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1.
A mono-oxygenase catalysing the conversion of 2-ethyl-4-thioisonicotinamide (ethionamide) into its sulphoxide was purified from guinea-pig liver homogenates. The enzyme required stoicheiometric amounts of oxygen and NADPH for the sulphoxidation reaction. The purified protein is homogeneous by electrophoretic, antigenic and chromatographic criteria. The enzyme has mol.wt. 85000 and it contains 1g-atom of iron and 1mol of FAD per mol, but not cytochrome P-450. The enzyme shows maximal activity at pH7.4 in a number of different buffer systems and the K(m) values calculated for the substrate and NADPH are 6.5x10(-5)m and 2.8x10(-5)m respectively. The activation energy of the reaction was calculated to be 36kJ/mol. Under optimal conditions, the molecular activity of the enzyme (mol of substrate oxidized/min per mol of enzyme) is calculated to be 2.1. The oxygenase belongs to the class of general drug-metabolizing enzymes and it may act on different compounds which can undergo sulphoxidation. The mechanism of sulphoxidation was shown to be mediated by superoxide anions. 相似文献
2.
Sulphoxidation of compounds capable of undergoing biological sulphoxidation has been demonstrated in a model system (NADH-phenazine methosulphate-O(2)), known to generate superoxide anions (O(2) (-)). Addition of superoxide dismutase to this system results in complete inhibition, suggesting the involvement of O(2) (-) in sulphoxidation. 相似文献
3.
4.
Earlier studies in our laboratory demonstrated the beneficial role of Se inVigna radiata, a Se-deficient legume, during germination, as reflected in growth-related parameters and specific uptake of75Se. Uptake of Na2 75SeO3, added in vitro by mitochondria isolated from seedlings germinated in control (without Se), and Se-supplemented groups (0.5, 1.0, and 2.0 ppm Se) indicated a proportional increase in the uptake with added Na2 75SeO3, in concentrations up to 25 γM. The uptake of75Se, increased linearly with time up to 15 min and a definite efflux followed at 30 min. The results were indicative of cooperative effects during Se transport. Kinetic analyses of the uptake of75Se during time intervals of 15 and 30 min were carried out both in the whole mitochondria and the mitochondrial protein fractions. Graphical analyses using Lineweaver-Burk plot, Hill plot, log [v] vs log [A] and Scatchard plot confirmed the existence of negative cooperativity during75Se uptake. Hill coefficient (nH) values were estimated to be around 0.7–0.8. Scatchard plots for75Se uptake were biphasic, suggesting the probable presence of two classes of binding sites. The number of high and low affinity binding sites were estimated to be around 4–7 and 26–30 nmol/mg protein, respectively. Studies with mitochondrial respiratory inhibitors indicated about 10–20% of the total75Se uptake to be energy dependent. Inhibition of75Se uptake by about 60–70% by sulfate and sulfite (5–25 γM) implies the involvement of dicarboxylate port in Se transport. A decrease in the uptake of75Se by 40–60% effected by CdCl2, HgCl2, mersalyl, and NEM confirmed the interaction of thiols in the process. Evidence for the regulatory nature of75Se uptake by mitochondria ofV. radiata emerges from the present study. 相似文献
5.
The metabolic significance of Se in plants is not well documented, though the presence of many selenoenzymes in bacteria and
the essentiality of Se in higher animals is established. Since germination is an active process in plant growth and metabolism,
the effect of Se was investigated in germinatingVigna radiata L, a nonaccumulating Sedeficient legume. Growth and protein were enhanced in seedlings supplemented with selenium (Se) as
sodium selenite in the medium up to 1 μg/mL. The pattern of uptake of75Se in the differentiating tissues and the subcellular distribution were investigated. The percentage of incorporation of75Se was greater in the mitochondria at the lowest level (0.5 μg/mL) of Se supplementation compared to higher levels of Se exposure.
Proteins precipitated from the postmitochondrial supernatant fractions, when separated by means of polyacrylamide gel electrophoresis
(PAGE), indicated a major selenoprotein in the seedlings germinated at 2.0 μg/mL Se. In seedlings grown with supplemented
Se, enhanced respiratory control ratio and succinate dehydrogenase activity were observed in the mitochondria of tissues,
indicative of a role for Se in mitochondrial membrane functions. 相似文献
6.
Megha Kaushik Chen Yu Wang Michael H. Barnett Raymond Garrick John Parratt Stuart L. Graham Prema Sriram Con Yiannikas Alexandr Klistorner 《PloS one》2013,8(10)
Aim
To examine the relationship between retinal ganglion cell loss and changes in the inner nuclear layer (INL) in optic neuritis (ON).Methods
36 multiple sclerosis (MS) patients with a history of ON and 36 age and sex-matched controls underwent Optical Coherence Tomography. The paramacular retinal nerve fiber layer (RNFL), combined ganglion cell and inner plexiform layers (GCL/IPL) and inner nuclear layer (INL) thickness were measured at 36 points around the fovea. To remove inter-subject variability, the difference in thickness of each layer between the ON and fellow eye of each patient was calculated. A topographic analysis was conducted.Results
The INL of the ON patients was thicker than the controls (42.9µm versus 39.6µm, p=0.002). ON patients also had a thinner RNFL (27.8µm versus 32.2µm, p<0.001) and GCL/IPL (69.3µm versus 98.1µm, p<0.001). Among the controls, there was no correlation between RNFL and GCL/IPL as well as RNFL and INL, but a positive correlation was seen between GCL/IPL and INL (r=0.65, p<0.001). In the ON group, there was a positive correlation between RNFL and GCL/IPL (r=0.80, p<0.001) but a negative correlation between RNFL and INL (r=-0.61, p<0.001) as well as GCL/IPL and INL (r=-0.44, p=0.007). The negative correlation between GCL/IPL and INL strengthened in the ON group when inter-subject variability was removed (r=-0.75, p<0.001). Microcysts within the INL were present in 5 ON patients, mainly in the superior and infero-nasal paramacular regions. While patients with microcysts lay at the far end of the correlation curve between GCL/IPL and INL (i.e. larger INL and smaller GCL/IPL compared to other patients), their exclusion did not affect the correlation (r= -0.76, p<0.001).Conclusions
INL enlargement in MS-related ON is associated with the severity of GCL loss. This is a continuous relationship and patients with INL microcysts may represent the extreme end of the scale. 相似文献7.
ABSTRACT:?Xylanases are hydrolases depolymerizing the plant cell wall component xylan, the second most abundant polysaccharide. The molecular structure and hydrolytic pattern of xylanases have been reported extensively and the mechanism of hydrolysis has also been proposed. There are several models for the gene regulation of which this article could add to the wealth of knowledge. Future work on the application of these enzymes in the paper and pulp, food industry, in environmental science, that is, bio-fueling, effluent treatment, and agro-waste treatment, etc. require a complete understanding of the functional and genetic significance of the xylanases. However, the thrust area has been identified as the paper and pulp industry. The major problem in the field of paper bleaching is the removal of lignin and its derivatives, which are linked to cellulose and xylan. Xylanases are more suitable in the paper and pulp industry than lignin-degrading systems. 相似文献
8.
Prema Kurien 《Ethnic and racial studies》2013,36(2):263-293
This article focuses on the political struggles between Hindu and Muslim Indian immigrant groups in the United States over the definition of "Indianness". Hindu Indian American organizations define India as a Hindu society and are strong supporters of the Hindu nationalist movement in India. Muslim Indian American organizations, on the other hand, view India as a multi-religious and multicultural society. They are striving to safeguard India's secularism and towards this end, have entered into coalitional relationships with lower caste groups. Both types of organizations are working to influence American and Indian politics in line with their respective interests, leading to an exacerbation of the conflict between the two immigrant groups. This article examines the reasons for this development and its implications, both for the development of an Indian American community in the United States and for religion and politics in India. 相似文献
9.
Inactivation of nitrate reductase alters metabolic branching of carbohydrate fermentation in the cyanobacterium Synechococcus sp. strain PCC 7002
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10.
Multiple mechanisms for Pitx-1 transactivation of a luteinizing hormone beta subunit gene 总被引:1,自引:0,他引:1
Melamed P Koh M Preklathan P Bei L Hew C 《The Journal of biological chemistry》2002,277(29):26200-26207