Fatty Acid Synthesis by Isolated Chromoplasts from the Daffodil [14C]Acetate Incorporation and Distribution of Labelled Acids

Abstract

Isolated daffodil (Narcissus pseudonarcissus) chromoplasts showed high rates of [14C]acetate incorporation into lipids. The fatty acids synthesized were predominantly palmitic acid (93%). The radioactivity incorporated was shared mainly between long-chain acyl-CoA (25%), free fatty acids (24%), phosphatidic acid (17%), diacylglycerol (15%), and phosphatidycholine (11%). Galactolipids were not labelled. ATP, NaHCO3, and also the structural integrity of the organelles were essential. Omission of exogenous CoA led to a decreased incorporation (49%); under these conditions the label was distributed mainly between free fatty acids (66%) and diacylglycerol (19%). Addition of lysophosphatidylcholine increased the labelling of phosphatidylcholine, whereas addition of glycerol 1-phosphate increased the labelling of phosphatidic acid and diacylglycerol. Acyl-CoA synthetase and acyl thioesterase (acyl-Coa) activities could be demonstrated. The results are discussed in terms of chromoplasts as non-photosynthetic organelles exhibiting high lipid-synthesizing capabilities.