John G. Scandalios

Molecular oxygen (O2) is the premier biological electron acceptor that serves vital roles in fundamental cellular functions. However, with the beneficial properties of O2 comes the inadvertent formation of reactive oxygen species (ROS) such as superoxide (O2*-), hydrogen peroxide, and hydroxyl radical (OH*). If unabated, ROS pose a serious threat to or cause the death of aerobic cells. To minimize the damaging effects of ROS, aerobic organisms evolved non-enzymatic and enzymatic antioxidant defenses. The latter include catalases, peroxidases, superoxide dismutases, and glutathione S-transferases (GST). Cellular ROS-sensing mechanisms are not well understood, but a number of transcription factors that regulate the expression of antioxidant genes are well characterized in prokaryotes and in yeast. In higher eukaryotes, oxidative stress responses are more complex and modulated by several regulators. In mammalian systems, two classes of transcription factors, nuclear factor kB and activator protein-1, are involved in the oxidative stress response. Antioxidant-specific gene induction, involved in xenobiotic metabolism, is mediated by the "antioxidant responsive element" (ARE) commonly found in the promoter region of such genes. ARE is present in mammalian GST, metallothioneine-I and MnSod genes, but has not been found in plant Gst genes. However, ARE is present in the promoter region of the three maize catalase (Cat) genes. In plants, ROS have been implicated in the damaging effects of various environmental stress conditions. Many plant defense genes are activated in response to these conditions, including the three maize Cat and some of the superoxide dismutase (Sod) genes.

The oxygen paradox - biochemistry of active oxygen redox regulation by the HIV-1 TAT transcritional factor oxidative damage to DNA and its repair the antioxidative stress in eukaryotes transcriptional regulators of oxidative stress responses oxidative stress, gene expression and the aging process superoxide dismutases in bacteria and pathogen protists superoxide dismutase - studies in the yeast saccharomyces cerevisiae molecular genetics of superoxide dismutases in plants bacterial catalases biochemistry, molecular biology and cell biology of yeast and fungal catalases catalases in plants - gene structure, properties, regulation and expression the structure of catalases mediation of signal transduction by oxidants the oxidative burst and its roles in signal transduction and response of stressed plants the NADPH oxidase of leukocytes osicative burst-mediated defense responses in plant disease resistance gluta-thione reductase - regulation and role in oxidative stress oxidative stress in mitochondria oxygen metabolism and electron transport in photosynthesis ascorbate peroxidase and monodehydroscorbate reducatase - key enzymes for hydrogen peroxide-scavenging system in plants oxidandants, antioxidants and aging reactive oxygen and apoptosis role of sod in neurodegenerative disease free radicals - dietary advantages and disadvantages defense against photooxidative damage in plants air pollution and free radical protection responses of plants.

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