COENZYME A-DEPENDENT CLEAVAGE OF MEMBRANE PHOSPHOLIPIDS IN SEVERAL RAT-TISSUES - ATP-INDEPENDENT ACYL-COA SYNTHESIS AND THE GENERATION OF LYSOPHOSPHOLIPIDS
T. Sugiura et al., COENZYME A-DEPENDENT CLEAVAGE OF MEMBRANE PHOSPHOLIPIDS IN SEVERAL RAT-TISSUES - ATP-INDEPENDENT ACYL-COA SYNTHESIS AND THE GENERATION OF LYSOPHOSPHOLIPIDS, Biochimica et biophysica acta, L. Lipids and lipid metabolism, 1255(2), 1995, pp. 167-176
Substantial amounts of acyl-CoA were formed when microsomes from sever
al rat tissues were incubated with varying concentrations of free CoA
and bovine serum albumin even in the absence of ATP and Mg2+. For inst
ance, 86 nmol of acyl-CoA was produced when microsomes (5 mg protein)
were incubated with 300 mu M CoA for 30 min. It was calculated that 1.
8% of total fatty acyl residues were converted to acyl-CoA. during the
incubation. No appreciable amount of acyl-CoA was formed from free fa
tty acid or from boiled microsomes under the same experimental conditi
ons. These observations indicate that acyl-CoA is formed from microsom
al lipids by an enzyme activity distinct from previously known long-ch
ain fatty acyl-CoA synthetase. The apparent K-m value for CoA and V-ma
x were 180 mu M and 20 nmol/30 min per mg protein, respectively. We fo
und that several species of acyl-CoA such as arachidonoyl-CoA were pre
ferentially synthesized through the reaction and that several types of
phospholipids actually act as acyl donors in the formation of acyl-Co
A. Phosphatidylinositol and phosphatidylcholine appear to be preferred
substrates. We confirmed that lysophosphatidylinositol and lysophosph
atidylcholine were generated along with the formation of acyl-CoA. It
seems very likely that CoA-mediated cleavage of phospholipids/ATP-inde
pendent acyl-CoA synthesis is implicated in the metabolism of certain
types of fatty acyl residues of membranous phospholipids in mammalian
cells.