title: Turnover of fatty acids in the 1-position of phosphatidylethanolamine in Escherichia coli.
abstract: Phosphatidylethanolamine is the major membrane phospholipid of Escherichia coli, and two experimental approaches were used to investigate the metabolic activity of the fatty acids occupying the 1-position of this phospholipid. [3H]Acetate pulse-chase experiments with logarithmically growing cells indicated that 3-5% of the acyl groups were removed from the phosphatidylethanolamine pool/generation. The reacylation aspect of the turnover cycle was demonstrated by the incorporation of fatty acids into the 1-position of pre-existing phosphatidylethanolamine when de novo phospholipid biosynthesis was inhibited using the plsB acyltransferase mutant. 2- Acylglycerophosphoethanolamine would be the intermediate in a 1-position turnover cycle, and this lysophospholipid was identified as a membrane component that could re-esterified by a membrane-bound acyltransferase. The acyltransferase either utilized acyl-acyl carrier protein directly as an acyl donor or activated fatty acids for acyl transfer in the presence of ATP and Mg2+. Acyl-acyl carrier protein was also indicated as an intermediate in the latter reacylation reaction by the complete inhibition of phosphatidylethanolamine formation from fatty acids by acyl carrier protein-specific antibodies and by the observation that the inhibition of the acyltransferase by LiCl was reversed by the addition of acyl carrier protein. Coenzyme A thioesters were not substrates for this acyltransferase. These results suggest the existence of a metabolic cycle for the utilization of 1-position acyl moieties of phosphatidylethanolamine followed by the resynthesis of this membrane phospholipid from 2- acylglycerophosphoethanolamine by an acyl carrier protein-dependent 1-position acyltransferase.
mesh_terms: D000085:Acetates / Q000378:metabolism; D000217:Acyltransferases / Q000378:metabolism*; D002250:Carbon Radioisotopes; D002413:Cations, Divalent; D002462:Cell Membrane / Q000378:metabolism; D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism*; D007700:Kinetics; D008563:Membrane Lipids / Q000378:metabolism*; D010171:Palmitoyl Coenzyme A / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000378:metabolism*; D014316:Tritium
chemical_list: D000085:Acetates; D002250:Carbon Radioisotopes; D002413:Cations, Divalent; D005227:Fatty Acids; D008563:Membrane Lipids; D010714:Phosphatidylethanolamines; D014316:Tritium; D010171:Palmitoyl Coenzyme A; D000217:Acyltransferases; C041419:acyl-(acyl-carrier-protein)-phospholipid acyltransferase