6.3.4.2 2'-deoxy-GTP 0 mM guanosine, kact: 1.5/sec, KA: 0.21 mM, Ki: 0.36 mM 674909 6.3.4.2 2'-deoxy-GTP the GTP analogue is capable of activating Gln-dependent CTP formation 674909 6.3.4.2 2-mercaptoethanol required for optimal activity, above 50 mM increase activity to 221% 648987 6.3.4.2 2-mercaptoethanol stimulates 648999 6.3.4.2 6-thio-GTP the GTP analogue is capable of activating Gln-dependent CTP formation 674909 6.3.4.2 6-thioguanosine 5'-triphosphate 0 mM guanosine, kact: 8.5/sec, KA: 0.035 mM, Ki: 0.27 mM 674909 6.3.4.2 dithiothreitol required for optimal activity, above 50 mM increase activity to 223% mM 648987 6.3.4.2 GDP slight activation 648982 6.3.4.2 GMP slight activation 648982 6.3.4.2 GTP - 694484 6.3.4.2 GTP 0 mM guanosine, kact: 10.6/sec, KA: 0.081 mM, Ki: 0.28 mM 674909 6.3.4.2 GTP 0.1 mM guanosine, kact: 10.3/sec, KA: 0.088 mM, Ki: 0.22 mM 674909 6.3.4.2 GTP 0.2 mM guanosine, kact: 8.2/sec, KA: 0.078 mM, Ki: 0.12 mM 674909 6.3.4.2 GTP activates enzyme-catalyzed glutamine hydrolysis 661241 6.3.4.2 GTP activates glutamine reaction, no activation of ammonia reaction 648982 6.3.4.2 GTP activates glutamine-dependent CTP formation at concentrations below 0.2 mM 727139 6.3.4.2 GTP allosteric activator 661713 6.3.4.2 GTP allosteric effector, structural requirements for activation are stringent, but requirements for inhibition are lax. GTP promotes Gln hydrolysis but inhibits Gln-dependent CTP formation at concentrations of over 0.15 mM 674909 6.3.4.2 GTP essential activator when glutamine is the nitrogen source 648985 6.3.4.2 GTP GTP acts a positive allosteric effector for Gln-dependent CTP formation. However, at concentrations exceeding 0.15 mM, GTP inhibits Gln-dependent CTP formation. Moreover, GTP is an inhibitor of NH3-dependent CTP formation at all concentrations 702613 6.3.4.2 GTP not essential, but acts as activator on the glutamine reaction, optimal activation at 1 mM 648987 6.3.4.2 GTP required as allosteric effector to promote reaction with glutamine as substrate, GTP functions by stabilizing the protein conformation that binds the tetrahedral intermediate(s) formed during glutamine hydrolysis 648963 6.3.4.2 GTP required as an allosteric effector to promote glutamine hydrolysis 648962 6.3.4.2 GTP required, activates 690817 6.3.4.2 GTP stimulates reaction with ATP, UTP and Gln 660794 6.3.4.2 GTP the binding of GTP to the allosteric site promotes coordination of the phosphorylation of UTP and hydrolysis of glutamine for optimal efficiency in CTP synthesis rather than just acting to increase the rate of glutamine hydrolysis itself 648964 6.3.4.2 guanosine 5'-tetraphosphate 0 mM guanosine, kact: 4/sec, KA: 0.19 mM, Ki: 0.5 mM 674909 6.3.4.2 guanosine 5'-tetraphosphate the GTP analogue is capable of activating Gln-dependent CTP formation 674909 6.3.4.2 ITP 0 mM guanosine, kact: 5.2/sec, KA: 2.9 mM, Ki: 4.5 mM 674909 6.3.4.2 ITP the GTP analogue is capable of activating Gln-dependent CTP formation 674909 6.3.4.2 additional information activation potency in descending order: GTP = 6-thio-GTP, ITP = guanosine 5'-tetraphosphate, O6-methyl-GTP, 2'-deoxy-GTP, no activation with guanosine, GMP, GDP, 2',3'-dideoxy-GTP, acycloguanosine, and acycloguanosine monophosphate, indicating that the 5'-triphosphate, 2'-OH, and 3'-OH are required for full activation, binding structures and kinetics, overview 674909 6.3.4.2 additional information binding of the substrates ATP and UTP, or the product CTP, promotes oligomerization of CTPS from inactive dimers to active tetramers, Gly142 is critical for nucleotide-dependent oligomerization of CTPS to active tetramers 690817 6.3.4.2 additional information the URA7-encoded enzyme is phosphorylated by protein kinases A and C at Ser424, and these phosphorylations stimulate CTP synthetase activity and increase cellular CTP levels and the utilization of the Kennedy pathway 694934 6.3.4.2 O-methylguanosine 5'-triphosphate 0 mM guanosine, kact: 2.8/sec, KA: 0.13 mM, Ki: 0.29 mM 674909 6.3.4.2 O6-methyl-GTP the GTP analogue is capable of activating Gln-dependent CTP formation 674909