1. Exploring Enzymes: Lactex Lab

2. Your Task:
You are a scientist at a company called Pharmex. Recently a new treatment for lactose intolerance, Lactex®, has been developed. In order to verify the activity of Lactex®, the enzyme must be tested on different milks which contain sugars, to verify that it only works on lactose. If the enzyme has additional activities on other sugars, it may not be approved for use by the FDA. Four samples, each containing a different sugar, will be tested with Lactex. Your job is to determine if Lactex® is specific for the sugar lactose.

3. Test Solutions:
Cow’s Milk: Lactose = Glucose-Galactose
Soy Milk: Sucrose = Glucose-Fructose
Maltose = Glucose-Glucose
Rice Milk: Glucose
Water

4. What are Enzymes?
Proteins that catalyze (speed up) a biochemical reaction
Lower the amount of energy needed to start a reaction
Do not get used up as part of the reaction
Identified by their ‘ase’ Ending
Enzymes act upon substrates
Animation

5. Lactase
The sugar lactose is the substrate for the lactase enzyme: Given that other sugars have similar chemical structures, is lactose the only substrate for this enzyme???

6. Lactose Intolerance
Lack sufficient lactase enzyme  Inability to digest lactose
What causes lactose intolerance?
Genetics
Age
Certain medications, infection

7. Lactose Intolerance by Region
Most mammals normally become lactose intolerant after weaning. Some human populations have developed lactase persistence (in which lactase production continues into adulthood) resulting from a mutation that is postulated to have occurred 5,000-10,000 years ago, coinciding with the rise of cattle domestication. This mutation has allowed almost half of the world’s population to metabolize lactose without symptoms. This distribution is now thought to have been caused by recent natural selection favoring lactase persistent individuals in cultures that rely on on dairy products. (Source: Wikipedia)

8. Materials Cow’s milk - contains lactose Soy milk - contains sucrose
Rice milk - contains glucose
Maltose
Distilled Water
Lactex Enzyme Solution – contains lactase enzyme
Glucose test strips

9. Glucose Test Strips
Read results at 30 Seconds. Record in % or mg/dL.

10. Data Table Solution Before Enzyme After Enzyme Glucose Presence:
Prediction / Actual
After Enzyme
Cow Milk (lactose) /
Soy Milk (sucrose)
Rice Milk (glucose)
Maltose (optional)
Distilled Water
Discussion - What do you think will happen?

11. C S R W Procedure Step 1: Test for Glucose:
Cow Milk
(lactose)
Soy Milk
(sucrose)
Rice Milk
(glucose)
Water
Step 1: Test for Glucose:
Record Results in Data Table

12. Glucose Test Strips
Read results at 30 Seconds. Record in mg/dL.

13. Procedure C S R W
Cow Milk
(lactose)
Soy Milk
(sucrose)
Rice Milk
(glucose)
Water
Lactex
Step 2: Add 0.5 ml lactase enzyme to each solution – swirl and wait 2 minutes

14. C S R W Procedure Step 3: Test for Glucose again.
Cow Milk
(lactose)
Soy Milk
(sucrose)
Rice Milk
(glucose)
Water
Step 3: Test for Glucose again.
Record Results in Data Table

15. Glucose Test Strips
Read results at 30 Seconds. Record in mg/dL.

16. Conclusion
Discuss your results with your lab partner, then as a class. Is the lactase enzyme specific for the sugar lactose? What evidence do you have to support this conclusion?

17. Conclusion Is the lactase enzyme specific for the sugar lactose?
Enzymes are specific for a given substrate.
Lactose is specific for the lactase sugar.
If your results do not support this conclusion, why might this be?

18. Next Steps
How does the lactase enzyme function under different conditions? pH
temperature