CoA-independent transacylase has characteristics distinct from those of PLA2 enzymes

CoA-independent transacylase (CoA-IT) catalyzes the transfer of arachidonic acid from acyl- to alkyl-linked phospholipids. The removal of arachidonic acid from the sn-2 position of the donor phospholipid is a PLA2-like reaction. However, examination of CoA-IT in U937 cells demonstrated that CoA-IT has many characteristics that are distinct from those of PLA2 enzymes, including activity in the absence of Ca2+, activity that was heat and acid unstable and stable in 10 mM 2-mercaptoethanol and that was inhibited by detergents. Compounds that inhibit PLA2 activity did not inhibit CoA-IT activity, including quinacrine, aristolochic acid and arachidonic acid. All of these characteristics of CoA-IT are in contrast to those of most PLA2 enzymes. These data suggest that CoA-IT is biochemically different from, and has a mechanism of action unique from PLA2 enzymes.