An enzyme's active site contains an arginine residue and a glutamate residue with pKa's of 2.9 and 9.1,respectively.Both residues are actively involved in the catalytic mechanism and they are the only two ionizable residues in the active site.What would you expect for the optimum pH of the enzyme?
A)4.0
B)6.0
C)8.0
D)No pH can be determined since the information is irrelevant to the optimum pH.

Question

Quizplus · Accepted Answer

The optimum pH for an enzyme is typically near the pKa values of its ionizable side chains when those side chains are involved in catalysis. In this case, with pKa values of 2.9 and 9.1, the optimum pH would likely be between these two values, making 6.0 a reasonable estimate. This pH allows both residues to be in a state conducive to catalysis, with the arginine residue being positively charged (below its pKa) and the glutamate residue being negatively charged (above its pKa).

An Enzyme's Active Site Contains an Arginine Residue and a Glutamate