Synthesis of a novel acetylated neutral lipid related to platelet-activating factor by acyl-CoA:1-O-alkyl-2-acetyl-sn-glycerol acyltransferase in HL-60 cells

J Biol Chem. 1988 Feb 25;263(6):2593-6.


Acyl-CoA:1-O-hexadecyl-2-acetyl-sn-glycerol acyl-transferase, a newly detected enzyme related to platelet-activating factor metabolism, has been characterized in microsomes of a human leukemia cell line (HL-60 cells). It has a sharp pH optimum of 6.8, does not require divalent metal ions, is stable at preincubation temperatures up to 45 degrees C, and among a variety of acyl-CoA thioesters (8:0-20:4) tested, linoleoyl-CoA is the best substrate. Km and Vmax values for 1-O-hexadecyl-2-acetyl-sn-glycerol acyltransferase are 8.5 microM and 1.7 nmol/min/mg of protein, respectively. For comparative purposes acyl-CoA:1,2-dioleoyl-sn-glycerol acyltransferase was also characterized in HL-60 microsomes. It has a relatively broad pH optimum of 6.1, is stimulated 1.4-fold by Mg2+, is relatively labile at preincubation temperatures higher than 25 degrees C, and among the various acyl-CoA thioesters tested, myristoyl-CoA is the best substrate. In substrate competition experiments, we found 1-O-hexadecyl-2-oleoyl-sn-glycerol is a competitive inhibitor (Ki = 32 microM). Our findings indicate acyl-CoA:1-O-hexadecyl-2-acetyl-sn-glycerol acyltransferase in HL-60 cells is distinctly different from acyl-CoA:1,2-dioleoyl-sn-glycerol acyltransferase. Our experimental results demonstrate that the unique enzyme activity characterized in this report also is expressed in intact HL-60 cells.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acyl Coenzyme A / metabolism
  • Acyltransferases / metabolism*
  • Cations, Divalent / pharmacology
  • Chromatography, Thin Layer
  • Dithiothreitol / pharmacology
  • Humans
  • Hydrogen-Ion Concentration
  • Kinetics
  • Leukemia, Myeloid, Acute / enzymology*
  • Magnesium / metabolism
  • Microsomes / metabolism
  • Platelet Activating Factor / biosynthesis*
  • Temperature
  • Tumor Cells, Cultured / enzymology


  • Acyl Coenzyme A
  • Cations, Divalent
  • Platelet Activating Factor
  • linoleoyl-coenzyme A
  • Acyltransferases
  • acyl-CoA-1-O-alkyl-2-acetyl-sn-glycerol acyltransferase
  • Magnesium
  • Dithiothreitol