Differences in pH within the cellular environment are associated with several cellular processes. Examples include the intracellular acidification associated with apoptosis; 2-3 reduced protein glycosylation that results from impaired acidification of the Golgi compartment; 4 the pHdependent regulation of synaptic activity in neurons. Intracellular pH varies by from 0.3 to 0.5 units during the process of mitosis. Intracellular pH has a large role in the activity of many proteins, including enzymes that exhibit pH dependencies on catalysis, providing clear connections with the associations between pH and cellular processes. Mutations can affect an enzyme's pH dependency in several ways, and the potential effects of disease-associated mutations could arise from the resulting dysregulation of key enzymes in the cell.