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Synthesis of glutamate by mitochondria – An anaplerotic function for glutamate dehydrogenase
Author(s) -
Yamaya Tomoyuki,
Oaks Ann
Publication year - 1987
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1987.tb04334.x
Subject(s) - photorespiration , glutamate dehydrogenase , glycine , glutamate receptor , biochemistry , glutamine , citric acid cycle , mitochondrion , glutamate synthase , amino acid , glutamine synthetase , serine , biology , metabolism , enzyme , receptor
The photorespiratory nitrogen cycle was initially thought to be a closed cyclic process. If this were true the loss of glutamate, glutamine, serine or glycine to other processes, such as protein synthesis or export from the leaves, would not be possible in a stoichiometric sense. However, recent studies with [ 15 N]‐labeled amino acids show that there are alternative sources of nitrogen for photorespiration, indicating that the nitrogen cycle is not a closed cyclic system. In addition recent work with 15 NH 4 Cl and [ 15 N]‐glycine and a metabolically competent mitochondria system has shown that glutamate is synthesized in the mitochondria. Hence the glutamate dehydrogenase (GDH, EC 1.4.1.2) in mitochondria could also be active in the reassimilation of NH 4 . We would like to propose that one function of mitochondrial GDH is to synthesize glutamate from some of the NH 4 released by photorespiration and that this glutamate represents a reserve for use in biosynthetic reactions.