Leukocytic Myeloperoxidase-mediated Formation of Bromohydrins and Lysophospholipids from Unsaturated Phosphatidylcholines

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Abstract

Using MALDI-TOF mass spectrometry, we have shown that leukocytic myeloperoxidase (MPO) in the presence of its substrates (H2O2 and Br−) does not induce any changes in saturated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine. Incubation of liposomes prepared from mono-unsaturated phosphatidylcholine (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) with the (MPO + H2O2 + Br−) system resulted in formation of bromohydrins as the main products. 1-Palmitoyl-2-hydroxy-sn-glycero-3-phosphocholine (lysophosphatidylcholine) was the main product of the reaction of polyunsaturated phosphatidylcholine (1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine) with the (MPO + H2O2 + Br−) system. The formation of lysophospholipids as well as of bromohydrins was not observed when the enzyme or one of its substrates (H2O2 or Br−) was absent from the incubation medium, or if an inhibitor of MPO (sodium azide) or hypobromite scavengers (taurine or methionine) were added. Thus, it can be postulated that the formation of bromohydrins as well as lysophospholipids by the (MPO + H2O2 + Br−) system results from reactions of hypobromite formed during MPO catalysis with double bonds of acyl chains of phosphatidylcholine. Such destructive processes may take place in vivo in membrane-or lipoprotein-associated unsaturated lipids in centers of inflammation.

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