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Oxygen Terrestrial distribution: 3rd of the most frequently occurring elements: (H, He, O2) 168O (99 %) 188O (izotóp) Bioinorganic importance of oxygen: ORGANOGENIC element
O2+ oxygen ion: no biological importance O oxygen atom: reactive (decomposition O3) O2- superoxide anion: UV, enzyme reactions (xanthinoxidase, NADPH-oxidase) O22- peroxide anion: dissociation of H2O2 OH hydroxy free radical: decomposition of H2O2 HO2 hydroperoxy free radical
Bioinorganic Chemistry Activated derivatives
d*2px p*2py, pz p 2py, pz d 2px 1O2 singlet oxygen Ground state Singlet state
Enzyme reactions Inflammation Drugs UV Light Smoking Radiation Pollutants (O3, NO2) Oxygen Free Radicals
Oxygen Free Radicals Membrane lipids Nucleic acids Proteins Cancer Emphysema Neurological Disorders Cardiovascular Cataract Aging
Reactive Oxygen Species Cell adhesion DNA damage Cancer Inflammation Inactivation of NO Oxidation of LDL Membrane damage Microcirculation injury Hypertension Atherosclerosis Cell injury (Cancer therapy)
Activator enzymes: dioxygenase 1. Oxygenases monoxygenase 2. OxydasesO2-, H2O2 or 2H2O electron acceptor
A Protection from superoxide and peroxide 1. Superoxide dismutase systems 2. Catalase (heme) 3. Peroxidase systems (heme)
Superoxide Dismutase SOD-Cu2+ + O2.- SOD-Cu1+ + O2 SOD-Cu1+ + O2.- + 2H+ SOD-Cu2+ + H2O2
Proteins with catalytic behaviours - Enzymes Catalase catalyzes the breakdown of hydrogen peroxide, (H2O2) a toxic by product of metabolic reactions, to the harmless substances, water and oxygen.
O2 + free electron O2- superoxide radical H2O Physiological state superoxide dismutase H2O2 GSH glutathion peroxidase H2O catalase GSSG H2O H2O + O2 Pathological state Haber-Weiss’ reaction H2O2 + O2-superoxide radical O2 + OH- + ·OH hydroxyl radical Fenton’s reaction Fe3++ OH- + ·OH hydroxyl radical H2O2 + Fe2+
Oxygen radical production by phagocytes O2 Respiratory burst Bacterium Bacterium Bakterie Bakterie Bakterie NADPH O2•(Superoxid) NADPH Oxidase NADP+ Superoxid dismutase Fe2+ Bakt Cl - H2O2 Fe3+ erie terie Myeloperoxidase Bak MACROPHAG Phagolysosom OH- • HOCl •
Biochemistry Reactive Oxygen Species XO NOX Peroxidases O2- NOSunc NO2- Cl- Br- NO2 HOCl HOBr Fenton H2O2 Antimicrobial LOOH MAPK NFkB p53 Aconitase inhibition COX LipOX