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Query: UNIPROT:P04040 (Catalase)
 3,577 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several enzymatic and nonenzymatic reactions play important roles in the physiologic neutralization of hydrogen peroxide (H2O2) in the anterior segment of the eye. The nonenzymatic reactions are particularly important in the aqueous humor, where enzymes are normally absent and high levels of ascorbate are present. One of ascorbate's presumed functions is to protect the lens and retina from the damaging effects of ultraviolet radiation. It also appears to act as an antioxidant for the removal of H2O2. Although H2O2 is frequently a product of antioxidant reactions, the low oxygen tension of the aqueous humor and the absence of trace elements apparently account for the relatively low concentrations of H2O2. This property of aqueous humor is important because high concentrations of H2O2 are toxic to both the lens and the cornea. This damage is exacerbated by the removal of glucose or by inhibition of glutathione reductase--an indication of the importance of the glutathione redox cycle in protecting against endothelial damage induced by H2O2. Catalase also protects the tissues bordering the anterior chamber from H2O2-induced damage. Decreasing catalase activity by treatment with 3-aminotriazole increases the time required for H2O2 clearance from the anterior chamber, thereby allowing more time for H2O2 to produce damage. A decline of catalase activity with age has been observed in the iris and corneal endothelium of rabbits.
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PMID:Physiologic neutralization mechanisms and the response of the corneal endothelium to hydrogen peroxide. 240 81

Non-pigmented epithelial (NPE) cells and pigmented epithelial (PE) cells were dissociated from bovine ciliary processes by brief digestion with pronase and grown in a culture medium containing high fetal bovine serum for at least 25 generations. Both types of cells grown to confluence showed the presence of intermediate junctions with associated tonofilaments. PE cells were distinguished from NPE cells by pigmentation during the early passages. Gamma-glutamyl transpeptidase activity was associated almost exclusively with NPE cells and proved to be a useful enzymatic marker to distinguish NPE from PE. A comparison was made between NPE and PE cells as to the levels of enzymes involved in the detoxification of active oxygen species. Catalase, Se-dependent glutathione peroxidase and superoxide dismutase activities were significantly higher in NPE than in PE cells. The results suggest that NPE cells play the major role in detoxification of active oxygen species during aqueous humor formation.
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PMID:Bovine non-pigmented and pigmented ciliary epithelial cells in culture: comparison of catalase, superoxide dismutase and glutathione peroxidase activities. 290 72