12)įig. 1. OxPL Generation by Non-enzymatic or Enzymatic ReactionsĪ) Non-enzymatic oxidation of PLs. Fedorova and colleagues predicted that by in silico calculation, more than 20000 molecular species of OxPLs might exist in vivo. ![]() These reactions can generate extensively diverse molecular species of OxPLs in vivo. OxPLs are also generated by incorporating free oxylipins into cellular PLs by lysophospholipid acyltransferases 11) ( Fig. Among them, Alox12 and Alox15 can directly oxidize PUFA-containing PLs to form OxPLs, such as 12-hydroperoxyeicosatetraenoic acid (12-HpETE)-PL and 15-HpETE-PL, which convert rapidly into the corresponding fatty alcohols, namely, 12-hydroxyeicosatetraenoic acid (12-HETE)-PL and 15-HETE-PL by glutathione peroxidase 4 (GPx4) 11) ( Fig. Lipid oxygenases, such as lipoxygenase (LOX), cyclooxygenase (COX), and CYP, catalyze the formation of oxylipins from PUFAs. While non-enzymatic oxidation randomly generates OxPLs, enzymatic oxidation is likely to form OxPLs structure-specifically. They are subsequently converted into oxidized fatty-acyl chains, including truncated fatty acids, α,β-unsaturated fatty acids, and cyclized fatty acids through radical rearrangement 10) ( Fig. ![]() In the non-enzymatic reaction, hydroperoxides are first generated by bis-aryl hydrogen abstraction. OxPLs are generated through non-enzymatic and enzymatic reactions. OxPLs display potent biological functions, and their formation and action in many physiological and pathophysiological conditions are of particular interest. PUFA-containing PLs are susceptible to oxidation to form oxidized phospholipids (OxPLs) by reactive oxygen species (ROS) or oxygenases or both. In contrast, polyunsaturated fatty acids (PUFAs), such as linoleic acid (LA), arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), are mainly located at the sn-2 position. Saturated or monounsaturated fatty acids are usually present in the sn-1 position. ![]() Their structures consist of a glycerol backbone with a polar head-group linked to the sn-3 position and two fatty acyls linked to the sn-1/ sn-2 positions. Phospholipids (PLs) are the major components of cell membranes.
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