Deoxycytidine triphosphate deaminase of Salmonella typhimurium. Purification and characterization

J Biol Chem. 1975 Jan 25;250(2):609-16.

Abstract

Deoxycytidine triphosphate deaminase (EC 3.5.4., dCTP aminohydrolase) of Salmonella typhimurium LT2 has been pruified 500-fold. The reaction requires the presence of Mg-2plus, Mn-2plus, Ca-2lus, or Co-2plus. Kinetics of the reaction with varying Mg-2plus concentrations, keeping the concentration of dCTP constant, suggests that the true substrate of the reaction is MgdCTP. The dependence of the rate of reaction on dCTP concentration in the presnece of 5-fold excess of Mg-2plus is sigmoid, with a Hill coefficient of 1.7. The enzyme is specifically inhibited by dTTP and dUTP. In the presence of increasing dTTP concentrations the sigmoidicity of the substrate saturation curves increases. With 0.2 and 0.4 mM dTTP the Hill coefficients are 2.6 and 3.0, respectively. Despite several attempts no dissociation of the substrate site and the inhibitor site of the enzyme was achieved.

MeSH terms

  • Binding Sites
  • Cations, Divalent
  • Chromatography
  • Chromatography, Gel
  • Deoxycytidine Monophosphate
  • Deoxyuridine
  • Drug Stability
  • Enzyme Activation / drug effects
  • Hot Temperature
  • Hydrogen-Ion Concentration
  • Kinetics
  • Nucleotide Deaminases / metabolism*
  • Salmonella typhimurium / enzymology*
  • Thymine Nucleotides / pharmacology
  • Uracil Nucleotides / pharmacology

Substances

  • Cations, Divalent
  • Thymine Nucleotides
  • Uracil Nucleotides
  • Deoxycytidine Monophosphate
  • Nucleotide Deaminases
  • Deoxyuridine