Question

If an enzyme's active site contains only two ionizable residues, an arginine and a glutamate (pKa's of 2.9 and 9.1, respectively) that participate in the catalytic mechanism, what would you expect for the optimum pH of the enzyme?

Answer 1

Answer:

Optimum pH= 6

Optimum pH for the given enzyme would be the average of pKa values of two amino acids (2.9 + 9.1 /2= 6)

Explanation:

The pKa represents the association constant of amino acids. It is calculated by taking the negative log value of the ratio of a dissociated acid and the conjugated base which in turn regulates the isoelectric point (pI) of the protein.

The amino acids present in the active site of the enzyme regulate the interaction of enzyme and substrate. The given enzyme contains two ionizable amino acids with pKa values of 2.9 and 9.1 respectively. Therefore, the optimum pH of the given enzyme would be 2.9 + 9.1 / 2 = 12/2 = 6.  

At pH 6, both the ionizable amino acids would serve as a good buffer with their active proton donor and proton acceptor species.