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REACTIVITY OF PHOTOCHEMICALLY‐GENERATED LIPID HYDROPEROXIDES IN CELL MEMBRANES WITH GLUTATHIONE PEROXIDASE
Author(s) -
THOMAS JAMES P.,
GIROTTI ALBERT W.
Publication year - 1989
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1989.tb04089.x
Subject(s) - chemistry , glutathione peroxidase , membrane , glutathione reductase , glutathione , phosphatidylcholine , hematoporphyrin , peroxidase , liposome , biochemistry , gpx3 , horseradish peroxidase , gpx4 , antioxidant , enzyme , phospholipid , organic chemistry , photodynamic therapy
The ability of glutathione peroxidase (Gpx) to catalyze the reductive inactivation of phot‐ochemically‐generated lipid hydroperoxides (LOOHs) was investigated, using hematoporphyrin derivative (HPD) as a photosensitizing agent and erythrocyte ghosts as membrane targets. Glutathione peroxidase was reactive toward photoperoxidized membranes only after their exposure to phospholi‐pase A 2 (PLA 2 )‐ Iodometrically‐determined LOOH values were typically 30–40% greater than values measured by enzymatic assay using Gpx and glutathione reductase. A consistent result was obtained when photooxidized membranes were treated with PLA 2 and GSH/Gpx followed by iodometric assay, viz. persistence of approximately 40% of the starting LOOH. Whereas photooxidized egg phosphatidylcholine liposomes underwent total LOOH loss when incubated with PLA 2 and GSH/Gpx, no net loss was observed with photooxidized cholesterol/dimyristoyl‐phosphatidylcholine liposomes. The results suggest that cholesterol hydroperoxides in ghost membranes account for the Gpx‐resistant fraction of LOOHs.