60. Experiments were carried out in cultured cells to determine onship between g
ID: 253711 • Letter: 6
Question
60. Experiments were carried out in cultured cells to determine onship between glucose-6-phosphate dehydrogenase ) activity and rates of cell growth. Cells were cultured in m supplemented with serum, which contains growth fac tors that stimulate G6PDH activity. Predict how the cellular (G6PDH NADPH/NAD P ratio would change under the following cir- cumstances: (a) Serum is withdrawn from the medium. (b) DHEA, an inhibitor of glucose-6-phosphate dehydrogenase, is added. (c) The oxidant H202 is added. (d) Serum is withdrawn and H2O2 is added.Explanation / Answer
G6PD is the rate-limiting enzyme of the pentose phosphate pathway, determines the production of NADPH by controlling the metabolism of glucose via the PPP.
1- when serum is withdrawn from the medium- Serum increases the G6PD activity in growing cell, if serum is withdrawn it will cause a decrease in the activity of G6PD and which reduces the NADPH/NADP+ ratio.
2-Dehydroepiandrosterone (DHEA) which inhibit G6PDH activity- decreases the NADPH/NADP+ ratio.
3- G6PDH protect the cell from the growth inhibitory effects of H2O2 - it has no effect on NADPH/NADP+ ratio.
4- Serum increases the G6PD activity in growing cell- as serum withdrawal reduces G6PDH activity, and when simultaneously H2O2 is provided it will reduce NADPH/NADP+ ratio.
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