Higher plant NADP+-dependent isocitrate dehydrogenases, ammonium assimilation and NADPH production

The assimilation of ammonium into glutamate is mainly achieved by the GS/GOGAT pathway and 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. NADP+-dependent isocitrate dehydrogenases can carry out this function and the recent efforts concentrated on evaluating the involvement of different isoforms, distinguished by their subcellular localisation, are analysed. Furthermore, a possible role for these enzymes in the production of NADPH for redox-regulated cell metabolism, such as the recycling of glutathione required in response to oxidative stress will be discussed.