The re-assimilation of ammonia produced by photorespiration and the nitrogen economy of C3 higher plants

Photorespiration involves the conversion of glycine to serine with the release of ammonia and CO₂. In C₃ terrestrial higher plants the flux through glycine and serine is so large that it results in the production of ammonia at a rate far exceeding that from reduction of new nitrogen entering the plant. The photorespiratory nitrogen cycle re-assimilates this ammonia using the enzymes glutamine synthetase and glutamine:2-oxoglutarateaminotransferase.