Previous papers in this series have reported the hypoxanthinedependent oxidation of sulfite by cyanide-inhibited xanthine oxidase (1) and experiments which permitted postulation of the structure of the active site of this enzyme (2). In the present study, xanthine oxidase acting on its substrates has been found to initiate the aerobic oxidation of sulfite by free radical chains of great length ...

We studied the kinetics of reactions of cob(I)alamin and cob(I)inamide with thiosulfate, sulfite, and dithionite by UV-Visible (UV-Vis) and stopped-flow spectroscopy. We found that the two Co(I) species were oxidized by these sulfur-containing compounds to Co(II) forms: oxidation by excess thiosulfate leads to penta-coordinate complexes and oxidation by excess sulfite or dithionite leads to hex...

A reduced nicotinamide adenine dinucleotide phosphate (NADPH)-specific enzyme from Escherichiu wti, isolated as a nitrite reductase, catalyzed the reductions of both nitrite and hydroxylamine to ammonia, and the ratio of the two activities remained constant during partial purification (1). The demonstration in the same species of an NADPH-specific enzyme catalyzing the reductions of hydroxylami...

Transposon Tn5 insertions causing anaerobic cysteine auxotrophy were isolated from a Salmonella typhimurium cysI parent (auxotrophic under aerobic but not anaerobic conditions). Insertions in one mutant group appeared to be in cysG. A second group of insertions, designated asr (anaerobic sulfite reduction), were located near map unit 53 on the S. typhimurium chromosome. They did not cause aerob...

An enzyme electrode was developed using the enzyme sulfite oxidase (EC1.8.3.1) immobilized onto pig intestine. Hydrogen peroxide produced was monitored amperometrically. All experimental parameters such as pH, temperature, buffer constituent concentration, were thoroughly investigated and optimized when appropriate. The response to sulfite concentration was linear in the range 5.2´...

A patient suffering from a combined deficiency of sulfite oxidase (sulfite dehydrogenase; sulfite:ferricytochrome c oxidoreductase, EC 1.8.2.1) and xanthine dehydrogenase (xanthine:NAD+ oxidoreductase, EC 1.2.1.37) is described. The patient displays severe neurological abnormalities, dislocated ocular lenses, and mental retardation. Urinary excretion of sulfite, thiosulfate, S-sulfocysteine, ta...

The aim of the present study is to detect the monodehydroascorbic acid (MDA) radical in broad bean (Vicia faba L.) leaves which were treated by vacuum-infiltration in Na2SO3 solution and subsequent centrifugation (sulfitetreated leaves). When sulfite-treated leaves were illuminated with white light, the electron spin resonance (ESR) signal of MDA radical was observed. The level of the MDA radic...

NrfA is a pentahaem cytochrome present in a wide-range of γ-, δ- and ε-proteobacteria. Its nitrite and nitric oxide reductase activities have been studied extensively and contribute to respiratory nitrite ammonification and nitric oxide detoxification respectively. Sulfite is a third substrate for NrfA that may be encountered in the micro-oxic environments where nrfA is expressed. Consequently,...

Plant sulfite oxidase [SO; E.C.1.8.3.1] has been shown to be a key player in protecting plants against exogenous toxic sulfite. Recently we showed that SO activity is essential to cope with rising dark-induced endogenous sulfite levels in tomato plants (Lycopersicon esculentum/Solanum lycopersicum Mill. cv. Rheinlands Ruhm). Here we uncover the ramifications of SO impairment on carbon, nitrogen...

Azoxybacilin, produced by Bacillus cereus, has a broad spectrum of antifungal activity in methionine-free medium and has been suggested to inhibit sulfite fixation. We have further investigated the mode of action by which azoxybacilin kills fungi. The compound inhibited the incorporation of [35S] sulfate into acid-insoluble fractions of Saccharomyces cerevisiae under conditions in which virtual...