Involved in glutamate biosynthesis in leaf. Required for the reassimilation of ammonium ions generated during photorespiration. 2 L-glutamate + 2 oxidized [2Fe-2S]-[ferredoxin] = 2-oxoglutarate + 2 H(+) + L-glutamine + 2 reduced [2Fe-2S]-[ferredoxin] Binds 1 [3Fe-4S] cluster. Amino-acid biosynthesis; L-glutamate biosynthesis via GLT pathway; L-glutamate from 2-oxoglutarate and L-glutamine (ferredoxin route): step 1/1. Energy metabolism; nitrogen metabolism. Interacts with SHM1. Dual targeting is supposed to depend on alternative initiation: MET-1 or MET-3 for chloroplast or mitochondrion location, respectively. Highly expressed in leaves. High expression in the leaf mesophyll and phloem companion cell-sieve element complex. Up-regulated by GATA21/GNC and GATA22/CGA1. Induced by light or sucrose. Displays photorespiratory chlorosis when grown at ambient CO2. May be due to an intron retention. Belongs to the glutamate synthase family.