Elevated glutamate dehydrogenase flux in glucose-deprived hybridoma and myeloma cells: Evidence from 1H/15N NMR
✍ Scribed by Kristina Martinelle; Magnus Doverskog; Ulla Jacobsson; Bogdan E. Chapman; Philip W. Kuchel; Lena Häggström
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 160 KB
- Volume
- 60
- Category
- Article
- ISSN
- 0006-3592
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✦ Synopsis
The glutamine metabolism was studied in glucose-starved and glucose-sufficient hybridoma and Sp2/ 0-Ag14 myeloma cells. Glucose starvation was attained by cultivating the hybridoma cells with fructose instead of glucose, and the myeloma cells with a low initial glucose concentration which was rapidly exhausted. Glutamine used in the experiments was labeled with 15 N, either in the amine or in the amide position. The fate of the label was monitored by 1 H/ 15 N NMR analysis of released 15 NH + 4 and 15 N-alanine. Thus, NH + 4 formed via glutaminase (GLNase) could be distinguished from NH + 4 formed via glutamate dehydrogenase (GDH). In the glucose-sufficient cells a small but measurable amount of 15 NH + 4 released by GDH could be detected in both cell lines (0.75 and 0.31 µmole/10 6 cells for hybridoma and myeloma cells, respectively). The uptake of glutamine and the total production of NH + 4 was significantly increased in both fructose-grown hybridoma and glucosestarved myeloma cells, as compared to the glucosesufficient cells. The increased NH + 4 production was due to an increased throughput via GLNase (1.6 -1.9-fold in the hybridoma, and 2.7-fold in the myeloma cell line) and an even further increased metabolism via GDH (4.8-7.9-fold in the hybridoma cells, and 3.1-fold in the myeloma cells). The data indicate that both GLNase and GDH are down-regulated when glucose is in excess, but upregulated in glucose-starved cells. It was calculated that the maximum potential ATP production from glutamine could increase by 35-40 % in the fructose-grown hybridoma cells, mainly due to the increased metabolism via GDH.