| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
- Nordman, Tomas, et al.
(författare)
-
Regeneration of the antioxidant ubiquinol by lipoamide dehydrogenase, thioredoxin reductase and glutathione reductase
- 2003
-
Ingår i: Biofactors. - : IOS Press. - 0951-6433 .- 1872-8081. ; 18:1-4, s. 45-50
-
Tidskriftsartikel (refereegranskat)abstract
- Ubiquinol is a powerful antioxidant, which is oxidized in action and needs to be replaced or regenerated to be capable of a sustained effort. This article summarises current knowledge of extramitochondrial reduction of ubiquinone by three flavoenzymes, i.e. lipoamide dehydrogenase, glutathione reductase and thioredoxin reductase, belonging to the same pyridine nucleotide-disulfide oxidoreductase family. These three enzymes are the most efficient extramitochondrial ubiquinone reductases so far described. The reduction of ubiquinone by lipoamide dehydrogenase and glutathione reductase is potently stimulated by zinc and the highest rate of reduction is achieved at acidic pH and the rates are equal with either NADPH or NADH as co-factors. The most efficient ubiquinone reductases are mammalian cytosolic thioredoxin reductases, which are selenoenzymes with a number of biological functions. Reduction of ubiquinone by thioredoxin reductase is in contrast to the other two enzymes investigated, inhibited by zinc and shows a sharp physiological pH optimum at pH 7.5. Furthermore, the reaction is selenium dependent as revealed from experiments using truncated and mutant forms of the enzyme and also in a cellular context by selenium treatment of transfected thioredoxin reductase overexpressing stable cell lines. The reduction of ubiquinone by the three enzymes offers a multifunctional system for extramitochondrial regeneration of an important antioxidant.
|
|
| 5. |
- Rönner, Anna-Clara, 1971, et al.
(författare)
-
Species identification by genotyping and determination of antibiotic resistance in Campylobacter jejuni and Campylobacter coli from humans and chickens in Sweden.
- 2004
-
Ingår i: International journal of food microbiology. - : Elsevier BV. - 0168-1605 .- 1879-3460. ; 96:2, s. 173-9
-
Tidskriftsartikel (refereegranskat)abstract
- Campylobacter is today the most common cause of human bacterial enteritis in Sweden, as well as in most other industrialized countries. Common sources of infection are undercooked chicken meat, unpasteurized milk and contaminated drinking water. One aim with our present study was to identify the species Campylobacter jejuni and Campylobacter coli strains from humans and chickens using a polymerase chain reaction/restriction enzyme analysis (PCR/REA) method, as well as traditional hippurate hydrolysis test. Another aim was to investigate the antibiotic resistance pattern of the human domestic C. jejuni/C. coli isolates from infected patients and isolates from healthy Swedish chicken, as well as isolates from humans infected abroad. If discrimination between C. jejuni and C. coli was based on testing for hippurate hydrolysis, 95% of the human domestic strains and 88% of the chicken strains were identified as C. jejuni. Based on genotyping by PCR/REA, 100% of the human domestic strains and 98% of the chicken strains were attributed to C. jejuni. The E-test and disc diffusion methods were used for phenotypic antibiotic resistance studies. The two methods gave similar results. Most Swedish C. jejuni/C. coli isolates both from humans and chickens were sensitive to doxycycline and erythromycin, which are antibiotics used to treat human infection. Only 7% of the human domestic strains and 2% of the chicken strains were resistant to the quinolones tested. As a comparison, more than 94% of strains isolated from travelers to Asia and southern Europe showed antibiotic resistance to one or more drugs.
|
|
| 6. |
- Xia, Ling, et al.
(författare)
-
The mammalian cytosolic selenoenzyme thioredoxin reductase reduces ubiquinone. A novel mechanism for defense against oxidative stress
- 2003
-
Ingår i: Journal of Biological Chemistry. - : American Society for Biochemistry and Molecular Biology. - 0021-9258 .- 1083-351X. ; 278:4, s. 2141-2146
-
Tidskriftsartikel (refereegranskat)abstract
- The selenoprotein thioredoxin reductase (TrxR1) is an essential antioxidant enzyme known to reduce many compounds in addition to thioredoxin, its principle protein substrate. Here we found that TrxR1 reduced ubiquinone-10 and thereby regenerated the antioxidant ubiquinol-10 (Q10), which is important for protection against lipid and protein peroxidation. The reduction was time- and dose-dependent, with an apparent K(m) of 22 microm and a maximal rate of about 12 nmol of reduced Q10 per milligram of TrxR1 per minute. TrxR1 reduced ubiquinone maximally at a physiological pH of 7.5 at similar rates using either NADPH or NADH as cofactors. The reduction of Q10 by mammalian TrxR1 was selenium dependent as revealed by comparison with Escherichia coli TrxR or selenium-deprived mutant and truncated mammalian TrxR forms. In addition, the rate of reduction of ubiquinone was significantly higher in homogenates from human embryo kidney 293 cells stably overexpressing thioredoxin reductase and was induced along with increasing cytosolic TrxR activity after the addition of selenite to the culture medium. These data demonstrate that the selenoenzyme thioredoxin reductase is an important selenium-dependent ubiquinone reductase and can explain how selenium and ubiquinone, by a combined action, may protect the cell from oxidative damage.
|
|
