The effect of embryological development on phosphatidylethanolamine methyltransferase, phosphatidyldimethylethanolamine methyltransferase and choline phosphotransferase of rabbit liver microsomes.

The effect of embryological development on the two biosynthetic enzymes involved in phosphatidylcholine biosynthesis in liver microsomes of -12, -9, 0, +4, +14, +36 day old rabbits has been determined. The specific activity (pmol phosphatidylcholine formed/min/mg microsomal protein) of the phosphatidylethanolamine methyltransferase in the liver microsomes is very low before birth and a 33% increase at birth occurs when compared to the -12 day old fetal livers. The pmol of phosphatidylcholine formed/min/mg protein by the choline phosphotransferase pathway in fetal liver microsomes is 5, 10, 73, 199, 107 and 307 times greater than by the phosphatidylethanolamine methyltransferase pathway for -12, -9, 0, +4, +14, +36 day old rabbits, respectively. The specific activities of the choline phosphotransferase in the liver microsomes increased from the -12 day old fetal livers to 1.6, 19, 73, 39, 27 times for the -9, 0, +4, +14 and +36 day old animals, respectively. The choline phosphotransferase pathway in comparison to the phosphatidylethanolamine methyltransferase pathway is providing the major phosphatidylcholines in the membranes of the endoplasmic reticulum before birth and early fetal development of the rabbit.