Alterations in Enzyme Activities in Leaves after Exposure of Plectranthus Sp. Plants to 900 mhz elec
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ELECTROMAGNETICFIELDSandELF
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Fig. 2. Alterations in NADP-ICDH activity in Plectranthus leaves after 1 hour exposure to 900 MHz radiation. The pentose phosphate pathway (PPP) is a cytosolic meta- bolic pathway that serves to generate NADPH and the syn- thesis of pentose (5-carbon) sugars and supplies reducing energy to cells. This pathway is an alternative to glycolysis. Glucose-6-phosphate dehydrogenase (G6PD) is a cytosolic enzyme in the PPP. In higher plants, several isoforms of BIOTECHNOL. & BIOTECHNOL. EQ. 23/2009/2 XI ANNIVERSARY SCIENTIFIC CONFERENCE SPECIAL EDITION/ONLINE 120 YEARS OF ACADEMIC EDUCATION IN BIOLOGY 45 YEARS FACULTY OF BIOLOGY 613 G6PDH have been reported, which are localized in the cyto- sol, the plastidic stroma, and peroxisomes. G6PDH, the rate-limiting enzyme of PPP, determines the amount of NADPH by controlling the metabolism of glucose via the PPP. It is found that G6PDH played a role in against oxidative stress in human erythrocytes that lack any other NADPH-producing route. Recent results have demonstrated that this enzyme also plays a protective role against ROS in nucleated eucaryotic cells that possess alternative routes for the production of NADPH. Using G6PDH-deficient cell lines it is showed that other sources of NADPH do not adequately replace the lack of NADPH production by G6PDH. That is, the G6PDH-deficient cells were highly sensitive to oxidative stress compared with cells expressing endogenous levels of G6PDH. Furthermore, human hepatoma cells and yeast containing high expression of G6PDH are resistant to oxidative stress. In animal cells, G6PDH expression is enhanced by oxidative stress by induced drugs that either increase the intracellular concentration of active oxygen species (AOS) or decrease the glutathione (GSH) pool. Yu et al. showed that G6PDH activation is inversely correlated to GSH intracellular levels. Тhe cellular GSH or GSSG possess roles in the regulation of defense-related gene expression in plant cells. The simultaneous increase in G6PDH activity resulted from decreased GSH pool rather than AOS production (21). Exposure of Plectranthus plants to 900 MHz EMF for 1 hour decreases G6PDH activity immediately after exposure and 2 hours later (Fig.3). It is higher at 1 st and 24 th hour after the treatment. tải về 0.92 Mb. Chia sẻ với bạn bè của bạn:
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