Enzyme redundancy and the importance of 2-oxoglutarate in plant ammonium assimilation.
Ammonium is the reduced nitrogen form available to plants for assimilation into amino acids. This is achieved by the GS/GOGAT pathway that requires carbon skeletons in the form of 2-oxoglutarate. To date, the exact enzymatic origin of this organic acid for plant ammonium assimilation is unknown. Isocitrate dehydrogenases and aspartate aminotransferases have been proposed to carry out this function. Since different (iso)forms located in several subcellular compartments are present within a plant cell, recent efforts have concentrated on evaluating the involvement of these enzymes in ammonium assimilation. Furthermore, several observations indicate that 2-oxoglutarate is a good candidate as a metabolic signal to regulate the co-ordination of C and N metabolism. This will be discussed with respect to recent advances in bacterial signalling processes involving a 2-oxoglutarate binding protein called PII.
Hodges
Michael
M
Institut de Biotechnologie des Plantes, CNRS UMR8618, Université Paris Sud-XI, 91405 Orsay Cedex, France. hodges@ibp.u-psud.fr
D000594:Amino Acid Oxidoreductases / Q000378:metabolism; D001219:Aspartate Aminotransferases / Q000378:metabolism; D002244:Carbon / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology; D004798:Enzymes / Q000378:metabolism*; D050790:Glutamate Synthase (NADH); D018698:Glutamic Acid / Q000096:biosynthesis; D007521:Isocitrate Dehydrogenase / Q000378:metabolism; D007656:Ketoglutaric Acids / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology; D009584:Nitrogen / Q000378:metabolism; D010944:Plants / Q000201:enzymology*; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D015398:Signal Transduction
D004798:Enzymes; D007656:Ketoglutaric Acids; D000644:Quaternary Ammonium Compounds; D018698:Glutamic Acid; D002244:Carbon; D007521:Isocitrate Dehydrogenase; D000594:Amino Acid Oxidoreductases; D050790:Glutamate Synthase (NADH); C042233:glutamate synthase (ferredoxin); D001219:Aspartate Aminotransferases; D009584:Nitrogen