Amino Acids

Dr. Anderson is studying the activity of the enzyme stressase. The enzyme has been shown to be very active in biochem students who are taking an exam. The active site of the protein utilizes the protonated functional group of glutamic acid. The pKas of glutamic acid are: Carboxylate: 2.10, R-Group: 4.07, and Amino: 9.47.

a. Assuming this glutamic acid is not the N- or C- terminus of the protein and the active site is on the surface of the protein what pH ranges would he see virtually no activity? Briefly justify.

b. At what pH would the ration of protonated to deprotonated concentrations of glutamic acid R-group be equal to 3.45?