Superoxide life with

Carrillo, M.C., Kanai, S., Sato, Y., Nokubo, M., Ivy, G.O. and Kitani, K. (1993). The optimal dosage of (-) deprenyl for increasing superoxide dismutase activities in several brain regions decreases with age in male Fischer 344 rats. Life Sci. 52, 1925-1934. 

Another approach to this problem is a search for the other more effective spin traps. Frejaville et al. [23] demonstrated that the half-life of spin-adduct of superoxide with 5-(diethoxyphosphoryl)-5-mcthyl-l -pyrrolinc-/V-oxide (DEMPO) is about tenfold longer than that of DMPO OOH. Despite a much more efficiency of this spin trap, its hydrophilic properties limit its use for superoxide detection in lipid membranes. Stolze et al. [24] studied the efficiency of some lipophilic derivatives of DEMPO in the reaction with superoxide. These authors demonstrated a higher stability of superoxide spin-adducts with 5-(di- -propoxypho-sphoryl)-5-methyl-1 -pyrrolinc-A -oxidc (DPPMPO) and 5-(di- -butoxyphosphoryl)-5-methyl-... 

Some aspects of the proposed Rbr/Rbo oxidative stress defense system in D. vulgaris resemble those recently suggested for oxidative stress protection in the anaerobic hyperthermophilic archaeon Pyrococcus furiosus (Jenney et al. 1999). Pyrococcus furiosus contains an Nlr-like protein with superoxide reductase activity as well as an Rbr, the genes for which are tandemly located. The microorganismic segregation of SOD/catalase between aerobes and anaerobes appears to be less distinct than for Rbo/Rbr, which, as noted above, have so far been found only in air-sensitive microbes (Kirschvink et al. 2000). The latter segregation suggests that the Rbo/Rbr oxidative stress protection system is well suited to protection of anaerobic life in an aerobic world. 

Chemical modification, particularly succinylation, or coupling to polyglycols, can also increase the plasma half-life of enzymes. Conjugation with polyethylene glycol [PEG H(OCH2CH2)nOH] has successfully been employed to stabilize and protect several therapeutic enzymes. Such modification, for example, increases the plasma half-life of superoxide dismutase from 5 h to over 30 h. PEG-coupled asparaginase was approved for general medical use by the FDA in 1994. 

Destruction of nitric oxide by superoxide in the buffers is more likely to account for the short half-life of nitric oxide in vitro. Superoxide dismutase (15-100 U/ml) substantially increased the apparent half-life of EDRF, strongly suggesting that superoxide contributes to the short biological half-life of nitric oxide. In the perfusion cascade bioassay system, the buffers are bubbled with 95% oxygen, contain 11 mM glucose as well as trace iron plus copper contamination and are incubated under the weak ultraviolet (UV) radiation of fluorescent lights. These are prime conditions for the autoxidation of glucose to form small amounts of superoxide in sufficient amounts to account for the short half-life of nitric oxide in nanomolar concentrations. The rate of reaction between superoxide and nitric oxide is 6.7 X 10 M sec L The shortest half-life of nitric oxide measured is approximately 6 sec. To achieve a half-life of 6 sec, the steady state concentration of superoxide would only need to be 17 pM, calculated as ln(2)/ (6 sec X 6.7 X 10 M" sec )-... 

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