Can someone please help me with this question I know this mu

Can someone please help me with this question? I know this much:

But can someone tell me how they got a pH of 6.5 and why the rate would decrease when the pH is raised?

1. Activity profile. A histidine residue in the active site of aspar- tate transcarbamoylase is thought to be important in stabilizing the transition state of the bound substrates. Predict the pH de pendence of the catalytic rate, assuming that this interaction is essential and dominates the pH-activity profile of the enzyme.

Solution

They got a pH of 6.5; because this must be the PH of the buffer, that is used to measure enzyme activity. The rate would decrease when the pH is raised as the enzyme will get denatured lose its structure as the pH will be raised and hence the enzyme will lose its activity.