title: Allosteric effects of cortisol, estradiol, progesterone and of the DNA-sequences poly d(A-T) and poly d(C-G) on the adenosine and thymidine phosphorylating activity of the nuclear nucleoside-nucleotide phosphotransferase C.
abstract: The ATP-synthesis of the nuclear nucleoside-nucleotide phosphotransferase C was stimulated by progesterone alone and in combination with poly d(A-T) at 10(-10)-10(-9) M, by estradiol/poly d(A-T) at 5-10(-9) M, by cortisol alone and in combination with poly d(A-T) at 10(-9)-10(-8) M and by poly d(A-T) alone. No effect was observed using poly d(C-G). Using increasing adenosine/dTTP as substrates, cortisol, progesterone, estradiol/poly d(A-T) and poly d(A-T) alone caused positive cooperativity of the substrate saturation curves of the allosteric enzyme C by lowering the apparent Ks 0.5-values and by altering Vmax. The dTTP-synthesis of enzyme C was stimulated by both poly d(A-T) and poly d(C-G) alone and in combination with low estradiol (up to 10(-10) M)-and with higher progesterone concentrations (10(-8)-10(-7) M), whereas cortisol inhibited at higher concentrations completely. Using increasing thymidine/ATP as substrates progesterone and estradiol, also in combination with poly d(A-T) were positive effectors of the substrate saturation curves of enzyme C. By this, the apparent Ks 0.5-values or Vmax were changed. Cortisol could be shown to be a negative effector.
mesh_terms: D000241:Adenosine / Q000378:metabolism; D000494:Allosteric Regulation / Q000187:drug effects; D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000008:administration & dosage*; D006854:Hydrocortisone / Q000008:administration & dosage*; D007700:Kinetics; D008114:Liver Neoplasms, Experimental / Q000201:enzymology*; D008297:Male; D010770:Phosphotransferases / Q000378:metabolism*; D011067:Poly dA-dT / Q000008:administration & dosage*; D011089:Polydeoxyribonucleotides / Q000008:administration & dosage*; D011374:Progesterone / Q000008:administration & dosage*; D051381:Rats; D013936:Thymidine / Q000378:metabolism
chemical_list: D011089:Polydeoxyribonucleotides; D011067:Poly dA-dT; C019530:poly(dC-dG); D011374:Progesterone; D004958:Estradiol; D010770:Phosphotransferases; C021898:nucleotide phosphotransferase; D000241:Adenosine; D013936:Thymidine; D006854:Hydrocortisone