title: Singlet oxygen generation from the decomposition of alpha-linolenic acid hydroperoxide by cytochrome c and lactoperoxidase.
abstract: Generation of singlet oxygen is first investigated in the decomposition of polyunsaturated lipid peroxide, alpha-linolenic acid hydroperoxide (LAOOH), by heme-proteins such as cytochrome c and lactoperoxidase. Chemiluminescence and electron spin resonance methods are used to confirm the singlet oxygen generation and quantify its yield. Decomposition products of LAOOH are characterized by HPLC-ESI-MS, which suggests that singlet oxygen is produced via the decomposition of a linear tetraoxide intermediate (Russell's mechanism). Free radicals formed in the decomposition are also identified by the electron spin resonance technique, and the results show that peroxyl, alkyl, and epoxyalkyl radicals are involved. The changes of cytochrome c and lactoperoxidase in the reaction are monitored by UV-visible spectroscopy, revealing the action of a monoelectronic and two-electronic oxidation for cytochrome c and lactoperoxidase, respectively. These results suggest that cytochrome c causes a homolytic reaction of LAOOH, generating alkoxyl radical and then peroxyl radical, which in turn releases singlet oxygen following the Russell mechanism, whereas lactoperoxidase leads to a heterolytic reaction of LAOOH, and the resulting ferryl porphyryl radical of lactoperoxidase abstracts the hydrogen atom from LAOOH to give peroxyl radical and then singlet oxygen. This observation would be important for a better understanding of the damage mechanism of cell membrane or lipoprotein by singlet oxygen and various radicals generated in the peroxidation and decomposition of lipids induced by heme-proteins.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China.
authors.forename: Shuna
authors.initials: S
authors.lastname: Sun
authors.forename: Zhijuan
authors.initials: Z
authors.lastname: Bao
authors.forename: Huimin
authors.initials: H
authors.lastname: Ma
authors.forename: Deqing
authors.initials: D
authors.lastname: Zhang
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Zheng
mesh_terms: D002851:Chromatography, High Pressure Liquid; D045304:Cytochromes c / Q000737:chemistry / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D007700:Kinetics; D007784:Lactoperoxidase / Q000737:chemistry / Q000378:metabolism*; D008042:Linolenic Acids / Q000737:chemistry* / Q000378:metabolism; D008054:Lipid Peroxides / Q000737:chemistry* / Q000378:metabolism; D049449:Luminescence; D008956:Models, Chemical; D015394:Molecular Structure; D010084:Oxidation-Reduction; D026082:Singlet Oxygen / Q000737:chemistry* / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization; D013053:Spectrophotometry; D017962:alpha-Linolenic Acid / Q000737:chemistry* / Q000378:metabolism
chemical_list: D008042:Linolenic Acids; D008054:Lipid Peroxides; D017962:alpha-Linolenic Acid; D026082:Singlet Oxygen; C025998:13-hydroperoxylinolenic acid; D045304:Cytochromes c; D007784:Lactoperoxidase