Answer:
Generally, most enzymes work best at the neutral pH of 7.The specificity of their functions is determine by the 3-Dimensional shape of their active sites, and this is sensitive to low or high pH of the cells Enzymes are examples of globular proteins with R-groups. These R-groups could have positive or negative in charges,this refers to their ionization.
When the pH of a cell is very low in the containing organ, the hydrogen ion concentration of the medium is high( since pH is negative log of hydrogen ion concentration,) The high hydrogen ion reacts by interacting with the R-group of the enzyme altering their ionization, which weakened the ionic bonds holding the 3-D structure of the enzyme molecules in shape.
The loss of 3-D arrangement disrupts the active site ,and therefore denatures the globular protein structure of enzyme. This result to failure of the enzyme to from needed enzyme-substrate-complex of enzymatic reaction.Therefore the enzyme is no longer specific, thus function is lost.
Conversely, at a very high pH of the cells, the ionization of the R-group is also affected,and the enzymes specificity of action affected. However effective buffer system always prevented these functions in pH from taken place..