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)