| Type: | Family | Name: | Glutamate synthase, eukaryotic |
| Description: | This group represents the eukaryotic type of glutamate synthase (NADH-GOGAT, ). This pyridine-linked form is found both photosynthetic and nonphotosynthetic eukaryotes. It displays a single-subunit structure corresponding to the fusion of the small and the large bacterial subunits.Glutamate synthase (GOGAT, GltS) 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 functions through three distinct active centres carrying out multiple reaction steps: L-glutamine hydrolysis, conversion of 2-oxoglutarate into L-glutamate, and electron uptake from an electron donor []. The small subunit functions as a FAD-dependent NADPH oxidoreductase, which serves to transfer reducing equivalents to the site of glutamate synthesis on the large subunit through the enzyme [3Fe-4S]cluster (on the large subunit) and at least one of its [4Fe-4S] centres [, ]. The large subunit contains the GltS L-glutamine amidotransferase (GAT) site where L-Gln binds and is hydrolysed to yield L-Glu and ammonia. The latter is transferred through the intramolecular ammonia tunnel [] to the glutamate synthase site where 2-OG binds, is converted to the iminoglutarate (2-IG) intermediate, and reduced to L-Glu by receiving reducing equivalents from the reduced FMN cofactor at this site [].There are four classes of GOGAT [, ]: 1. Bacterial NADPH-dependent GOGAT (NADPH-GOGAT, ). This standard bacterial NADPH-GOGAT is composed of a large (alpha, GltB) subunit (, subfamily , which in turn contains three domains) and a small (beta, GltD) subunit ().2. Ferredoxin-dependent form in cyanobacteria and plants (Fd-GOGAT from photosynthetic cells, ) displays a single-subunit structure corresponding to the large bacterial subunit (, subfamily )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.The large subunit of GOGAT consists of three domains: N-terminal domain (amidotransferase domain ); central (consisting of and the FMN-binding domain ), and the C-terminal domain (). The N-terminal amidotransferase domain is characterised by a four layer alpha/beta/beta/alpha architecture and is similar to other Ntn-amidotransferases []. It contains the typical catalytic centre of Ntn-amidotransferases, and the N-terminal Cys-1 catalyses the hydrolysis of L-glutamine generating ammonia and the first molecule of L-glutamate []. The second (central) domain consists of and . connects the amidotransferase domain with the FMN-binding domain and has an alpha/beta overall topology []. The FMN-binding domain () has a classic beta/alpha barrel topology. In this domain, the 2-iminoglutarate intermediate, formed upon the addition of ammonia onto 2-oxoglutarate, is reduced by the FMN cofactor producing the second molecule of L-glutamate []. This domain also contains the enzyme 3Fe-4S cluster []. The C-terminal, or GXGXG structural domain, has a right-handed beta-helix topology composing seven beta-helical turns. This domain does not have a direct function in glutamate synthase activity but rather a structural function through extensive interactions with the amidotransferase and FMN-binding domains [, ].The structural data combined with the catalytic properties of GltS indicate that binding of ferredoxin and 2-oxoglutarate to the FMN-binding domain of GltS induce a conformational change in the loop connecting the two catalytic centres. The rearrangement induces a shift in the catalytic elements of the amidotransferase domain, such that it becomes activated [].For additional information please see []. | Short Name: | Glu_synth_euk |
| GO Term | Gene Name |
|---|---|
| GO:0005506 | IPR012220 |
| GO:0010181 | IPR012220 |
| GO:0016040 | IPR012220 |
| GO:0045181 | IPR012220 |
| GO:0050660 | IPR012220 |
| GO:0006537 | IPR012220 |
| GO:0055114 | IPR012220 |
| GO Term | Gene Name |
|---|---|
| GO:0005506 | IPR012220 |
| GO:0010181 | IPR012220 |
| GO:0016040 | IPR012220 |
| GO:0045181 | IPR012220 |
| GO:0050660 | IPR012220 |
| GO:0006537 | IPR012220 |
| GO:0055114 | IPR012220 |
| DB identifier | Type | Name |
|---|---|---|
| IPR006005 | Family | Glutamate synthase, NADH/NADPH, small subunit 1 |
