The pKa of an acid depends partly on its environment. Predict the effect of each of the following environmental changes on the pKa of a glutamic acid side chain. (a) A lysine side chain is brought into proximity. (b) The terminal carboxyl group of the protein is brought into close proximity.

A. Decrease

B. Increase

Explanation:

A. A lysine side chain is brought into proximity:

lysine is basic in its nature, it would have to stabilize the electrostatic interaction and also weak interactions existing among the acidic amino acids and hydrogen bond. This would then reduce or decrease the pH and thus pKa of the protein.

B. The effect of this on pKA is an increase on the pKA. The carboxyl group is acidic. When it is removed, it would then cause the pKA to be increased. There would be accumulation of more negative change by basic amino acids increasing the pKA.