Fatty acid chain elongation synthesis in eel (Anguilla anguilla) liver mitochondria

The properties of fatty acid chain elongation synthesis have been investiga ted in liver mitochondria of the: European eel (Anguilla anguilla). The inc orporation of [l-C-14]acetyl-CoA into fatty acids shows a specific activity of 0.43 +/- 0.05 nmol/min x mg protein (n = 6), which is more than twice h igher than that previously reported in rat liver mitochondria. Label incorp oration into fatty acids was, in mitochondria disrupted by freezing and tha wing, much higher than in intact organelles thus suggesting a probable loca lization of this pathway inside mitochondria. Only a negligible acetyl-CoA incorporation into fatty acids occurs in the absence of ATP, Mg2+ or reduce d pyridine nucleotides; NADH alone seems to be as effective as NADH + NADPH as a hydrogen donor for the reducing steps. CoASH, without effect up to 10 muM, showed a strong inhibition at higher concentrations. From the ratio o f total radioactivity and radioactivity in carboxyl carbon it can be inferr ed that in eel-liver mitochondria only chain elongation of preexisting fatt y acids occurs. A significant fatty acid chain elongation activity is also present when, instead of acetyl-CoA, [2-C-14]malonyl-CoA is used as a carbo n unit donor. Moreover, the synthesized fatty acids were actively incorpora ted into phopholipids, mainly phosphatidylcholine. phosphatidylethanolamine and sphyngomyelin. (C) 2001 Elsevier Science Inc. All rights reserved.