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Lecture 1
• August 1, 2005
• Lehninger (4th Edition), Chapter 3, 4, 6
Figure 4.2b
Figure 4.4a,b
Figure 4.4c
Figure 4.4d
Box 4-1
Figure 4.7a
Figure 4.7b
Figure 4.16sperm whale myoglobin
hydrophobic side chains in blue
space filling model with atoms represented as spheres with van der Waals radii
Figure 4.23a deoxy-hemoglobin
Figure 4.24b
Chapter 6
ENZYMES
Enzymes are catalysts: speed up the reaction
Enzymes have exquisite specificity:
a) selection of substrates (chemical nature, stereochemistry)
b) nature of the reaction catalyzed
Enzyme activity can be regulated
Apoenzyme
+
Co-enzymeCo-factorProsthetic groupMetal ion(s)
Active enzyme
The enzyme chymotrypsin with its active site and its substrate (red)
LNC 6-1
LNC 6-4
Dihydrofolate reductase with the substrates tetrahydrofolate (yellow)and NADP + (red)
EC3.4.17.1: hydrolase - peptidase (subclass) - metallocarboxypeptidase (sub-subclass) -
arbitrary assigned serial number
NOMENCLATURE
Regulation of enzyme activity
1. At the level of gene expression and protein turnover
2. By covalent modifications of side chains
3. By binding of small molecules (ligands) that are not substrates
4.
allosteric mechanisms in multisubunit enzymes
ENZYME KINETICS
LNC Chapter 6
REACTANTS
SUBSTRATESPRODUCTS
kFirst order reactions: A P
kSecond order reactions: A + B P
1st order: ln[A] = ln[Ao] - kt or [A] = [Ao] exp(-kt)
2nd order: 1/[A] = 1/[Ao] + kt
TRANSITION STATE THEORY
A C
B D
A C
B D
A C
B D
A catalyst serves in at least two ways:it binds and aligns the substratesit facilitates the redistribution of electrons (charges)
• End of Lecture 1
• August 1, 2005
