title: Carbon-13 isotope effects on reactions involving carbamate and carbamoyl phosphate.
abstract: Several 13C isotope effects of relevance to reactions involving carbamate and carbamoyl phosphate have been determined. The fractionation factor of carbamate relative to aqueous CO2 is 1.011; the equilibrium isotope effect on the reaction catalyzed by carbamate kinase is 0.9983. From these data we can calculate that the fractionation factor of carbamoyl phosphate relative to aqueous CO2 is 1.013. The kinetic 13C isotope effect on the decomposition of carbamoyl phosphate to cyanate and phosphate is 1.058. The environment of the carbon atom in carbamate and carbamoyl phosphate and the mechanism of carbamoyl phosphate decomposition are discussed in light of these values.
authors.affiliation: Department of Biochemistry, University of Wisconsin, Madison 53076.
authors.forename: P A
authors.initials: PA
authors.lastname: Tipton
authors.forename: W W
authors.initials: WW
authors.lastname: Cleland
mesh_terms: D002219:Carbamates; D002221:Carbamyl Phosphate; D002247:Carbon Isotopes / Q000494:pharmacology*; D005591:Chemical Fractionation; D005590:Fractional Precipitation; D007700:Kinetics; D010770:Phosphotransferases; D017851:Phosphotransferases (Carboxyl Group Acceptor); D011487:Protein Conformation
chemical_list: D002219:Carbamates; D002247:Carbon Isotopes; D002221:Carbamyl Phosphate; D010770:Phosphotransferases; D017851:Phosphotransferases (Carboxyl Group Acceptor); C019288:carbamate kinase