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Abstract
The Ca 2+ dependent incorporation of [ 14C]ethanolamine, l-[ 14C]serine and [ 14C]choline into phosphatidyl-ethanolamine, phosphatidylserine and phosphatidylcholine, respectively, were investigated in membrane preparations from rat heart. The ethanolamine and serine base-exchange enzyme-catalyzed reactions were associated with the sarcolemma and sarcoplasmic reticulum. There was a 17.2-fold and 6.8-fold enrichment, respectively, of the serine and the ethanolamine base-exchange enzyme activities in the sarcolemma compared to the starting whole homogenate. The sarcoplasmic reticulum was enriched in the ethanolamine and serine base-exchange enzyme activities. The choline base-exchange enzyme activity of all membranes fractions was negligible compared to the ethanolamine or serine base-exchange enzyme activities. The apparent K m for the ethanolamine and serine base-exchange enzyme in sarcolemma was 14 μM and 25 μM. respectively. The pH optimum for these base-exchange activities was 7.5–8.0. There was a dependence upon Ca 2+ for these reactions with a 1 or 4 mM concentration required for maximal activity. The properties of the sarcoplasmic reticulum base-exchange enzymes were similar to the sarcolemmal base-exchange enzymes.
Published Version
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Schedule a callMore From: Biochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism
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