Enzymes superoxide dismutases

Figure S.l The enzyme superoxide dismutase (SOD). SOD is a P structure comprising eight antiparallel P strands (a). In addition, SOD has two metal atoms, Cu and Zn (yellow circles), that participate in the catalytic action conversion of a superoxide radical to hydrogen peroxide and oxygen. The eight p strands are arranged around the surface of a barrel, which is viewed along the barrel axis in (b) and perpendicular to this axis in (c). [(a) Adapted from J.S. Richardson. The stmcture of SOD was determined in the laboratory of J.S. and D.R. Richardson, Duke University.)...

Superoxide is a free radical form of oxygen (02 ) that is damaging to cells. Superoxide is scavenged by the enzyme superoxide dismutase used by neutrophils to destroy microbes in the body. 

Tissues are protected from oxygen toxicity caused by the superoxide free radical by the specific enzyme superoxide dismutase. 

Superoxide is formed (reaction 1) in the red blood cell by the auto-oxidation of hemoglobin to methemo-globin (approximately 3% of hemoglobin in human red blood cells has been calculated to auto-oxidize per day) in other tissues, it is formed by the action of enzymes such as cytochrome P450 reductase and xanthine oxidase. When stimulated by contact with bacteria, neutrophils exhibit a respiratory burst (see below) and produce superoxide in a reaction catalyzed by NADPH oxidase (reaction 2). Superoxide spontaneously dismu-tates to form H2O2 and O2 however, the rate of this same reaction is speeded up tremendously by the action of the enzyme superoxide dismutase (reaction 3). Hydrogen peroxide is subject to a number of fates. The enzyme catalase, present in many types of cells, converts... 

It is possible that dietary flavonoids participate in the regulation of cellular function independent of their antioxidant properties. Other non-antioxidant direct effects reported include inhibition of prooxidant enzymes (xanthine oxidase, NAD(P)H oxidase, lipoxygenases), induction of antioxidant enzymes (superoxide dismutase, gluthathione peroxidase, glutathione S-transferase), and inhibition of redox-sensitive transcription factors. 

The enzyme superoxide dismutase regulates the level of superoxide by catalyzing conversion of superoxide to hydrogen peroxide and molecular oxygen. 

The process of the superoxide-dependent PCL that can be inhibited by enzyme superoxide dismutase (SOD) is shown in Figure 2. Luminol can be replaced by lucigenin. In this case, only the first maximum is detected. This variant of the system is useful for SOD activity measurements. The system is very sensitive and rugged therefore, it is even possible to perform the enzyme determination in whole blood [22],... 

General descriptors may be related to the metabolism responses in the biofilm. Biofilm algae have several mechanisms to counterbalance the damage caused by the toxicants. Environmental stress produces oxidative damage in the cells, which can be tracked down by means of the analysis of many enzymes (superoxide dismutase, catalase, peroxidase, etc.) that function as effective quenchers of reactive oxygen species (ROS). 

The enzyme superoxide dismutase (SOD) occurs in three forms in mammalian systems (1) CuZnSOD (SOD1) found in the cytosol, (2) MnSOD (SOD2) found in mitochondria, and (3) CuZnSOD found in extracellular space (SOD3). Additionally, many bacterial SOD enzymes contain iron. SOD 1 has been discussed in detail... 

Frontotemporal dementia involves an early and primary degenerative process of frontal and/or temporal cortex. Several disorders fall under this rubric, such as Pick s disease and the dementia associated with amyotrophic lateral sclerosis (ALS). ALS is a degenerative disease of upper motor neurons that is sometimes accompanied by a frontal lobe dementia (Vercelletto et al. 1999 Abe et al. 1997). ALS has been associated with mutations in the free radical scavenging enzyme superoxide dismutase 1 (Price et al. 1997). Pick s disease is associated histologically with a loss of neurons and cytoplasmic Pick bodies in surviving neurons. 

All aerobic organisms contain substances that help prevent injury mediated by free radicals, and these include antioxidants such as a-tocopherol and the enzymes superoxide dismutase and glutathione peroxidase. When the protective effect of the antioxidants is overwhelmed by the production of reactive oxygen species, the intracellular milieu becomes oxidative, leading to a state known as oxidative stress (Halliwell and Gutteridge, 1999). Thus the balance between the generated free radicals and the efficiency of the protective antioxidant system determines the extent of cellular damage. 

Defenses against ROS accumulation include the enzymes superoxide dismutase, glutathione peroxidase, and catalase. 

Mammalian systems have enzymes, superoxide dismutases (SODs), which dismutate two molecules of superoxide into one of hydrogen peroxide and one of oxygen. The enzymes are located in the cytosol and mitochondria. The location in the mitochondria is important because ROS are often produced there, and one form of SOD is inducible, as a result of oxidative stress. 

The superoxide produced can be detoxified by the action of the enzyme superoxide dismutase, which produces hydrogen peroxide. The hydrogen peroxide is then removed by catalase (Fig. 7.41)... 

To prevent oxidative damage by 02, cells have several forms of the enzyme superoxide dismutase,... 

Cylinders and barrels. The twisted P sheets of proteins are often curved to form structures known as P cylinders or p barrels (Fig. 2-16).113 114 Simple cylinders formed by parallel P strands form the backbones of the electron transport protein plastocyanin, the enzyme superoxide dismutase, the oxygen carrier... 

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