If the PH and temperature changed significantly beyond the enzyme optimum level it will become denatured and then the enzyme would not work.
The Enzyme is a biological catalyst which speeds up a reaction. The Enzyme has molecules which act upon as substrates and then it converts those substrates into different molecules which are called products.
The study of the enzyme is known as enzymology, and they are well known to catalyze more than 5,000 biochemical reaction types.