1.1. Ferredoxin-glutamate synthase from the green alga Chlamydomonas reinhardii appears to contain as prosthetic groups, 1 FAD, 1 FMN and 1 |3Fe-xS | cluster, per molecule of Mr = 146,000.2.2. The synthesis of glutamate, catalyzed by this enzyme, proceeds through the formation of an enzyme-bound free radical of flavin semiquinone.3.3. This enzyme may catalyze the ferredoxin-dependent reduction of 2-oxoglutarate, in the absence of glutamine.