4.3.1.B2	L-glutamine + N1-[(5'-phosphoribulosyl)formimino]-5-aminoimidazole-4-carboxamido-1-beta-D-ribofuranosyl 5'-phosphate	the enzyme catalyzes a step in the histidine biosynthetic pathway located at the branch point to de novo purine biosynthesis	Thermus thermophilus	L-glutamate + D-erythro-1-(imidazol-4-yl)glycerol phosphate + 5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxamide	-	?	427463	
4.3.1.B2	L-glutamine + N1-[(5'-phosphoribulosyl)formimino]-5-aminoimidazole-4-carboxamido-1-beta-D-ribofuranosyl 5'-phosphate	the imidazole glycerol phosphate synthase catalyzes formation of the imidazole ring in histidine biosynthesis	Saccharomyces cerevisiae	L-glutamate + D-erythro-1-(imidazol-4-yl)glycerol phosphate + 5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxamide	-	?	427463	
4.3.1.B2	L-glutamine + N1-[(5'-phosphoribulosyl)formimino]-5-aminoimidazole-4-carboxamido-1-beta-D-ribofuranosyl 5'-phosphate	the enzyme is also a glutamine amidotransferase, which produces ammonia in a glutaminase active site and channels it through a 30 A internal tunnel to a cyclase active site	Saccharomyces cerevisiae	L-glutamate + D-erythro-1-(imidazol-4-yl)glycerol phosphate + 5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxamide	-	?	427463	
4.3.1.B2	L-glutamine + N1-[(5'-phosphoribulosyl)formimino]-5-aminoimidazole-4-carboxamido-1-beta-D-ribofuranosyl 5'-phosphate	-	Thermus thermophilus HB8 / ATCC 27634 / DSM 579	L-glutamate + D-erythro-1-(imidazol-4-yl)glycerol phosphate + 5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxamide	-	?	427463	
4.3.1.B2	L-glutamine + N1-[(5'-phosphoribulosyl)formimino]-5-aminoimidazole-4-carboxamido-1-beta-D-ribofuranosyl 5'-phosphate	the enzyme catalyzes a step in the histidine biosynthetic pathway located at the branch point to de novo purine biosynthesis	Thermus thermophilus HB8 / ATCC 27634 / DSM 579	L-glutamate + D-erythro-1-(imidazol-4-yl)glycerol phosphate + 5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxamide	-	?	427463	
4.3.1.B2	L-glutamine + N1-[(5'-phosphoribulosyl)formimino]-5-aminoimidazole-4-carboxamido-1-beta-D-ribofuranosyl 5'-phosphate	-	Saccharomyces cerevisiae	L-glutamate + D-erythro-imidazole-glycerol-phosphate + 5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxamide	-	?	428726	
4.3.1.B2	additional information	the enzyme also shows glutaminase activity. The glutaminase activity of the glutaminase domain is tightly regulated by the acceptor substrate domain. In IGP synthase the glutaminase and N1-[(5'-phosphoribulosyl)formimino]-5-aminoimidazole-4-carboxamido-1-beta-D-ribofuranosyl 5'-phosphate binding sites are separated by 30 A. Using kinetic analyses of site-specific mutants and molecular dynamic simulations, it is determined that an interdomain salt bridge in IGP synthase between D359 and K196 (approximately 16 A from the N1-[(5'-phosphoribulosyl)formimino]-5-aminoimidazole-4-carboxamido-1-beta-D-ribofuranosyl 5'-phosphate binding site) plays a key role in mediating communication between the two active sites. This interdomain contact modulates the glutaminase loop containing the histidine and glutamic acid of the catalytic triad to control glutamine hydrolysis	Saccharomyces cerevisiae	?	-	?	89	
4.3.1.B2	additional information	the enzyme shows a low basal level glutaminase activity that can be enhanced 1000fold in the presence of a nucleotide substrate or analog	Saccharomyces cerevisiae	?	-	?	89	
4.3.1.B2	additional information	the glutaminase activity for the holoenzyme is 0.8% of that in the presence of the nucleotide substrate N1-[(5'-phosphoribulosyl)formimino]-5-aminoimidazole-4-carboxamido-1-beta-D-ribofuranosyl 5'-phosphate	Escherichia coli	?	-	?	89	
4.3.1.B2	additional information	the glutaminase activity of the enzyme is stimulated 4900fold in the presence of the acceptor substrate N1-[(5'-phosphoribulosyl)formimino]-5-aminoimidazole-4-carboxamido-1-beta-D-ribofuranosyl 5'-phosphate	Saccharomyces cerevisiae	?	-	?	89