UniProt functional annotation for Q5SIA8



	UniProt functional annotation for Q5SIA8

UniProt code: Q5SIA8.

Organism: Thermus thermophilus (strain ATCC 27634 / DSM 579 / HB8).

Taxonomy: Bacteria; Deinococcus-Thermus; Deinococci; Thermales; Thermaceae; Thermus.

Function: Catalyzes the ATP-dependent amination of UTP to CTP with either L-glutamine or ammonia as the source of nitrogen (PubMed:15296735). Regulates intracellular CTP levels through interactions with the four ribonucleotide triphosphates (By similarity). {ECO:0000255|HAMAP-Rule:MF_01227, ECO:0000269|PubMed:15296735}.

Catalytic activity: Reaction=ATP + H2O + L-glutamine + UTP = ADP + CTP + 2 H(+) + L- glutamate + phosphate; Xref=Rhea:RHEA:26426, ChEBI:CHEBI:15377, ChEBI:CHEBI:15378, ChEBI:CHEBI:29985, ChEBI:CHEBI:30616, ChEBI:CHEBI:37563, ChEBI:CHEBI:43474, ChEBI:CHEBI:46398, ChEBI:CHEBI:58359, ChEBI:CHEBI:456216; EC=6.3.4.2; Evidence={ECO:0000255|HAMAP-Rule:MF_01227, ECO:0000269|PubMed:15296735};

Activity regulation: Allosterically activated by GTP, when glutamine is the substrate (PubMed:15296735). GTP has no effect on the reaction when ammonia is the substrate. The allosteric effector GTP functions by stabilizing the protein conformation that binds the tetrahedral intermediate(s) formed during glutamine hydrolysis. Inhibited by the product CTP, via allosteric rather than competitive inhibition (By similarity). {ECO:0000255|HAMAP-Rule:MF_01227, ECO:0000269|PubMed:15296735}.

Biophysicochemical properties: Kinetic parameters: KM=0.24 mM for L-glutamine (at unsaturating levels of ATP and UTP (0.5 mM)) {ECO:0000269|PubMed:15296735}; KM=0.22 mM for L-glutamine (in the presence of GTP) {ECO:0000269|PubMed:15296735}; KM=0.37 mM for UTP {ECO:0000269|PubMed:15296735}; Note=kcat is 7.4 sec(-1) toward L-glutamine at unsaturating levels of ATP and UTP (0.5 mM) and 40 sec(-1) in the presence of GTP. kcat is 260 sec(-1) toward UTP. {ECO:0000269|PubMed:15296735};

Pathway: Pyrimidine metabolism; CTP biosynthesis via de novo pathway; CTP from UDP: step 2/2. {ECO:0000255|HAMAP-Rule:MF_01227}.

Subunit: Homotetramer in the presence of UTP and ATP. Is in a protein concentration-dependent equilibrium between monomer, dimer, and tetramer in the absence of UTP and ATP. {ECO:0000269|PubMed:15296735}.

Miscellaneous: CTPSs have evolved a hybrid strategy for distinguishing between UTP and CTP. The overlapping regions of the product feedback inhibitory and substrate sites recognize a common feature in both compounds, the triphosphate moiety. To differentiate isosteric substrate and product pyrimidine rings, an additional pocket far from the expected kinase/ligase catalytic site, specifically recognizes the cytosine and ribose portions of the product inhibitor. {ECO:0000255|HAMAP-Rule:MF_01227}.

Similarity: Belongs to the CTP synthase family. {ECO:0000255|HAMAP- Rule:MF_01227}.

Annotations taken from UniProtKB at the EBI.


Organism:		Thermus thermophilus (strain ATCC 27634 / DSM 579 / HB8).
Taxonomy:		Bacteria; Deinococcus-Thermus; Deinococci; Thermales; Thermaceae; Thermus.



Function:		Catalyzes the ATP-dependent amination of UTP to CTP with either L-glutamine or ammonia as the source of nitrogen (PubMed:15296735). Regulates intracellular CTP levels through interactions with the four ribonucleotide triphosphates (By similarity). {ECO:0000255\|HAMAP-Rule:MF_01227, ECO:0000269\|PubMed:15296735}.


Catalytic activity:		Reaction=ATP + H2O + L-glutamine + UTP = ADP + CTP + 2 H(+) + L- glutamate + phosphate; Xref=Rhea:RHEA:26426, ChEBI:CHEBI:15377, ChEBI:CHEBI:15378, ChEBI:CHEBI:29985, ChEBI:CHEBI:30616, ChEBI:CHEBI:37563, ChEBI:CHEBI:43474, ChEBI:CHEBI:46398, ChEBI:CHEBI:58359, ChEBI:CHEBI:456216; EC=6.3.4.2; Evidence={ECO:0000255\|HAMAP-Rule:MF_01227, ECO:0000269\|PubMed:15296735};
Activity regulation:		Allosterically activated by GTP, when glutamine is the substrate (PubMed:15296735). GTP has no effect on the reaction when ammonia is the substrate. The allosteric effector GTP functions by stabilizing the protein conformation that binds the tetrahedral intermediate(s) formed during glutamine hydrolysis. Inhibited by the product CTP, via allosteric rather than competitive inhibition (By similarity). {ECO:0000255\|HAMAP-Rule:MF_01227, ECO:0000269\|PubMed:15296735}.
Biophysicochemical properties:		Kinetic parameters: KM=0.24 mM for L-glutamine (at unsaturating levels of ATP and UTP (0.5 mM)) {ECO:0000269\|PubMed:15296735}; KM=0.22 mM for L-glutamine (in the presence of GTP) {ECO:0000269\|PubMed:15296735}; KM=0.37 mM for UTP {ECO:0000269\|PubMed:15296735}; Note=kcat is 7.4 sec(-1) toward L-glutamine at unsaturating levels of ATP and UTP (0.5 mM) and 40 sec(-1) in the presence of GTP. kcat is 260 sec(-1) toward UTP. {ECO:0000269\|PubMed:15296735};
Pathway:		Pyrimidine metabolism; CTP biosynthesis via de novo pathway; CTP from UDP: step 2/2. {ECO:0000255\|HAMAP-Rule:MF_01227}.
Subunit:		Homotetramer in the presence of UTP and ATP. Is in a protein concentration-dependent equilibrium between monomer, dimer, and tetramer in the absence of UTP and ATP. {ECO:0000269\|PubMed:15296735}.
Miscellaneous:		CTPSs have evolved a hybrid strategy for distinguishing between UTP and CTP. The overlapping regions of the product feedback inhibitory and substrate sites recognize a common feature in both compounds, the triphosphate moiety. To differentiate isosteric substrate and product pyrimidine rings, an additional pocket far from the expected kinase/ligase catalytic site, specifically recognizes the cytosine and ribose portions of the product inhibitor. {ECO:0000255\|HAMAP-Rule:MF_01227}.
Similarity:		Belongs to the CTP synthase family. {ECO:0000255\|HAMAP- Rule:MF_01227}.