At what ph could you assume the enzyme catalase was denatured?

This is different for different enzyme catalase.
This is because each type of enzymes has their own optimum pH, the pH value where they work best at.
When the pH value gets extremely lower or higher than the optimum pH, the enzyme would be denatured.
For example, the enzyme Pepsin in human stomach works best at around pH 2.0, so we may assume when pH 5 it would be completely denatured.
Or for example, salivary amylase has an optimum pH of 7, so it may be denatured in around pH 10