Reversible dissociation of a carbomoyl phosphate synthase-aspartate transcarbamoylase-dihydroorotase complex from ovarian eggs of Rana catesbeiana: effect of uridine triphosphate and other modifiers
Glutamine-dependent carbamoyl phosphate synthase (ATP:carbamate phosphotransferase (dephosphorylating), EC 2.7.2.9), aspartate transcarbamoylase (carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2) and dihydroorotase (L-5,6-dihydroorotate amidohydrolase, EC 3.5.2.3), are copurified as a high-molecular-weight complex from extracts of unfertilized eggs of Rana catesbeiana. UTP is required to maintain the integrity of the complex during the last two purification steps. Removal of the nucleotide results in dissociation of the complex. Based on sedimentation behavior in glycerol gradients, the dissociated carbamoyl phosphate synthase has an apparent molecular weight of 260,000 +- 20,000 and that of dihydroorotase is estimated at 280,000 +- 20,000. Aspartate transcarbamoylase is broadly distributed over the gradient. The addition of ATP, 5-phosphoribosyl-1-pyrophosphate, Mg/sup + +/, or inorganic phosphate to the dissociated complex results in the appearance of a peak of aspartate transcarbamoylase activity with an apparent molecular weight of 110,000 +- 10,000. Incubation of a mixture of the dissociated enzymes with UTP and Mg/sup + +/ leads to their reassociation into the high-molecular-weight complex.
- Research Organization:
- Univ. of Wisconsin, Madison
- OSTI ID:
- 7232000
- Journal Information:
- Proc. Natl. Acad. Sci. U.S.A.; (United States), Journal Name: Proc. Natl. Acad. Sci. U.S.A.; (United States) Vol. 72:5; ISSN PNASA
- Country of Publication:
- United States
- Language:
- English
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