Choline kinase activity in the developing rat spinal cord: differential development of hemicholinium-3 sensitive and insensitive activity.

Abstract— Choline kinase (ATP:cholinephosphotransferase; EC 2.7.1.32) activity was measured in preparations of lumbar spinal cord from rats ranging in development from 12 days of gestation to 46 days of age. The enzyme activity was measured with a radiochemical assay procedure suitable for whole tissue preparations which are rich in ATP-metabolizing enzymes. Total choline kinase activity was further differentiated into hemicholinium-3 (HC-3) sensitive and HC-3 insensitive components. The specific activity of choline kinase (unhibited) increased 3-fold during the prenatal period and subsequently decreased to relatively low levels by birth. There was no significant change in choline kinase activity throughout the postnatal period. The ontogenetic patterns for the HC-3 sensitive and HC-3 insensitive components of choline kinase activity had transient peaks in activity during the prenatal period; however, these peaks in specific activity for the 2 components were 2–3 days out of phase temporally. HC-3 insensitive activity reached a peak at 18 days of gestation while the HC-3 sensitive activity peaked at 2CL21 days of gestation. In the 10-day-old rat, the apparent choline K_m values were 0.56 and 0.16 MM for the total activity, 0.58 and 0.13 mM for the HC-3 insensitive activity, and 0.47 for the HC-3 sensitive activity.