PMID:1846355
| Citation |
Gardner, PR and Fridovich, I (1991) Superoxide sensitivity of the Escherichia coli 6-phosphogluconate dehydratase. J. Biol. Chem. 266:1478-83 |
|---|---|
| Abstract |
The activity of 6-phosphogluconate dehydratase was significantly lower in extracts of aerobically grown Escherichia coli deficient in superoxide dismutase (sodAsodB) and in mutants lacking the inducible manganese-containing superoxide dismutase (sodA), exposed to the redox-cycling agent paraquat, than in the parental strain. Growth of these strains on a gluconate minimal medium was also impaired under these conditions. The enzyme was most susceptible to dioxygen in superoxide dismutase (SOD)-free extracts, and exogenous SOD afforded a concentration-dependent protection against inactivation. The amount of SOD necessary for full protection was comparable to the amount normally present in extracts of aerobic E. coli (7-36 units/mg protein), and the rate of reaction of O2- with the dehydratase was estimated to be approximately 2.0 x 10(8) M-1 s-1. The dehydratase was much less sensitive to O2 or H2O2 than to O2-. The virtual substrate, alpha-glycerophosphate, provided partial protection. Iron chelators, thiol-reactive reagents, and oxidants, including nitrite and diamide, inactivated the enzyme. Fluoride ions stabilized the dehydratase and blocked the effect of oxidants. The O2(-)-sensitive target site is proposed to be an iron-sulfur cluster which is readily destroyed by oxidation. |
| Links | |
| Keywords |
Bacterial Proteins/chemistry; Chelating Agents/chemistry; Escherichia coli/enzymology; Fluorides/chemistry; Free Radicals; Hydro-Lyases/chemistry; Hydrogen Peroxide/chemistry; Iron-Sulfur Proteins/chemistry; Oxidation-Reduction; Paraquat/pharmacology; Sulfhydryl Compounds/chemistry; Superoxides/chemistry |
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