Assignment 5

In the previous assignment, you learned about the effect of acarbose and DRI inhibitor B on invertase activity. A third inhibitor, l-arabinose, also inhibits invertase. Your goal is to work together in a group to determine the mechanism by which l-arabinose inhibits invertase. Work together in a group of four students to complete the exercises listed in Assignment 5. Please reference and complete Assignment 5 and answer the questions below. Once each pair of students has evaluated their data, discuss and answer the following questions:


1 .		What is the K_I for l-arabinose? Was K_M affected by l-arabinose? Was V_max affected by l-arabinose? What do the plots of apparent K_M and apparent V_maxtell you about what type of inhibitor l-arabinose is?

2 .		Compare the inhibition of invertase by l-arabinose with the results obtained from inhibiting invertase with acarbose and with DRI inhibitor. Were the results similar or different? How were these results similar? How did these results differ? Explain your answers by describing what happened to V_max and K_M in the presence of l-arabinose.

3 .		Based on your results and your knowledge of enzyme inhibitors, does l-arabinose appear to be acting as a competitive inhibitor, noncompetitive inhibitor, or by another mechanism? Consult a biochemistry text for more details if necessary. Once you have a theory on how l-arabinose is working to inhibit invertase, describe your theory and explain how your theory is supported by your data. Design and run additional experiments if necessary until you have generated sufficient data to propose a theory for how invertase is inhibited by l-arabinose. Discuss your experiments and results with your instructor to help you answer this question.