ENZYMATIC ANTIOXIDANTS |
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SUPER OXIDE DISMUTASE (SOD) Reactions catalyzed: [O2- + SOD → H2O2 + O2] Various isoforms: ecSOD (extracellular); Mn-SOD (mitochondrial); Cu/Zn-SOD (intracellular) |
CATALASE – Location: peroxisome. Reaction catalyzed: [2 H2O2 + catalase → 2 H2O + O2] |
GLUTATHIONE PEROXIDASE – Location: mitochondrion, cytosol, and systemic circulation. Glutathione (GSH or glutamyl-cysteinyl-glycine tripeptide): the reduced -SH of GSH is oxidized to disulfide GSSG. Glutathione peroxidase-catalyzed reation: [GSH + 2 H2O2 → GSSG + H2O + O2] Glutathione reductase-catalyzed reaction: [GSSG → GSH] at the expense of [NADH → NAD+] and/or [NAD(P)H → NAD(P)+] |
ENZYMATIC – NONENZYMATIC INACTIVATION OF FREE RADICALS. NITRIC OXIDE SYNTHASE Location: membrane. |
Isoforms: |
eNOS (endothelial): good |
nNOS (neuronal): good |
iNOS (inducible-inflammatory): bad |
O2- and nitric oxide (NO) are consumed in this process with the creation of reactive nitrogen species (RNS). O2- + NO → ONOO-(peroxynitrite) + tyrosine → nitrotyrosine. Nitrotyrosine reflects redox stress and leaves a measurable footprint. NO the good; O2• the bad; ONOO- the ugly * |
NONENZYMATIC ANTIOXIDANTS |
Vitamins (A, C, and E): Thiols: Sulfhydryl (-SH)-containing molecules. Albumin: Is an antioxidant because of it is a thiol-containing macromolecule. Apoproteins: Ceruloplasmin and transferrin. Bind copper and iron in forms, which cannot participate in the Fenton reaction. Uric acid: Early on in the atherosclerotic process in physiologic ranges: antioxidant. PARADOX: Late in elevated range prooxidant with loss of supporting antioxidants above and in a milieu of oxidative – redox stress within the atherosclerotic intima. In MS, T2DM and advanced vulnerable atherosclerotic plaques SOD, Catalase, and GPX are depleted. The Urate Redox Shuttle. PARADOX: antioxidants may become prooxidant in a certain milieu. |