title: Kinetic interaction of 5-AZA-2'-deoxycytidine-5'-monophosphate and its 5'-triphosphate with deoxycytidylate deaminase.
abstract: 5-AZA-2'-deoxycytidine-5'-monophosphate (5-AZA-dCMP) was tested as a substrate, and 5-aza-2'-deoxycytidine-5'-triphosphate (5-AZA-dCTP) was tested as an allosteric effector of purified spleen dCMP deaminase. Graphic analysis of the velocity of deamination of 5-AZA-dCMP versus its concentration gave a hyperbolic curve in which the estimated apparent Km was 0.1 mM. Since this curve was not sigmoidal and 5-AZA-dCMP at low concentrations stimulated the rate of deamination of the natural substrate, dCMP, it was proposed that the binding of 5-AZA-dCMP to the allosteric enzyme dCMP deaminase induced the R form. At substrate saturation, the rate of deamination of dCMP was 100-fold greater than that of 5-AZA-dCMP. dTTP inhibited the deamination of 5-AZA-dCMP with first-order kinetics. This inhibition was reversed by either 5-AZA-dCTP or dCTP. However, dCTP alone produced only a weak activation of the deamination of 5-AZA-dCMP in comparison to the potent activation when dCMP was the substrate. 5-AZA-dCTP was just as effective as dCTP for the allosteric activation of the deamination of dCMP. These results indicate that dCMP deaminase can play an important role in the metabolism 5-aza-2'-deoxycytidine nucleotides and may possibly modulate some of the pharmacological activity of this antimetabolite.
mesh_terms: D000494:Allosteric Regulation; D000818:Animals; D001374:Azacitidine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D003570:Cytidine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D003597:Cytosine Nucleotides; D003844:DCMP Deaminase / Q000378:metabolism*; D003845:Deoxycytosine Nucleotides / Q000494:pharmacology; D007700:Kinetics; D009709:Nucleotide Deaminases / Q000378:metabolism*; D010527:Perissodactyla; D013154:Spleen / Q000201:enzymology
chemical_list: D003597:Cytosine Nucleotides; D003845:Deoxycytosine Nucleotides; C024107:2'-deoxycytidine 5'-triphosphate; D003570:Cytidine Triphosphate; C041519:5-aza-2'-deoxycytidine-5'-monophosphate; C038673:5-aza-2'-deoxycytidine-5'-triphosphate; D009709:Nucleotide Deaminases; D003844:DCMP Deaminase; D001374:Azacitidine