Fat Metabolism in Higher Plants XXXVI: Long Chain Fatty Acid Synthesis in Germinating Peas.

A low lipid, high starch containing tissue, namely cotyledons of germinating pea seedlings was examined for its capacity to synthesize fatty acid. Intact tissue slices readily incorporate acetate-(14)C into fatty acids from C(16) to C(24). Although crude homogenates synthesize primarily 16:0 and 18:0 from malonyl CoA, subsequent fractionation into a 10,000g pellet, a 10(5)g pellet and supernatant (soluble synthetase) revealed that the 10(5)g pellet readily synthesizes C(16) to C(28) fatty acids whereas the 10,000g and the supernatant synthesize primarily C(16) and C(18). All systems require acyl carrier protein (ACP), TPNH, DPNH if malonyl CoA is the substrate and ACP, Mg(2+), CO(2), ATP, TPNH, and DPNH if acetyl CoA is the substrate. The cotyledons of germinating pea seedlings appear to have a soluble synthetase and 10,000g particles for the synthesis of C(16) and C(18) fatty acid, and 10(5)g particles which specifically synthesize the very long chain fatty acid from malonyl CoA, presumably via malonyl ACP.