Deoxyribose 5-phosphate aldolase: an enzyme that peaks in the G2 phase of rat hepatoma cells.

The activity of deoxyribose 5-P aldolase (2-deoxy-d-ribose 5-phosphate acetaldehyde lyase, EC 4.1.2.4) increases three- to fourfold in cultures of rat hepatoma cells that have reached stationary growth and have stopped in the G₂ phase of the cell cycle. We have shown that in cell cultures synchronized by three independent methods the enzyme activity peaks in late G₂, followed by a rapid decline during mitosis. Two compounds, dibutyryl cAMP and isoproterenol, that appear to block these cells in G₂, also cause a two- to fourfold increase in deoxyribose 5-P aldolase activity. It is suggested that this enzyme may play a role in lowering the pools of deoxyribonucleotides in the late $\text{G}{}_2\text{M}$ phase of the cell cycle.