Fatty acid biosynthesis by a particulate preparation from germinating pea.
1. Fatty acid synthesis was studied in microsomal preparations from germinating pea (Pisum sativum). 2. The preparations synthesized a mixture of saturated fatty acids up to a chain length of C(24) from [(14)C]malonyl-CoA. 3. Whereas hexadecanoic acid was made de novo, octadecanoic acid and icosanoic acid were synthesized by elongation. 4. The products formed during [(14)C]malonyl-CoA incubation were analysed, and unesterified fatty acids and polar lipids were found to be major products. [(14)C]Palmitic acid represented a high percentage of the acyl-carrier protein esters, whereas (14)C-labelled very-long-chain fatty acids were mainly present as unesterified fatty acids. CoA esters were minor products. 5. The addition of exogenous lipids to the incubation system usually resulted in stimulation of [(14)C]malonyl-CoA incorporation into fatty acids. The greatest stimulation was obtained with dipalmitoyl phosphatidylcholine. Both exogenous palmitic acid and dipalmitoyl phosphatidylcholine increased the amount of [(14)C]-stearic acid synthesized, relative to [(14)C]palmitic acid. Addition of stearic acid increased the amount of [(14)C]icosanoic acid formed. 6. [(14)C]Stearic acid was elongated more effectively to icosanoic acid than [(14)C]stearoyl-CoA, and its conversion was not decreased by addition of unlabelled stearoyl-CoA. 7. Incorporation of [(14)C]malonyl-CoA into fatty acids was markedly decreased by iodoacetamide and 5,5'-dithiobis-(2-nitrobenzoic acid). Palmitate elongation was sensitive to arsenite addition, and stearate elongation to the presence of Triton X-100 or fluoride. The action of fluoride was not, apparently, due to chelation. 8. The microsomal preparations differed from soluble fractions from germinating pea in (a) synthesizing very-long-chain fatty acids, (b) not utilizing exogenous palmitate-acyl-carrier protein as a substrate for palmitate elongation and (c) having fatty acid synthesis stimulated by the addition of certain complex lipids.
D002614:Chelating Agents / Q000494:pharmacology; D003902:Detergents / Q000494:pharmacology; D007887:Fabaceae / Q000187:drug effects / Q000378:metabolism; D005227:Fatty Acids / Q000096:biosynthesis*; D008055:Lipids / Q000494:pharmacology; D008861:Microsomes / Q000378:metabolism; D010946:Plants, Medicinal; D011663:Pulmonary Surfactants / Q000494:pharmacology; D012639:Seeds / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000494:pharmacology
D002614:Chelating Agents; D003902:Detergents; D005227:Fatty Acids; D008055:Lipids; D011663:Pulmonary Surfactants; D013438:Sulfhydryl Compounds