LNC 6-27
36
LNC 6-29a
37
LNC 6-29b
38
LNC 6-29c
39
Part III Bioenergetics and Metabolism Chapter
13 in LNC
40
THE CARBON CYCLE
41
THE NITROGEN CYCLE
42
(No Transcript)
43
(No Transcript)
44
Types of Organic Reactions 1) Group
transfer Glucose ATP
Glu-6-P ADP H2O ATP
Pi ADP 2)
Oxidation-reduction reactions Ethanol NAH
acetaldehyde NADH H 3)
Eliminations, isomerizations, rearrangements aldos
e ketose 4)
reactions involving making or breaking of C-C
bonds Fru-1,6, bisphosphate
dihydroxyacetone-phosphate
glyceraldehyde-3phosphate
45

• End of Lecture 2
• Aug. 3, 2005