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J D Stahl

Publications and source records attributed to J D Stahl.

7 recordsLinked to original sources
PubMed2000

Glutathione-mediated mineralization of 14C-labeled 2-amino-4,6-dinitrotoluene by manganese-dependent peroxidase H5 from the white-rot fungus Phanerochaete chrysosporium.

Manganese-dependent peroxidase (MnP) H5 from the white-rot fungus Phanerochaete chrysosporium, in the presence of either Mn(II) (10 mM) or GSH (10 mM). was able to mineralize 14C-U-ring-labeled 2-amino-4,6-dinitrotoluene (2-A-4,6-DNT) up to 29% in 12 days. When both Mn(II) and GSH were present, the mineralization extent reached 82%. On the other hand, no significant mineralization was observed in the absence of both Mn(II) and GSH, suggesting the requirement of a mediator [either Mn(II) or GSH] for the degradation of 2-A-4,6-DNT by MnP. Using electron spin resonance (ESR) techniques, it was found that the glutathionyl free radical (GS*) was produced through the oxidation of GSH by MnP in the presence as well as in the absence of Mn(II). GS* was also generated through the direct oxidation of GSH by Mn(III). Our results strongly suggest the involvement of GS* in the GSH-mediated mineralization of 2-A-4,6-DNT by MnP.

Aniline Compounds↗
PubMed1995

Reduction of quinones and radicals by a plasma membrane redox system of Phanerochaete chrysosporium.

Quinones which are produced during the mineralization of lignin and xenobiotics by the white rot fungus Phanerochaete chrysosporium were reduced by a plasma membrane redox system of the fungus. Both intracellular enzymes and the plasma membrane redox system were able to reduce 1,4-benzoquinone. However, no quinone reductase activity was observed with the extracellular culture fluid. The intracellular reductase activity had a pH optimum between 6.0 and 7.0 and a Km of 150 microM. Reduction of 1,4-benzoquinone by the plasma membrane redox system had a pH optimum between 7.5 and 8.5 and exhibited saturation kinetics (Km = 11 microM, Vmax = 16 nmol/min/mg mycelia dry weight). Ferricyanide totally inhibited the quinone reduction until the ferricyanide was completely reduced by the membrane. Radicals (chlorpromazine and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS)) that can be generated by the lignin peroxidases were also reduced by the plasma membrane redox system. Reduction of the ABTS cation radical also totally inhibited quinone reduction until the radical was completely reduced. Finally, quinone reduction rates were identical after the reduction of ferricyanide, ABTS cation radical, or quinone, suggesting that the plasma membrane redox system may actually protect the fungus from oxidative damage from free radicals generated by the lignin degrading system.

Basidiomycota↗
PubMed1995

Properties of a transplasma membrane redox system of Phanerochaete chrysosporium.

A transplasma membrane redox system of Phanerochaete chrysosporium was studied using ferricyanide, a membrane-impermeable electron acceptor. Rates of reduction were dependent upon initial ferricyanide concentration and mycelial mass. Specific activities of 12 +/- 2 nmol/min/mg mycelia (dry wt) were consistently obtained using nutrient-sufficient mycelia at pH 8.0 and 10 mM ferricyanide. Upon nutrient limitation (either carbon or nitrogen), activity decreased. Reduction was inhibited by carbonyl cyanide m-chloromethoxyphenyl hydrazone, 2,4-dinitrophenol, and sodium azide but not by potassium cyanide at 100 nmol/mg mycelia. Ferricyanide reduction and proton export rates increased with pH above the physiological pH for the fungus. The stimulation in proton exported by the addition of ferricyanide was equal to the rate of ferricyanide reduced at pH 8.0 when Hepes buffer was used. The relevance of these findings with regard to the physiological pH optimum of the fungus and the metabolism of pollutants by this fungus is discussed.

Cell Membrane↗
PubMed1993

Plasma membrane dependent reduction of 2,4,6-trinitrotoluene by Phanerochaete chrysosporium.

A plasma membrane redox system of Phanerochaete chrysosporium was found to reduce 2,4,6-trinitrotoluene (TNT). Reduction required intact, live mycelia. No reduction was observed with either supplemented (NADPH, NADH or ATP) or unsupplemented extracellular or intracellular fractions, either under aerobic or anaerobic conditions. Reduction was inhibited by potassium ferricyanide, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium, carbonyl cyanide p-trifluoromethoxyphenyl hydrazone, 2,4-dinitrophenol, sodium azide, and tetranitroblue tetrazolium but not by nitroblue tetrazolium, 2,3,5-triphenyl tetrazolium and blue tetrazolium. At higher pH, the rate of reduction as well as proton pumping was enhanced.

Basidiomycota↗
PubMed1993

Metabolism and detoxification of TNT by Phanerochaete chrysosporium.

Several lines of evidence suggest that TNT detoxification by Phanerochaete chrysosporium is through reduction. Rates of TNT reduction were directly correlated with mycelial mass and TNT concentration. Toxicity was inversely related to the amount of fungus. TNT toxicity was identical in both ligninolytic and nonligninolytic cultures. Rapid disappearance of the reduced metabolites coincided with production of the manganese-dependent peroxidases and mineralization of TNT was not observed until the lignin peroxidases were detected.

Basidiomycota↗
PubMed1977

Perforated duodenal ulcer and pneumomediastinum.

Two cases of anterior wall perforation of a duodenal ulcer, resulting in pneumomediastinum and pneumoperitoneum, are presented. The literature regarding perforation of the gastrointestinal tract with associated mediastinal emphysema is reviewed.

Adult↗