Activity and some properties of choline kinase, cholinephosphate cytidyltransferase and choline phosphotransferase during liver development in the rat

Abstract

The activity of choline kinase (ATP:choline phosphotransferase, EC 2.7.1.32) cholinephosphate cytidyltransferase (CTP:cholinephosphate cytidyltransferase, EC 2.7.7.15) and cholinephosphotransferase (CDP-choline:1,2-diacylglycerolcholine-phosphotransferase, EC 2.7.8.2) was determined during the development of the liver in the rat. Choline kinase activity was located in the 100000 x g supernatant and is slightly lower than adult in -- 5 day fetal liver. The activity increases to almost 2 times the adult prior to birth and declines to adult levels shortly after birth. The cholinephosphate cytidyltransferase is found at all ages in both the 100000 x g supernatant and in microsomes. The distribution of activity between these two fractions varies with the age of the animal. The activity in the supernatant fraction from -- 5 day fetal is almost twice the adult values, whereas the activity in the microsome fraction from -- 5 day fetal does not significantly differ from the adult. The activity in both fractions increases following birth. The activity of cholinephosphotransferase in the presence of exogenous diglyceride was about 10% of the adult values in -- 5 day fetal liver. The activity increased slightly prior to birth but did not approach the adult levels until 8 days after birth. The addition of diglyceride to the assays did not increase the enzyme activity from fetal liver but caused a 2-3-fold increase in enzyme activity from 5 day and older animals. The developmental activities of the three enzymes are compared to the previously obtained developmental pattern for the incorporation of [Me-14C]-choline into choline phosphoglycerides by liver slices.