Mechanism of Enzyme Action | Biochemistry for MCAT PDF Download

 Page 1


CHAPTER 11 
Mechanism of Enzyme Action 
1. General properties of enzymes 
2. Activation energy and the  
    reaction coordinate 
3. Catalytic mechanism 
4. Lysozyme 
5. Serine proteases 
Enzyme act with great 
speed and precision 
Page 2


CHAPTER 11 
Mechanism of Enzyme Action 
1. General properties of enzymes 
2. Activation energy and the  
    reaction coordinate 
3. Catalytic mechanism 
4. Lysozyme 
5. Serine proteases 
Enzyme act with great 
speed and precision 
Introduction 
1.? Enormous variety of chemical reactions within a cell 
2.? Mediated by Enzymes 
3.? Enzymology, the study of enzymes  
(coined 1878; Greek: en, in; zyme, yeast),  
fermentation: glucose -> ethanol 
12 enzyme-catalyzed steps 
4.? James Summer, 1926, crystallized urease  
from jack bean, shown to be a protein 
5.? Other catalysts, i.e. ribozymes (peptide-bond 
formation; “RNA-world”), only for units 
6.? Proteins more versatile, 20 functional units 
Page 3


CHAPTER 11 
Mechanism of Enzyme Action 
1. General properties of enzymes 
2. Activation energy and the  
    reaction coordinate 
3. Catalytic mechanism 
4. Lysozyme 
5. Serine proteases 
Enzyme act with great 
speed and precision 
Introduction 
1.? Enormous variety of chemical reactions within a cell 
2.? Mediated by Enzymes 
3.? Enzymology, the study of enzymes  
(coined 1878; Greek: en, in; zyme, yeast),  
fermentation: glucose -> ethanol 
12 enzyme-catalyzed steps 
4.? James Summer, 1926, crystallized urease  
from jack bean, shown to be a protein 
5.? Other catalysts, i.e. ribozymes (peptide-bond 
formation; “RNA-world”), only for units 
6.? Proteins more versatile, 20 functional units 
Introduction 
Enzymes increase the rate of chemical  
reactions by lowering the free energy  
barrier that separates the reactants  
and products 
Page 4


CHAPTER 11 
Mechanism of Enzyme Action 
1. General properties of enzymes 
2. Activation energy and the  
    reaction coordinate 
3. Catalytic mechanism 
4. Lysozyme 
5. Serine proteases 
Enzyme act with great 
speed and precision 
Introduction 
1.? Enormous variety of chemical reactions within a cell 
2.? Mediated by Enzymes 
3.? Enzymology, the study of enzymes  
(coined 1878; Greek: en, in; zyme, yeast),  
fermentation: glucose -> ethanol 
12 enzyme-catalyzed steps 
4.? James Summer, 1926, crystallized urease  
from jack bean, shown to be a protein 
5.? Other catalysts, i.e. ribozymes (peptide-bond 
formation; “RNA-world”), only for units 
6.? Proteins more versatile, 20 functional units 
Introduction 
Enzymes increase the rate of chemical  
reactions by lowering the free energy  
barrier that separates the reactants  
and products 
1. ? General Properties of Enzymes  
Enzymes differ from ordinary chemical  
catalysts by: 
-? Higher reaction rates, 10
6
-10
12 
-? Milder reaction conditions (temp, pH, …) 
-? Greater reaction specificity (no side products) 
-? Capacity for regulation 
Definition catalyst: catalyzes reaction but  
is not itself consumed during the process 
Page 5


CHAPTER 11 
Mechanism of Enzyme Action 
1. General properties of enzymes 
2. Activation energy and the  
    reaction coordinate 
3. Catalytic mechanism 
4. Lysozyme 
5. Serine proteases 
Enzyme act with great 
speed and precision 
Introduction 
1.? Enormous variety of chemical reactions within a cell 
2.? Mediated by Enzymes 
3.? Enzymology, the study of enzymes  
(coined 1878; Greek: en, in; zyme, yeast),  
fermentation: glucose -> ethanol 
12 enzyme-catalyzed steps 
4.? James Summer, 1926, crystallized urease  
from jack bean, shown to be a protein 
5.? Other catalysts, i.e. ribozymes (peptide-bond 
formation; “RNA-world”), only for units 
6.? Proteins more versatile, 20 functional units 
Introduction 
Enzymes increase the rate of chemical  
reactions by lowering the free energy  
barrier that separates the reactants  
and products 
1. ? General Properties of Enzymes  
Enzymes differ from ordinary chemical  
catalysts by: 
-? Higher reaction rates, 10
6
-10
12 
-? Milder reaction conditions (temp, pH, …) 
-? Greater reaction specificity (no side products) 
-? Capacity for regulation 
Definition catalyst: catalyzes reaction but  
is not itself consumed during the process 
Table 11-1