Myoglobin vs' Hemoglobin

1
18
Myoglobin vs. Hemoglobin
single polypeptide a2b2
muscle RBCs
binds O2 (P50 1) binds O2 (P50 26)
storage/local transport transport
simple binding allosteric - regulation
2
20
Mb
1
Bisphosphoglycerate (BPG) is allosteric
regulator of Hb
0.5
Hb
0
100
20
40
PO2
torr
3
1
Enzyme Regulation determines Relative Product
amounts.
S
4
Metabolic Regulation
2
1. How Much Enzyme
Regulation of Gene Expression
2. Activity of Available Enzyme
Allosteric Enzymes
Covalent Modifications
Proenzymes
5
3
inactive form
active form
Any molecule that selectively binds one from
will stabilize that form.
6
4
7
negative effector
5
only binds inactive form
8
6
negative effectors displace curve to right.
v
S
9
positive effector
7
inactive form
active form
only binds active form
10
8
v
S
11
9
Glucose
Allosteric Feedback is usually just good common
sense
12
Covalent Modification
10
Enzyme has active inactive forms
Transformation due to phosphorylation of Side
Chain
Protein Kinase catalyzes Phosphoryl transfer
(ATP donor)
Phosphatase reverses
13
11
All or None
14
PROENZYMES
12
15
13
16
14
17
TRYPSINOGEN ACTIVATION
15

• Trypsinogen from Pancreas
• Enterokinase from Intestinal Cells
• Both are secreted into intestines.
• Trypsinogen ? Trypsin.
• Digestion doesnt occur in Pancreas!!

18
16
Enzyme Regulation
Allosteric incremental rev /-
effectors Covalent all or none rev
Kinase/ Modification Phosphatase Proenzy
mes all or none irrev. Protease