Activity of glutamate dehydrogenase is increased in ammonia-stressed hybridoma cells |
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Authors: | Bonarius H P Houtman J H de Gooijer C D Tramper J Schmid G |
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Affiliation: | Department PRP-Biotechnology, Hoffmann-La Roche Ltd., Basel, Switzerland.Bona@Novo.dk |
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Abstract: | The effect of added ammonia on the intracellular fluxes in hybridoma cells was investigated by metabolic-flux balancing techniques. It was found that, in ammonia-stressed hybridoma cells, the glutamate-dehydrogenase flux is in the reverse direction compared to control cells. This demonstrates that hybridoma cells are able to prevent the accumulation of ammonia by converting ammonia and alpha-ketoglutarate into glutamate. The additional glutamate that is produced by this flux, as compared to the control culture, is converted by the reactions catalyzed by alanine aminotransferase (45% of the extra glutamate) and aspartate aminotransferase (37%), and a small amount is used for the biosynthesis of proline (6%). The remaining 12% of the extra glutamate is secreted into the culture medium. The data suggest that glutamate dehydrogenase is a potential target for metabolic engineering to prevent ammonia accumulation in high-cell-density culture. |
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