Abstract
Activities of cholinephosphotransferase (EC 2.7.8.2) and ethanolaminephosphotransferase (EC 2.7.8.1) were evaluated in microsomal preparations derived from rabbit cerebrum. Animals ranged in age from nineteen day's gestation through two months of postnatal development. Under optimal conditions the properties of these transferases in rabbit brain were remarkably similar relative to pH, divalent cation requirements, and apparent‐Km values for the CDP‐intermediates and the lipid acceptor, respectively. Cholinephosphotransferase‐specific activity exhibited a dramatic rise during the last 15%–20% of fetal life and a second rise to a maximum near the 15th postnatal day. Ethanolaminephosphotransferase‐specific activity exhibited a similar, but less striking age‐related increase during the same period. Growth of rabbit cerebrum, as determined by weight, increased 30‐fold during this same period (24 days gestation to the 19th postnatal day). Specific activities of these transferases were similar in brain preparations from mid‐fetal and early adult rabbits. The maximum specific activity of cholinephosphotransferase exceeded that of ethanolaminephosphotransferase by 3–4‐fold.
Age‐related changes in the specific activities of these transferases appear to correlate with the developmental pattern of morphological and compositional events occurring in rabbit cerebrum during the last third of gestation and the first three weeks of postnatal life.