title: Induction of thymidine kinases in phytohaemagglutinin-stimulated human lymphocytes.
abstract: Thymidine kinase (ATP:thymidine 5'-phosphotransferase, EC 2.7.1.21) activity increased approx. 200-fold during transformation of human lymphocytes with phytohaemagglutinin. Two peaks of thymidine kinase (peak IS and peak IIS) were separated from stimulated lymphocytes on DEAE-Sephadex. The activity in peak IS was 20-fold the activity in peak IIS. Only one peak was obtained from normal lymphocytes (peak IIN). The elution volume of this peak was identical to that of peak IIS. The Km values for ATP were 1 mM for peak IS, 0.2 mM for peak IIS and 0.3 mM for peak IIN. 90 micronM dTTP gave 50% inhibition of the activity in peak IS, while the same inhibition of the activities in peak IIS and peak IIN was obtained with only 15 micronM dTTP. Km for thymidine was about 6 micronM for peak IS. The kinetic relation between thymidine and the activity in peak IIS was complex but very similar to that of peak IIN. It is suggested, that a new form of thymidine kinase appears in the lymphocytes due to phytohaemagglutinin stimulation.
mesh_terms: D003201:Computers; D004790:Enzyme Induction / Q000187:drug effects; D006801:Humans; D007700:Kinetics; D037102:Lectins / Q000494:pharmacology; D008213:Lymphocyte Activation; D008214:Lymphocytes / Q000187:drug effects / Q000201:enzymology*; D008433:Mathematics; D013937:Thymidine Kinase / Q000096:biosynthesis*
chemical_list: D037102:Lectins; D013937:Thymidine Kinase