title: Liposome effect on the cytochrome c-catalyzed peroxidation of carbonyl substrates to triplet species.
abstract: Cytochrome c exhibits peroxidase activity on diphenylacetaldehyde (DPAA) and 3-methylacetoacetone (MAA), which is greatly affected by the presence and nature of charged liposome or micelle interfaces interacting with the enzyme. The ferricytochrome c reaction with DPAA is accelerated when the enzyme is attached to negatively charged interfaces. Whatever the medium, bulk solution or negatively charged dicetylphosphate (DCP), phosphatidylcholine/phosphatidylethanolamine/cardiolipin (PC/PE/CL) liposomes, this chemiluminescent reaction is accompanied by reduction of cytochrome c to its ferrous form. In turn, MAA is oxidized by cytochrome c exclusively when bound to DCP liposomes. Contrary to DPAA oxidation, the MAA reaction is followed by bleaching of cytochrome c, reflecting damage to the hemeprotein chromophore. The cytochrome-c-catalyzed oxidation of either DPAA or MAA leads to concomitant disappearance of the enzyme charge transfer absorption band at 695 nm. This suggests that the peroxidase activity of cytochrome c involves substrate-induced loss of the methionine ligand at the iron sixth coordination position, which is favored by interaction of cytochrome c with negatively charged interfaces. Accordingly, a decrease and blue shift of the charge transfer band could be observed in cytochrome-c-containing negatively charged DCP, PC/PE/CL liposomes or lysophosphatidylethanolamine micelles in the presence of DPAA or MAA.
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, SP, Brasil. ilnantes@obelix.unicamp.br
authors.forename: I L
authors.initials: IL
authors.lastname: Nantes
authors.forename: A
authors.initials: A
authors.lastname: Faljoni-Alario
authors.forename: A E
authors.initials: AE
authors.lastname: Vercesi
authors.forename: K E
authors.initials: KE
authors.lastname: Santos
authors.forename: E J
authors.initials: EJ
authors.lastname: Bechara
mesh_terms: D000079:Acetaldehyde / Q000378:metabolism*; D000096:Acetone / Q000378:metabolism*; D000818:Animals; D002308:Cardiolipins / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism*; D007700:Kinetics; D008081:Liposomes; D008163:Luminescent Measurements; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D009195:Peroxidase / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013053:Spectrophotometry
chemical_list: D002308:Cardiolipins; D003574:Cytochrome c Group; D008081:Liposomes; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D000096:Acetone; D009195:Peroxidase; D000079:Acetaldehyde