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To counteract these reactive oxygen species, cells contain numerous antioxidant systems, including antioxidant vitamins such as vitamin C and vitamin E, and antioxidant enzymes such as superoxide dismutase, catalase, and peroxidases, [81] which detoxify the reactive species, limiting damage to the cell.
As with the chemical antioxidants, cells are protected against oxidative stress by an interacting network of antioxidant enzymes. [31] [32] Here, the superoxide released by processes such as oxidative phosphorylation is first converted to hydrogen peroxide and then further reduced to give water. This detoxification pathway is the result of ...
Numbering over 4,000 distinct chemical structures mostly from plants, such polyphenols have not been demonstrated to be antioxidants in vivo. [1] [2] [3] In vitro at high experimental doses, polyphenols may affect cell-to-cell signaling, receptor sensitivity, inflammatory enzyme activity or gene regulation.
Small changes in cellular oxidant status can be sensed by specific proteins which regulate a set of genes encoding antioxidant enzymes. Such a global response induces an adaptive metabolism including ROS elimination, the bypass of injured pathways, reparation of oxidative damages and maintenance of reducing power.
Polyphenol oxidase is an enzyme found throughout the plant and animal kingdoms, [31] including most fruits and vegetables. [32] PPO has importance to the food industry because it catalyzes enzymatic browning when tissue is damaged from bruising, compression or indentations, making the produce less marketable and causing economic loss.
Glutathione peroxidase 1, also known as GPx1, is an enzyme that in humans is encoded by the GPX1 gene on chromosome 3. [5] This gene encodes a member of the glutathione peroxidase family. Glutathione peroxidase functions in the detoxification of hydrogen peroxide, and is one of the most important antioxidant enzymes in humans. [6]
Peroxidases have been classified into three types (class I, class II and class III): ascorbate peroxidases is a class I peroxidase enzyme. [5] APXs catalyse the H 2 O 2-dependent oxidation of ascorbate in plants, algae and certain cyanobacteria. [6] APX has high sequence identity to cytochrome c peroxidase, which
The cytosols of virtually all eukaryotic cells contain a SOD enzyme with copper and zinc (Cu-Zn-SOD). For example, Cu-Zn-SOD available commercially is normally purified from bovine red blood cells. The bovine Cu-Zn enzyme is a homodimer of molecular weight 32,500. It was the first SOD whose atomic-detail crystal structure was solved, in 1975. [10]