Cofactors

FAD; FMN; Iron-sulfur.

Reaction Mechanism

glutamate synthase (ferredoxin) By Reference

Binds a [3Fe-4S] cluster as well as FAD and FMN. The protein is composed of two domains, one hydrolysing L-glutamine to ammonia and L-glutamate (cf. EC 3.5.1.2, glutaminase), the other combines the produced ammonia with 2-oxoglutarate to produce a second molecule of L-glutamate. The ammonia is channelled through a tunnel in the active protein. This tunnel provides a micro-environment that prevents the protonation of the ammonia, crucial as the enzyme will not function with ammonium as the nitrogen source. The hydrolysis reaction only occurs when ferredoxin and 2-oxoglutarate are bound to the protein.




• Summary
• Step 1
• Step 2
• Step 3
• Step 4
• Step 5
• Step 6
• Step 7
• Step 8
• Step 9
• Step 10
• Products

The overall transformation occurs in two halves:

1. The hydrolysis of glutamine to glutamate and ammonia. This reaction occurs in the N-terminal amidotransferase domain (CATH code 3.60.20.10, residues 1-422) and proceeds via the classical cysteine covalent intermediate.
2. The second half reaction occur in the FMN-binding domain (CATH code 3.20.20.70, residues 787-1223). In this reaction the ammonia initiates a nucleophilic attack on the C2 carbonyl carbon of the 2-oxoglutarate substrate. The FMN cofactor then donates a hydride ion to the intermediate and Ferredoxin regenerates the FMN cofactor.

Catalytic Residues

AA	Uniprot	Uniprot Resid	PDB	PDB Resid
Asn	P55038	263	1ofd	227
Arg	P55038	67	1ofd	31
Cys	P55038	37	1ofd	1
Gly	P55038	264	1ofd	228
Glu	P55038	939	1ofd	903
Gln	P55038	1005	1ofd	969
Lys	P55038	1008	1ofd	972
Gln	P55038	1014	1ofd	978
Phe	P55038	243	1ofd	207
Cys	P55038	37	1ofd	1

Step Components

overall product formed, proton transfer, enzyme-substrate complex formation, native state of cofactor regenerated, intermediate formation, dehydration, schiff base formed, cofactor used, electron relay, enzyme-substrate complex cleavage, radical termination, redox reaction, intermediate terminated, native state of enzyme regenerated, aromatic unimolecular elimination by the conjugate base, electron transfer, intermediate collapse, hydride transfer, radical formation, overall reactant used, inferred reaction step, proton relay, unimolecular elimination by the conjugate base, bimolecular nucleophilic addition, deamination



Step 1.

The N-terminus of Cys1 deprotonates deprotonates water, which deprotonates the thiol group of Cys1, initiating a nucleophilic attack on the amide carbon in an addition reaction.



Step 2.

The oxyanion initiates an elimination that cleaves ammonia from the bound L-glutamine substrate. Ammonia deprotonates water, which deprotonates the N-terminus of Cys1.



Step 3.

The N-terminus of Cys1 deprotonates water, which deprotonates another water that initiates a nucleophilic attack on the carbonyl carbon of the covalently bound intermediate in an addition reaction.



Step 4.

The oxyanion initiates an elimination that cleaves the C-S bond, the thiolate of Cys1 deprotonates water, which deprotonates the N-terminus of Cys1



Step 5.

Ammonia initiates a nucleophilic attack on the C2 carbonyl carbon of the 2-oxoglutarate substrate in an addition reaction. The oxyanion formed deprotonates the bound ammonium.



Step 6.

The amine initiates an elimination of the bound hydroxide as water, which deprotonates Lys972.



Step 7.

FMN eliminates a hydride ion, which adds to the C2 imine carbon in an addition reaction.



Step 8.

Lys972 deprotonates water in an inferred step.



Step 9.

Ferredoxin donates a single electron, which is transferred to FMN through an iron-sulfur cluster. FMN deprotonates water.



Step 10.

A second ferredoxin donates a single electron, which is transferred to FMN through an iron-sulfur cluster, which regenerates the reduced form of FMN.



Products.

The products of the reaction.

View Reaction Mechanisms in M-CSA

Reaction Parameters

There are no kinetic parameters information for this Enzyme

Associated Proteins

Citations

• CBSX2 is required for the efficient oxidation of chloroplast redox-regulated enzymes in darkness.
• Transcriptome Analysis of Macrophytes' Myriophyllum spicatum Response to Ammonium Nitrogen Stress Using the Whole Plant Individual.
• Nitrogen Journey in Plants: From Uptake to Metabolism, Stress Response, and Microbe Interaction.
• Nitrogen assimilation plays a role in balancing the chloroplastic glutathione redox state under high-light conditions
• Transcriptome Profiling Provides Insights into the Early Development of Tiller Buds in High- and Low-Tillering Orchardgrass Genotypes
• CO₂ recycling by phosphoenolpyruvate carboxylase enables cassava leaf metabolism to tolerate low water availability.
• Photorespiration: regulation and new insights on the potential role of persulfidation.
• Glycine-Induced Phosphorylation Plays a Pivotal Role in Energy Metabolism in Roots and Amino Acid Metabolism in Leaves of Tea Plant.
• Insights into the Lysine Acetylome of the Haloarchaeon Haloferax volcanii during Oxidative Stress by Quantitative SILAC-Based Proteomics.
• Physiochemical and molecular responses of the diatom Phaeodactylum tricornutum to illumination transitions.
• Salt Stress-Related Mechanisms in Leaves of the Wild Barley Hordeum spontaneum Generated from RNA-Seq Datasets.