Physiology of induced catalase synthesis in Rhodopseudomonas spheroides

Clayton, Roderick K.

doi:10.1002/jcp.1030550102

Cited by 21 publications

(5 citation statements)

References 8 publications

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“…Rhodobacter sphaeroides f. sp. denitrificans was grown at 30 °C in Hutner medium (13) under aerobic conditions (1.5 L of culture in 3 L Erlenmeyer flask, 150 rpm). E. coli strains were grown at 37 °C in Luria-Bertani medium.…”

Section: Methodsmentioning

confidence: 99%

Access to the Active Site of Periplasmic Nitrate Reductase: Insights from Site-Directed Mutagenesis and Zinc Inhibition Studies

et al. 2007

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The periplasmic nitrate reductase (NapAB), a member of the DMSO reductase superfamily, catalyzes the first step of the denitrification process in bacteria. In this heterodimer, a di-heme NapB subunit is associated to the catalytic NapA subunit that binds a [4Fe-4S] cluster and a bis(molybdopterin guanine dinucleotide) cofactor. Here, we report the kinetic characterization of purified mutated heterodimers from Rhodobacter sphaeroides. By combining site-directed mutagenesis, redox potentiometry, EPR spectroscopy, and enzymatic characterization, we investigate the catalytic role of two conserved residues (M153 and R392) located in the vicinity of the molybdenum active site. We demonstrate that M153 and R392 are involved in nitrate binding: the Vm measured on the M153A and R392A mutants are similar to that measured on the wild-type enzyme, whereas the Km for nitrate is increased 10-fold and 200-fold, respectively. The use of an alternative enzymatic assay led us to discover that NapAB is uncompetitively inhibited by Zn2+ ions (Ki' = 1 microM). We used this property to further probe the active site access in the mutant enzymes. It is proposed that R392 acts as a filter by preventing a direct reduction of the Mo atom by small reducing molecules and partially protecting the active site against zinc inhibition. In addition, we show that M153 is a key residue mediating this inhibition likely by coordinating Zn2+ ions via its sulfur atom. This residue is not conserved in the DMSO reductase superfamily while it is conserved in the periplasmic nitrate reductase family. Zinc inhibition is therefore likely to be specific and restricted to periplasmic nitrate reductases.

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Section: Methodsmentioning

confidence: 99%

Access to the Active Site of Periplasmic Nitrate Reductase: Insights from Site-Directed Mutagenesis and Zinc Inhibition Studies

et al. 2007

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“…In-creased activities of SOD [52-541, catalase [55][56][57] and glutathione peroxidase [58] have been observed following exposured to redox-cycling compounds. In-creased activities of SOD [52-541, catalase [55][56][57] and glutathione peroxidase [58] have been observed following exposured to redox-cycling compounds.…”

Section: In Vivo Methodologiesmentioning

confidence: 99%

“…Antioxidant enzyme activities, As mentioned previously, SOD, catalase and glutathione peroxidase protect organisms from oxidative damage by the removal of partially reduced oxygen species. In-creased activities of SOD [52-541, catalase [55][56][57] and glutathione peroxidase [58] have been observed following exposured to redox-cycling compounds.…”

Section: In Vivo Methodologiesmentioning

confidence: 99%

Biochemical Responses in Aquatic Animals: A Review of Determinants of Oxidative Stress

Giulio

Washburn

Wenning

et al. 1989

Environ Toxicol Chem

435

111

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The study of biochemical responses in aquatic animals comprises a vigorous area of inquiry within ecotoxicology for a number of reasons, including the perceived need for basic research in the field, the desire for highly sensitive biomarkers useful for biomonitoring and the particular concern for elevated rates of neoplasia observed in some aquatic systems. In this paper, an approach only recently investigated by aquatic toxicologists will be described and reviewed in detail. This approach is based on theories of oxyradical generation and subsequent oxidative stress in biological systems. Of particular concern to environmental toxicologists with respect to these phenomena are the abilities of a number of common and diverse compounds to undergo enzymatically facilitated redox cycling in cells and thereby generate oxyradicals under aerobic conditions. Mechanisms of oxyradical generation, toxicological consequences of these processes and endogenous antioxidant defense systems are described. In addition, methodologies for studying these phenomena are discussed and recent studies demonstrating their applicability to aquatic toxicology are reviewed.

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“…Houseflies, cockroaches and Khapra beetles, but not milkweed bugs, selectively absorb cholesterol and campesterol, in preference to sitosterol, from their diets (1)(2)(3)(4). A much larger number of other phytophagous and omnivorous insects were shown to remove methyl and ethyl groups from C24 in the side chains of plant and fungal sterols by a selective dealkylation process and reduce the A 24 or A 22,24 intermediates of this process to cholesterol (5-10).…”

Section: Introductionmentioning

confidence: 99%

Selective uptake and lack of dealkylation of phytosterols by cactophilic species ofDrosophila

Kircher

Rosenstein

Fogleman

1984

Lipids

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The selective absorption of cholesterol and campesterol and discrimination against sitosterol was demonstrated withDrosophila mojavensis andDrosophila nigrospiracula, using a synthetic medium and 2 natural host cacti. Preferential absorption of trace amounts of phytosterols from a large quantity of other lipids occurred whenD. arizonensis andD. mojavensis were reared from agria cactus. The absence of dealkylation of sitosterol to cholesterol was demonstrated withD. mojavensis andD. mettleri, reared on a sterol‐deficient medium supplemented with sitosterol.

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Physiology of induced catalase synthesis in Rhodopseudomonas spheroides

Cited by 21 publications

References 8 publications

Access to the Active Site of Periplasmic Nitrate Reductase: Insights from Site-Directed Mutagenesis and Zinc Inhibition Studies

Access to the Active Site of Periplasmic Nitrate Reductase: Insights from Site-Directed Mutagenesis and Zinc Inhibition Studies

Biochemical Responses in Aquatic Animals: A Review of Determinants of Oxidative Stress

Selective uptake and lack of dealkylation of phytosterols by cactophilic species ofDrosophila

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