| Primary Identifier | IPR012075 | Type | Family |
| Short Name | Glu_synth_lsu_1/3 |
| description | The large (alpha, GltB) subunit of bacterial glutamate synthase (GOGAT) consists of three domains: N-terminal domain (amidotransferase domain ), central (consisting of and the FMN-binding domain ), and C-terminal domain. This family of sequences represent a fusion of the N-terminal (amidotransferase) domain and the C-terminal structural domain.The stand-alone forms of the three domains (and for domains 1 and 2), as well as partial fusions, occur in the archaeal type of GOGAT, where the large subunit is represented by three separate proteins, corresponding to the three domains of the "standard"bacterial enzyme [].Originally, only the ORF encoding the central domain of GOGAT has been recognised and annotated as GltB in archaea, and the rest of the large subunit was thought to be missing, which may lead to some miss-annotations []. This has led to speculations that the archaeal form of the GOGAT large subunit is the ancestral minimum form of the enzyme. Later analysis showed, however, that in all archaea where the large subunit has been found, its entire sequence is represented by three separate ORFs [].Glutamate synthase is a complex iron-sulphur flavoprotein that catalyses the reductive synthesis of L-glutamate from 2-oxoglutarate and L-glutamine via intramolecular channelling of ammonia, a reaction in the bacterial, yeast and plant pathways for ammonia assimilation []. GOGAT is a multifunctional enzyme that performs L-glutamine hydrolysis, conversion of 2-oxoglutarate into L-glutamate, and electron uptake from an electron donor [].There are four classes of GOGAT [, ]: 1. Bacterial NADPH-dependent GOGAT (NADPH-GOGAT, ). This standard bacterial NADPH-GOGAT is composed of a large subunit and a small subunit.2. Ferredoxin-dependent form in cyanobacteria and plants (Fd-GOGAT, ) displays a single-subunit structure corresponding to the large bacterial subunit.3. Pyridine-linked form in both photosynthetic and nonphotosynthetic eukaryotes (eukaryotic GOGAT or NADH-GOGAT, ) displays a single-subunit structure corresponding to the fusion of the small and the large bacterial subunits ().4. The archaeal type with stand-alone proteins corresponding to the N-terminal, FMN-binding, and the C-terminal domains of the large subunit [, ](, ), and to the small subunit. |
