title: Regulatory properties of carbamoyl-phosphate synthetase II from the parasitic protozoan Crithidia fasciculata.
abstract: 1. At the lowered concentrations of 0.5 mM ATP and 1.5 mM MgCl2, 2.0 mM UTP, UDP and UMP inhibited the activity of Crithidia fasciculata carbamoyl-phosphate synthetase II by about 65, 80 and 40% respectively. 2. The result suggests that feedback inhibition of the activity by uridine nucleotides is a mechanism of regulation of the de novo pyrimidine biosynthetic pathway in C. fasciculata. 3. ADP, AMP and CDP inhibited the activity (about 70, 40 and 40%). 4. Excess Mg2+ at around 1 mM, relative to the ATP concentration, was required for the maximum activity. 5. 5-Phosphoribosyl 1-pyrophosphate had no significant effect on the activity under various conditions examined.
mesh_terms: D000818:Animals; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing) / Q000378:metabolism*; D003421:Crithidia / Q000201:enzymology*; D005246:Feedback; D007700:Kinetics; D008025:Ligases / Q000378:metabolism*; D010754:Phosphoribosyl Pyrophosphate / Q000494:pharmacology; D012265:Ribonucleotides / Q000494:pharmacology
chemical_list: D012265:Ribonucleotides; D010754:Phosphoribosyl Pyrophosphate; D008025:Ligases; D002223:Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing)