Question

Q.1) Why is the optimal pH curve for an enzyme symmetrical but the optimal temperature curve for an enzyme is asymmetrical?

Q.2) What is ES‡? What is the difference between ΔG‡ and ΔG?

Answer 1

1.     Certain enzymes function better at lower pH. Enzymes in the stomach have a low optimum pH because they hydrolyze proteins at the acidic pH in the stomach. For example, pepsin, a digestive enzyme in the stomach, has an optimum pH of 1.5 to 2.0. So the optimal pH curves for an enzyme symmetrical.

2.     A superscript ‡ indicates a property of the transition state. ES^‡ is enzyme-transition state complex. ΔG is Gibbs free energy change for a reaction, where ΔG^‡ is the difference between the affinity of the enzyme for the transition state S^‡ and for the substrates.