Deoxyribonuclease II in apoptosis and the significance of intracellular acidification.

Many endonucleases have been identified in cells, but which are involved in apoptosis remains controversial. We detected and characterized an endonuclease as deoxyribonuclease II. Its most important characteristic is its acidic pH optimum that requires decreased intracellular pH for activation. Intracellular acidification has been observed during apoptosis in a number of systems. This acidification results from a selective loss of pH regulation, and is likely due to dephosphorylation of proton exchangers. The fact that growth factors normally prevent apoptosis and also phosphorylate ion exchangers suggests the critical role of intracellular kinase cascades for preventing apoptosis.