Question

Enzyme X exhibits maximum activity at pH = 5.25. X shows a sharp decrease in its activity when the pH goes much lower than 4.35. One likely interpretation of this pH activity is that:

A) a Glu residue (pKa = 4.25) on the enzyme is involved in the reaction.

B) a His residue (pKa = 6.0) on the enzyme is involved in the reaction.

C) the enzyme has a metallic cofactor.

D) the enzyme is found in gastric secretions.

E) the reaction relies on specific acid-base catalysis.

Answer 1

ANSWER:

Given;

As the enzymatic activity decrease as the pH decreases that means the medium turns basic to acidic. and the enzyme shows activity at basic pH so the responsible amino acid will be histidine which has imidazole ring and is basic in nature. and the basic amino acid will show higher activity at higher pH so it is the reason why the activity decreases. it can't be in gastric secretion because in stomach pH is 1-1.2.

Thankyou!