Glutamate synthase: a complex iron-sulfur flavoprotein

Glutamate synthase is a complex iron-sulfur flavoprotein that forms L-gluta mate from L-glutamine and 2-oxoglutarate. It participates with glutamine sy nthetase in ammonia assimilation processes. The known structural and bioche mical properties of glutamate synthase from Azospirillum br brasilense, a n itrogen-fixing bacterium, will be discussed in comparison to those of the f erredoxin-dependent enzyme from photosynthetic tissues and of the eukaryoti c reduced pyridine nucleotide-dependent form of glutamate synthase in order to gain insight into the mechanism of the glutamate synthase reaction. Seq uence analyses also revealed that the small subunit of bacterial glutamate synthase may be the prototype of a novel class of flavin adenine dinucleoti de- and iron-sulfur-containing oxidoreductase widely used as an enzyme subu nit or domain to transfer reducing equivalents from NAD(P)H to an acceptor protein or protein domain.