Cholinephosphotransferase activity during development of the sea urchin, Arbacia punctulata

Cholinephosphotransferase activity was examined during early development of Arbacia punctulata embryos. CMP was rapidly incorporated by enzyme preparation from Arbacia embryos into a compound identified as CDP-choline. Activity was dependent upon the presence of Mg²⁺, Mn²⁺, or Co²⁺, and was maximal in phosphate buffer, pH 7.0, containing 3 × 10^?2M MgCl₂ and 2 × 10^?5M CMP. Addition of ATP or egg lecithin had no effect on enzyme activity. The activity was localized in the 1000 g and 10,000 g pellets, with little or no activity in the microsomal fraction.Upon fertilization, cholinephosphotransferase activity decreased rapidly, detectable changes in activity being observed within 2 min after fertilization. After reaching a minimum activity 2 hr after fertilization, the enzyme activity increased up to the gastrula stage, then decreased once more. Possible interference by competing enzymes was examined and found to be negligible.