The interaction of phospholipase A 2 with oxidized phospholipids at the lipid-water surface with different structural organization.

Phospholipase A2 (PLA2 IB) activity towards UV-irradiated (λ=180-400nm) phospholipids in comparison to non-irradiated ones was investigated using phosphatidylcholine (PC) liposomes and mixed micelles of phosphatidylcholine and sodium deoxycholate as a membrane model. PLA2 activity, determined by spectral changes of hemoglobin (Hb) under the interaction with fatty acids (product of the phospholipolysis), correlated well with the phospholipid peroxidation degree. The present work is the first study that determines the degree of oxidation of non-fragmented OxPCs, on the base of PLA2 activity. Fragmented OxPLs have been determined as usually by analysis of MDA using spectroscopy at 532nm. Antioxidant Trolox and human blood serum reduced observed exceeding of PLA2 activity toward OxPLs, what makes this model perspective for determining the total antioxidant activity of biological liquids.