title: Carbamyl phosphate synthetase of Escherichia coli uses the same diastereomer of adenosine-5'-[2-thiotriphosphate] at both ATP sites.
abstract: Carbamyl phosphate synthetase from Escherichia coli has been shown to use only the A isomer of adenosine-5'-[2-thiotriphosphate] in both the ATPase reaction (MgATP HCO3- leads to MgADP + Pi) and the carbamyl phosphate synthesis reaction (2MgATP + HCO3- + L-glutamine leads to 2MgADP + Pi + carbamyl-P + L-glutamate). The B isomer was less than 5% as reactive. In the reverse reaction, only the A isomer of adenosine-5'-[2-thiotriphosphate] is synthesized from adenosine-5'-[2-thiodiphosphate] and carbamyl-P as determined by 31P NMR and a coupled enzymatic assay with Cd2+- hexokinase. It is therefore proposed that carbamyl phosphate synthetase uses the same diastereomer of MgATP at both ATP sites.
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives*; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing) / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D009682:Magnetic Resonance Spectroscopy; D010770:Phosphotransferases / Q000378:metabolism*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013873:Thionucleotides
chemical_list: D013873:Thionucleotides; D000255:Adenosine Triphosphate; D010770:Phosphotransferases; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing)