Reactions were stopped by the addition of 1 ml of chloroform:
methanol: heptane (1.25:1.41:1, v/v/v), 15.5 ml of 0.2 M NaOH,
150 mM NaCl. The mixture was vortexed and centrifuged for 5 min
at 10,000g. A 0.1 ml aliquot of the methanol-water upper phase,
was removed and subjected to liquid scintillation counting. The
activity was calculated from kinetic measurements based on at
least 5 values collected over 3 h of incubation.