The effects of ZnCl2 additions on a mercuric reductase, merA, ammonia monooxygenase, amoA, and hydroxylamine (NH2OH) oxidoreductase, hao, gene expression were examined in continuously cultured Nitrosomonas europaea cells. The reactor was operated for 85 days with a 6.9 d hydraulic retention time and with four successive additions of ZnCl2 achieving maximum concentrations from 3 to 90 microM Zn2...

With global heavy metal contamination increasing, plants that can process heavy metals might provide efficient and ecologically sound approaches to sequestration and removal. Mercuric ion reductase, MerA, converts toxic Hg2+ to the less toxic, relatively inert metallic mercury (Hg0) The bacterial merA sequence is rich in CpG dinucleotides and has a highly skewed codon usage, both of which are p...

It is well known that the determination of ascorbic acid in urine by titration with 2,6dichlorophenol indophenol in acid solution is not a specific method. Various interfering substances have been reported, such as sulfhydryl compounds (l), thiosulfate (2), and pyridium (medication) (3). The same limitations apply to other oxidation-reduction methods, except when the reducing substance is deter...

The interaction of the flavoprotein glutathione reductase from yeast with NADH has been studied. A reduced enzyme species resulting from addition of 2 electrons per enzymebound FAD is formed on addition of NADH to oxidized enzyme. This Z-electron reduced enzyme is stable toward further reduction to the 4-electron reduced state by excess NADH. Yeast glutathione reductase reduced by excess NADH h...

NADH:cytochrome b5 reductase activates the mitomycins to alkylating intermediates in vitro. To investigate the intracellular role of this enzyme in mitomycin bioactivation, Chinese hamster ovary cell transfectants overexpressing rat NADH:cytochrome b5 reductase were generated. An NADH:cytochrome b5 reductase-transfected clone expressed 9-fold more enzyme than did parental cells; the levels of o...

The endoplasmic reticulum (ER) enzyme, 3-hydroxy-3-methylglutaryl-CoA reductase, catalyzes the production of mevalonate, a rate-controlling step in cholesterol biosynthesis. Excess sterols promote ubiquitination and subsequent degradation of reductase as part of a negative feedback regulatory mechanism. To characterize the process in more detail, we here report the development of a permeabilize...

The addition of nitrite, the product of the reaction catalysed by nitrate reductase, to cell suspensions of the yeast Hansenula anomala caused a reversible inactivation of NADPH-dependent nitrate reductase activity. The haem- and Mo-dependent and Mo-dependent activities of nitrate reductase, determined with the non-physiological electron donors FMNH2 and reduced methyl viologen respectively, we...

Reactive oxygen species are implicated as mediators of tissue damage in ischemic and toxic acute renal failure. Whereas many agents can inhibit renal ischemic injury, only hepatocyte growth factor, melatonin, N-acetylcysteine, and DMSO inhibit injury after mercuric chloride administration. Although it has been suggested that DMSO may chelate the mercuric ion, more recent studies suggest that it...

The nitrate reductase of Escherichia coli K-12 was localized in a particulate fraction of the cell and it sedimented as if it were bound to a large substructure that is subject to fragmentation during cell disruption procedures. Soluble enzyme, exhibiting a homogenous profile in sucrose gradients, was released from this fraction by an alkaline-heat treatment. Less than 1.5% of total active nitr...

Desiccation of 8- to 13-day-old seedlings, achieved by withholding nutrient solution from the vermiculite root medium, caused a reduction in nitrate reductase activity of the leaf tissue. Activity declined when leaf water potentials decreased below -2 bars and was 25% of the control at a leaf water potential of -13 bars. Experiments were conducted to determine whether the decrease in nitrate re...