Journal of Lipid Research, Vol 34, 125-137, Copyright © 1993 by Lipid Research, Inc.
Metabolism of molecular species of phosphatidylethanolamine and phosphatidylcholine in rat hepatocytes during prolonged inhibition of phosphatidylethanolamine N-methyltransferase
RW Samborski, ND Ridgway and DE Vance
Lipid and Lipoprotein Research Group, University of Alberta, Edmonton, Canada.
The metabolism of the molecular species of phosphatidylethanolamine (PE)
and phosphatidylcholine (PC) derived from [3H]ethanolamine has been studied
in rat hepatocytes during prolonged inhibition of
phosphatidylethanolamine-N-methyltransferase (PEMT) with 3- deazaadenosine
(DZA). After an initial pulse of radioactivity for 1 h and a chase for up
to 24 h in the presence or absence of DZA, the cells were harvested and the
incorporation of label into the various molecular species of PE and PC was
determined. Prolonged inhibition of PEMT did not affect the mol%
distribution of either PE or PC molecular species. Thus, PE methylation is
not required for the maintenance of cellular PE and PC molecular species
composition. While the overall catabolism of PE was not affected by DZA
treatment, inhibition of PEMT resulted in the selective degradation of
16:0-22:6-PE. The major catabolic products of PE in the hepatocytes and the
medium were glycerophosphoethanolamine and ethanolamine-phosphate. PC,
derived from PE, was remodeled at both the sn-1 and sn-2 positions and this
process was not affected by the inhibition of PEMT. The major species being
remodeled was 16:0-22:6-PC. The rapid turnover of 16:0-22:6-PE and PC
species compared to other PE and PC species may be due to the presence of a
16:0-22:6 selective phospholipase.
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