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Chymosin Lab
1. Which variables influence enzyme performance in general?
2. With these variables in mind, hypothesize: What are the optimal conditions for the performance of chymosin? (Hint: you might investigate the normal conditions under which substances like chymosin are active).
3. Briefly describe an investigation aimed at optimizing one variable in chymosin Performance.
Milk contains casein
• Casein- German, Kase= cheese
• Casein is an emulsifying protein
• It is also a storage protein
• Structurally similar to gluten (found in grains)
Cheese is made from curdled milk
• Rennet is added from the 4th stomach of a calf
• Rennet contains chymosin
• Chymosin is an enzyme which cuts casein
ENZYMES
• They are protein catalysts
• They speed up reactions inside cells
• They are incredibly specific
• They are incredibly efficient
• -ase = “enzyme”
Chymosin is a protease
• A protease is an enzyme which cuts proteins
• Specifically, it is an aspartate protease
• Has an aspartate residue at its active site
• HIV-Protease 1 is also an aspartate protease
Enzymes make it easier for reactions to happen
Reactions can be exergonic, yet slow- they require activation energy
Lowering the activation energy makes enzyme-catalyzed reactions faster
THE REACTION DIAGRAMEnzymes can dramatically lower the energy of activation for a reaction
Reaction Course
Energyreactants
products
E a
E a
no enzyme
with enzyme
12Note that the equilibrium of the reaction is unaffected
The stages of enzyme catalysis
• Substrate(s) binding• Reaction of substrate to
form product(s)• Release of products• The enzyme is ready to
bind the next substrate• Enzymes are unchanged
by the reactions they catalyze
Enzyme Inhibition- Enzymes can be sped up or slowed down
Protease inhibitors make enticing HIV drug candidates
Effects of Temperature and pH
• Each enzyme has an optimal temperature in which it can function
• Each enzyme has an optimal pH in which it can function
• Tertiary structure can be radically altered by changes in pH
Optimal temperature fortypical human enzyme
Optimal temperature forenzyme of thermophilic (heat-tolerant bacteria)
Temperature (°C)
Optimal temperature for two enzymes
0 20 40 60 80 100
Rate
of r
eacti
onOptimal pH for pepsin(stomach enzyme)
Optimal pHfor trypsin(intestinalenzyme)
pH
Optimal pH for two enzymes
0
Rate
of r
eacti
on
1 2 3 4 5 6 7 8 9 10
Different enzymes work optimally at different pHs and temper-atures
1. Which variables influence enzyme performance in general?
2. With these variables in mind, hypothesize: What are the optimal conditions for the performance of chymosin? (Hint: you might investigate the normal conditions under which substances like chymosin are active).
3. Briefly describe an investigation aimed at optimizing one variable in chymosin Performance.
-galactosidase
10
-galactosidase
11
lactose
galactose
glucose
H2O
- galactosidase(aka lactase in humans)