{PDOC00406} {PS51278; GATASE_TYPE_2} {BEGIN} **************************************************** * Glutamine amidotransferase type 2 domain profile * **************************************************** A large group of biosynthetic enzymes are able to catalyze the removal of the ammonia group from glutamine and then to transfer this group to a substrate to form a new carbon-nitrogen group. This catalytic activity is known as glutamine amidotransferase (GATase) (EC 2.4.2.-) [1]. The GATase domain exists either as a separate polypeptidic subunit or as part of a larger polypeptide fused in different ways to a synthase domain. On the basis of sequence similarities two classes of GATase domains have been identified [2,3]: class-I (also known as trpG-type or triad) (see ) and class-II (also known as purF-type or Ntn). Class-II (or type 2) GATase domains have been found in the following enzymes: - Amido phosphoribosyltransferase (glutamine phosphoribosylpyrophosphate amidotransferase) (EC 2.4.2.14). An enzyme which catalyzes the first step in purine biosynthesis, the transfer of the ammonia group of glutamine to PRPP to form 5-phosphoribosylamine (gene purF in bacteria, ADE4 in yeast). - Glucosamine--fructose-6-phosphate aminotransferase (EC 2.6.1.16). This enzyme catalyzes a key reaction in amino sugar synthesis, the formation of glucosamine 6-phosphate from fructose 6-phosphate and glutamine (gene glmS in Escherichia coli, nodM in Rhizobium, GFA1 in yeast). - Asparagine synthetase (glutamine-hydrolyzing) (EC 6.3.5.4). This enzyme is responsible for the synthesis of asparagine from aspartate and glutamine. - Glutamate synthase (gltS), an enzyme which participates in the ammonia assimilation process by catalyzing the formation of glutamate from glutamine and 2-oxoglutarate. Glutamate synthase is a multicomponent iron-sulfur flavoprotein and three types occur which use a different electron donor: NADPH-dependent gltS (large chain) (EC 1.4.1.13), ferredoxin-dependent gltS (EC 1.4.7.1) and NADH-dependent gltS (EC 1.4.1.14) [4]. The active site is formed by a cysteine present at the N-terminal extremity of the mature form of all these enzymes [5-8]. Two other conserved residues, Asn and Gly, form an oxyanion hole for stabilization of the formed tetrahedral intermediate. An insert of ~120 residues can occur between the conserved regions [4]. In some class-II GATases (for example in Bacillus subtilis or chicken amido phosphoribosyltransferase) the enzyme is synthesized with a short propeptide which is cleaved off post-translationally by a proposed autocatalytic mechanism. Nuclear-encoded Fd-dependent gltS have a longer propeptide which may contain a chloroplast-targeting peptide in additon to the propeptide that is excised on enzyme activation [4]. The 3-D structure of the GATase type 2 domain forms a four layer alpha/beta/beta/alpha architecture (see ) which consists of a fold similar to the N-terminal nucleophile (Ntn) hydrolases. These have the capacity for nucleophilic attack and the possibility of autocatalytic processing. The N-terminal position and the folding of the catalytic Cys differ strongly from the Cys-His-Glu triad which forms the active site of GATases of type 1 (see ). The profile we developed covers the entire GATase type 2 domain. -Sequences known to belong to this class detected by the profile: ALL. -Other sequence(s) detected in Swiss-Prot: NONE. -Last update: November 2006 / Pattern removed, profile added and text revised. [ 1] Buchanan J.M. "The amidotransferases." Adv. Enzymol. Relat. Areas Mol. Biol. 39:91-183(1973). PubMed=4355768 [ 2] Weng M.L., Zalkin H. "Structural role for a conserved region in the CTP synthetase glutamine amide transfer domain." J. Bacteriol. 169:3023-3028(1987). PubMed=3298209 [ 3] Nyunoya H., Lusty C.J. "Sequence of the small subunit of yeast carbamyl phosphate synthetase and identification of its catalytic domain." J. Biol. Chem. 259:9790-9798(1984). PubMed=6086650 [ 4] Vanoni M.A., Curti B. "Glutamate synthase: a complex iron-sulfur flavoprotein." Cell. Mol. Life Sci. 55:617-638(1999). PubMed=10357231 [ 5] Vollmer S.J., Switzer R.L., Hermodson M.A., Bower S.G., Zalkin H. "The glutamine-utilizing site of Bacillus subtilis glutamine phosphoribosylpyrophosphate amidotransferase." J. Biol. Chem. 258:10582-10585(1983). PubMed=6411716 [ 6] Van Heeke G., Schuster S.M. "The N-terminal cysteine of human asparagine synthetase is essential for glutamine-dependent activity." J. Biol. Chem. 264:19475-19477(1989). PubMed=2573597 [ 7] Massiere F., Badet-Denisot M.A. "The mechanism of glutamine-dependent amidotransferases." Cell. Mol. Life Sci. 54:205-222(1998). PubMed=9575335 [ 8] van den Heuvel R.H.H., Curti B., Vanoni M.A., Mattevi A. "Glutamate synthase: a fascinating pathway from L-glutamine to L-glutamate." Cell. Mol. Life Sci. 61:669-681(2004). PubMed=15052410; DOI=10.1007/s00018-003-3316-0 -------------------------------------------------------------------------------- PROSITE is copyrighted by the SIB Swiss Institute of Bioinformatics and distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives (CC BY-NC-ND 4.0) License, see https://prosite.expasy.org/prosite_license.html -------------------------------------------------------------------------------- {END}