title: Characterization of DNA kinase from calf thymus.
abstract: DNA kinase has been purified to homogeneity from calf thymus. The purified enzyme, with a specific activity of 16.7 units/mg protein at 25 degrees C, exhibited a sharp pH/activity curve with a pH optimum at 5.5 and low activity at alkaline pH. The molecular weight of the enzyme was estimated by dodecylsulfate/polyacrylamide gel electrophoresis to be 5.4 X 10(4). The enzyme has a sedimentation coefficient of 4.0 S. An apparent molecular weight of 5.6 X 10(4) and a Stokes' radius of 3.3 nm were estimated by gel-filtration on Sephadex G-100. The enzyme phosphorylates neither yeast RNA nor poly(A) instead of DNA. Compared with rat liver DNA kinase, calf thymus DNA kinase is relatively resistant to the inhibition by sulfate (Ki = 7 mM) and pyrophosphate (Ki = 5 mM). The enzyme activity is markedly stimulated by polyamines at the sub-optimal concentration of Mg2+ but not by monovalent cations.
mesh_terms: D000818:Animals; D002417:Cattle; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D015636:Magnesium Chloride; D010770:Phosphotransferases / Q000378:metabolism*; D011116:Polynucleotide 5'-Hydroxyl-Kinase / Q000378:metabolism*; D011700:Putrescine / Q000494:pharmacology; D013095:Spermidine / Q000494:pharmacology; D013096:Spermine / Q000494:pharmacology; D013379:Substrate Specificity; D013950:Thymus Gland / Q000201:enzymology*
chemical_list: D015636:Magnesium Chloride; D013096:Spermine; D010770:Phosphotransferases; D011116:Polynucleotide 5'-Hydroxyl-Kinase; D008274:Magnesium; D013095:Spermidine; D011700:Putrescine