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 [15N]‐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 15NH4Cl and [15N]‐glycine and a metabolically competent mitochondria system has shown that glutamate is synthesized in the mitochondria. Hence the glutamate dehydrogenase (GDH, EC 22.214.171.124) in mitochondria could also be active in the reassimilation of NH4. We would like to propose that one function of mitochondrial GDH is to synthesize glutamate from some of the NH4 released by photorespiration and that this glutamate represents a reserve for use in biosynthetic reactions.
|Number of pages||8|
|Publication status||Published - 1987 Aug|
- Nitrogen metabolism
- photorespiratory nitrogen cycle
ASJC Scopus subject areas
- Plant Science
- Cell Biology