Robinson, S. A.; (1990) Glutamate and glutamine metabolism in carrot cell culture. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The objective of the work described in this thesis was to investigate the metabolism of glutamine and glutamate in carrot cell suspension cultures and in particular to focus on the role of the enzyme glutamate dehydrogenase in plant nitrogen metabolism. Experiments using in vivo nuclear magnetic resonance spectroscopy, in vitro gas chromatography- mass spectrometry and automated 15N/13C mass spectrometry have been used, in association with physiological studies, to demonstrate that glutamate dehydrogenase is active in the oxidation of glutamate, but not in the reductive amination of 2-oxoglutarate. These studies of nitrogen metabolism in cell suspension cultures of carrot (Daucus carota L. cv Chantenay) have yielded results consistent with the primary assimilation of ammonium occuring via the glutamate synthase pathway. The results show that glutamate dehydrogenase is derepressed under conditions of carbon limitation and are consistent with observations in other plant tissues, particularly roots and senescing organs. The evidence suggests that the function of glutamate dehydrogenase is the oxidation of glutamate, thus ensuring sufficient carbon skeletons for effective functioning of the TCA cycle. This catabolic role for glutamate dehydrogenase implies an important regulatory function in carbon and nitrogen metabolism.

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