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Glutamate Dehydrogenase

Contents 1 General Information 2 Prokaryote 2.1 General Structure 2.2 Specificity 2.3 Allosteric Interactions 3 Eukaryote 3.1 General Structure 3.2 Specificity 3.3 Allosteric Interactions 4 References

General Information

Glutamate Dehydrogenase (GluDH) is a member of the superfamily of amino acid dehydrogenase and functions in the cell to perform they dehydration of α-ketoglutarate to the amino acid glutamate and the reverse reaction.

Reductive amination of α-ketoglutarate is the process by which the ketone is converted to an amine via an imine intermediate. The reverse reaction, oxidative deamination, is the conversion of the amine functional group to a ketone.

Glutamic Acid

Alpha-ketoglutamate.png α-Ketoglutarate

Glutamate dehydrogenase shares sequence homology and structural homology to the superfamily of amino acid dehydrogenases, which suggests divergent evolution.^[1] Because of this property among all proteins in the family, many dehydrogenases can work on multiple substrates.^[2]

However, mammalian GluDH also accomodated allosteric inhibition from GTP and ATP.^[2]

Prokaryote

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General Structure

Prokaryotic glutamate dehydrogenase (GDH) does not have any common quaternary structure among crystallized structures (1EUZ is a hexamer, 1HRD a trimer); however, every prokaryotic structure so far elucidated shows a common overall tertiary structure.^[1]

Each monomer (reguardless of quaternary structure) has two domains: a domain that is a variant of the Rossmann dinucleotide binding fold (), and a domain involved in oligomerization (when it occurs) and contains most of the substrate binding residues (). ^[1]

Specificity

is made up of polar interactions from K89 and S380 and hydrophobic interactions from G90, V377 and A163. The last three residues that make this interaction are highly conserved among amino acid dehydrogenases. ^[1] The polar residues make specific contacts with the glutamine substrate.

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Domain II is in Blue and Domain I is in Purple

Allosteric Interactions

m m m m

...more to come

Eukaryote

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General Structure

Unlike the prokaryotic GluDH, mammalian GluDH has been found to always hexamerize as a dimer of . Also unlike prokaryotic GluDH, the has 48 residue "antenna" that assists in the trimerization process. . These antennae appear to undergo conformational changes as the "mouth" of GluDH opens and closes (see morph below).

Specificity

Allosteric Interactions

References

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1. ↑ ^{1.0 1.1 1.2 1.3} Stillman TJ, Baker PJ, Britton KL, Rice DW. Conformational flexibility in glutamate dehydrogenase. Role of water in substrate recognition and catalysis. J Mol Biol. 1993 Dec 20;234(4):1131-9. PMID:8263917 doi:http://dx.doi.org/10.1006/jmbi.1993.1665
2. ↑ ^{2.0 2.1} Smith TJ, Peterson PE, Schmidt T, Fang J, Stanley CA. Structures of bovine glutamate dehydrogenase complexes elucidate the mechanism of purine regulation. J Mol Biol. 2001 Mar 23;307(2):707-20. PMID:11254391 doi:10.1006/jmbi.2001.4499