COENZYME A-DEPENDENT MODIFICATION OF FATTY ACYL CHAINS OF RAT-LIVER MEMBRANE PHOSPHOLIPIDS - POSSIBLE INVOLVEMENT OF ATP-INDEPENDENT ACYL-COA SYNTHESIS
T. Sugiura et al., COENZYME A-DEPENDENT MODIFICATION OF FATTY ACYL CHAINS OF RAT-LIVER MEMBRANE PHOSPHOLIPIDS - POSSIBLE INVOLVEMENT OF ATP-INDEPENDENT ACYL-COA SYNTHESIS, Journal of lipid research, 36(3), 1995, pp. 440-450
Certain species of fatty acyl chains of microsomal lipids from rat hep
atocytes underwent desaturation when the microsomal fraction was incub
ated with CoA and NADH. For instance, 18:0, 18:2(n-6), and 20:3(n-6) i
ncorporated into membrane lipids were gradually converted to 18:1(n-9)
, 18:3(n-6), and 20:4(n-6), respectively. Further, 20:5(n-3) and 18:3(
n-6) were metabolized to 22:5(n-3) and 20:4(n-6), respectively, throug
h chain elongation or chain elongation plus subsequent desaturation wh
en malonyl-CoA was present. In contrast to esterified fatty acids, neg
ligible change was observed for free fatty acids under the same experi
mental conditions. It is apparent that ATP-independent acyl-CoA synthe
sis is implicated in such enzymatic modification of fatty acyl chains.
The presence of either gel-filtered cytosol or bovine serum albumin m
arkedly potentiated the reaction. However, the addition of ATP and Mg2
+ did not accelerate the overall reaction induced in the presence of C
oA alone. These results suggest that the pathway of CoA-dependent/ATP-
independent modification of fatty acyl chains is sufficiently active t
o account for the desaturation and chain elongation of fatty acids est
erified in membrane lipids, especially phospholipids, of living cells.