Aspartate carbamyltransferase

Thiosulfate cyanide sulfurtransferase symmetry in 78 TTiiouridine 234 Three-dimensional structures of aconitase 689 adenylate kinase 655 aldehyde oxido-reductase 891 D-amino acid oxidase 791 a-amylase, pancreatic 607 aspartate aminotransferase 57,135 catalytic intermediates 752 aspartate carbamyltransferase 348 aspartate chemoreceptor 562 bacteriophage P22 66 cadherin 408 calmodulin 317 carbonic acid anhydrase I 679 carboxypeptidase A 64 catalase 853 cholera toxin 333, 546 chymotrypsin 611 citrate synthase 702, 703 cutinase 134 cyclosporin 488 cytochrome c 847 cytochrome c peroxidase 849 dihydrofolate reductase 807 DNA 214, 223,228,229, 241 DNA complex... 

Reichard found that carbamyl aspartate synthesis would take place in crude liver preparations if carbamyl phosphate and aspartate were provided and showed that the enzyme responsible, aspartate carbamyltransferase, was not the same as that which formed citrulline, but apparently shared carbamyl phosphate with it. 

Aspartate carbamyltransferase activity is widely distributed, having been found in rat tissues, pigeon liver, yeast, and in E. colt. Rapidly growing tissues such as tumor and regenerating liver have high concentrations of the enzyme (28). 

When the catalytic and regulatory subunits are dissociated, the catal3rtic activity, measured with saturating concentrations of carbamyl phosphate, displays conventional hyperbolic kinetics with respect to aspartate concentration. However, sigmoidal kinetics are shown by the native aspartate carbamyltransferase, in which form the subunits are associated. In the presence of CTP, the sigmoidicity of the rate-aspartate curve is further increased, with the effect that the apparent Michaelis constant for aspartate is increased. ATP competes with CTP for the regulatory site, with the result that the CTP inhibitory effect is antagonized. 

The synthesis of the E. coli aspartate carbamyltransferase is under repressor control (28) , this is one of the classical examples of metabolite control by repression of enzyme S3mthesis. 

Carbamoylphosphate L-aspartate carbamoyl-transferase Aspartate carbamyltransferase... 

Aspartate carbamyltransferase 2 dihydroorotase 3 orotate reductase 4 orotate phosphoribosyl-transferase 5 orotidine-5 -phosphate decarboxylase 6 cytidylate kinase, nucleotide diphosphate kinase 7 cytidine triphosphate synthetase 8 nucleoside monophosphate kinase, ribonucleoside diphosphate reductase, phosphatase 9 thymidylate synthase... 

Bourget, P. A., and Tremblay, G. C., 1972, Control of pyrimidine biosynthesis in rat liver by feedback inhibition of aspartate carbamyltransferase, Biochem. Biophys. Res. Com-mun. 46 752. 

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