Table 6

Antioxidants: catalytic – enzymatic inactivation of free radicals.

Enzymatic Antioxidants

    SUPER OXIDE DISMUTASE (SOD)
[O2- + SOD → H2O2 + O2] ecSOD (extracellular) MnSOD (mitochondrial) CuZnSOD (intracellular)

    CATALASE
– Location: peroxisome [2H2O2 + catalase → 2 H2O + O2]

    GLUTATHIONE PEROXIDASE
– Location: mitochondrion – cytosol and systemic circulation. (Glutamyl-cysteinyl-glycine tripeptide) glutathione reduced -SH to the oxidized disulfide GSSG. (Glutathione peroxidase) [GSH + 2H2O2 → GSSG + H2O + O2] (Glutathione reductase) [GSSG → GSH] at the expense of [NADH → NAD+] and/or [NAD(P)H → NAD(P)+]

    NOS (nitric oxide synthase).
– Location: membrane Isoforms: (e)NOS (endothelial): good (n)NOS (neuronal): good (i)NOS (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 [42]

Nonenzymatic Antioxidants

    URIC ACID

    VITAMIN A
,
    VITAMIN
    C
,
    and
    VITAMIN
    E

    THIOLS
: Sulfhydryl (-SH) containing molecules.

    ALBUMIN
: Is an antioxidant due to thiol containing compounds.

    APOPROTEINS
: Ceruloplasmin and transferrin. Bind copper and iron in forms which cannot participate in the Fenton reaction


Hayden and Tyagi Nutrition Journal 2004 3:4   doi:10.1186/1475-2891-3-4

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