|Gene:||Gfpt1||Accession Number: G-10016 (MetaCyc)|
Species: Rattus norvegicus
The relative molecular mass of the native enzyme was determined by gel filtration chromatography [Huynh00].
The enzyme is a member of the amidotransferase family, class II. It contains an N-terminal glutamine hydrolase domain and a C-terminal isomerase domain. It has a complex reaction mechanism that involves initial binding of fructose-6-phosphate, followed by glutamine binding. Released ammonia travels through a hydrophobic channel between the hydrolase and isomerase domains. The eukaryotic enzyme is a homotetramer, in contrast to the homodimeric prokaryotic enzyme. The pathway end product UDP-N-acetylglucosamine inhibits the in vitro activity of the eukaryotic, but not the prokaryotic, enzyme. Reviewed in [Milewski06].
The enzyme controls the flux of glucose into the hexosamine pathway. Increased production of the pathway end product UDP-N-acetylglucosamine has been implicated in the development of insulin resistance (in [Broschat02, McKnight92]).
The relative molecular mass of the glutamine:fructose-6-phosphate amidotransferase subunit was determined by SDS-PAGE [Huynh00].
|Map Position: [121,204,274 -> 121,250,160]|
Molecular Weight of Polypeptide: 76.827 kD (from nucleotide sequence), 75 kD (experimental) [Huynh00 ]
Molecular Weight of Multimer: 280 kD (experimental) [Huynh00]
Relationship Links: InterPro:IN-FAMILY:IPR000583 , InterPro:IN-FAMILY:IPR001347 , InterPro:IN-FAMILY:IPR005855 , InterPro:IN-FAMILY:IPR017932 , Pfam:IN-FAMILY:PF00310 , Pfam:IN-FAMILY:PF01380 , Prosite:IN-FAMILY:PS51278 , Prosite:IN-FAMILY:PS51464
Enzymatic reaction of: glutamine:fructose-6-phosphate amidotransferase
Synonyms: glucosamine-6-phosphate synthase, glutamine-fructose-6-phosphate transaminase (isomerizing), GFAT
EC Number: 18.104.22.168
The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.
This reaction is reversible.
In Pathways: UDP-N-acetyl-D-glucosamine biosynthesis II
Glutamine:fructose-6-phosphate amidotransferase catalyzes the first committed step in the cytoplasmic hexosamine biosynthetic pathway in eukaryotes. The reaction is essentially irreversible and consists of two steps: transfer of the glutamine amide group to fructose-6-phosphate, and isomerization of fructose-6-phosphate to N-acetylglucosamine-6-phosphate. The enzyme is highly specific for L-glutamine and fructose-6-phosphate as substrates. Reviewed in [Milewski06].
The rat enzyme has been shown to be competitively inhibited by UDP-N-acetyl glucosamine with respect to fructose-6-phosphate, and noncompetitively with respect to glutamine. It was also found to be competitively inhibited by 6-diazo-5-oxonorleucine with respect to glutamine, and noncompetitively with respect to fructose-6-phosphate (in [Huynh00]). Sulfhydryl reagents inactivated the enzyme, but the inactivation could be reversed by dithiothreitol. 4,4'-Dithiodipyridine was a competitive inhibitor with respect to glutamine [Huynh00].
pH(opt): 7.5 [Huynh00]
Broschat02: Broschat KO, Gorka C, Page JD, Martin-Berger CL, Davies MS, Huang Hc HC, Gulve EA, Salsgiver WJ, Kasten TP (2002). "Kinetic characterization of human glutamine-fructose-6-phosphate amidotransferase I: potent feedback inhibition by glucosamine 6-phosphate." J Biol Chem 277(17);14764-70. PMID: 11842094
McKnight92: McKnight GL, Mudri SL, Mathewes SL, Traxinger RR, Marshall S, Sheppard PO, O'Hara PJ (1992). "Molecular cloning, cDNA sequence, and bacterial expression of human glutamine:fructose-6-phosphate amidotransferase." J Biol Chem 267(35);25208-12. PMID: 1460020
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