Cellular Derived Blood Proteins and Enzymes

BioFiles 2006, 1.5, 4.

BioFiles 2006, 1.5, 4.

Superoxide Dismutase

Cell damage is induced by reactive oxygen species (ROS). ROS are either free radicals, reactive anions containing oxygen atoms, or molecules containing oxygen atoms that can either produce free radicals or are chemically activated by them. Examples are hydroxyl radical, superoxide, hydrogen peroxide, and peroxynitrite. The main source of ROS in vivo is aerobic respiration, although ROS are also produced by peroxisomal β-oxidation of fatty acids, microsomal cytochrome P450 metabolism of xenobiotic compounds, stimulation of phagocytosis by pathogens or lipopolysaccharides, arginine metabolism, and tissue specific enzymes. Under normal conditions, ROS are cleared from the cell by the action of superoxide dismutase (SOD), catalase, or glutathione (GSH) peroxidase. The main damage to cells results from the ROS-induced alteration of macromolecules such as polyunsaturated fatty acids in membrane lipids, essential proteins, and DNA. Additionally, oxidative stress and ROS have been implicated in disease states, such as Alzheimer's disease, Parkinson's disease, cancer, and aging. Superoxide Dismutase (SOD) catalyzes the reduction of superoxide anions to hydrogen peroxide. KM for O2 for bovine SOD = 0.35 mM. The bovine enzyme exists as a dimeric copper-zinc containing protein with a molecular weight of 2 X 16,300 Da. The E. coli enzyme exists as a dimeric manganese or iron containing glycoprotein with a molecular weight of 2 x 22,000 Da. The human enzyme exists as a tetrameric copper-zinc or manganese containing glycoprotein with a molecular weight of 2 X 23‑28,300 Da. Covalent conjugation of superoxide dismutase with polyethylene glycol (PEG) has been found to increase the circulatory half-life and provides prolonged protection from partially reduced oxygen species.


Superoxide Dismutase

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Materials

 

     
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