Accession Number : ADA112816

Title :   Importance of Extracellular Processes in the Oxygen Enhancement of Radiation Lethality.

Descriptive Note : Final rept. 15 Apr 78-31 Dec 81,


Personal Author(s) : Fridovich,Irwin

PDF Url : ADA112816

Report Date : 08 Mar 1982

Pagination or Media Count : 32

Abstract : We have explored the consequences of the biological production of O2(-) and of the enzymic scavenging of this radical by superoxide dismutases, and the scavenging of its dismutation product, H2O2, by catalases. We have shown that increased intracellular production of O2(-) can kill E. coli and that elevated superoxide dismutase protects. We have isolated two hydroperoxidases from E. coli and found one to be an active catalase, while the other was both a catalase and dianisidine peroxidase. The mechanism of oxidation of dianisidine by peroxidase was explored. A number of compounds, including methyl viologen and pyocyanine, were found to divert intracellular electron flow and to increase O2(-) production. E. coli responds adaptively to such compounds by making more superoxide dismutase. Such compounds are damaging only in the combined presence of O2 and an electron source, because only then can they mediate O2(-) production. In L. plantarum we have found that high intracellular Mn(II), approx. 25 mM, provides a functional replacement for superoxide dismutase. We have also discovered the first case of a natural gene transfer between a eukaryote (ponyfish) and a prokaryote (P. leiognathi). The gene for copper-zinc superoxide dismutase appears to have been passed from the host fish to its symbiotic bacterium. Oxygen toxicity and O2(-) toxicity has been explored in a bacterium which contains no iron compounds.

Descriptors :   *Oxygen, *Superoxides, *Peroxidases, Production, Escherichia coli, Oxidation, Toxicity, Streptococcus, Lactobacillus, Reports, Reprints

Subject Categories : Biochemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE