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K Szyfter

Publications and source records attributed to K Szyfter.

42 records · Page 3Linked to original sources
PubMed1985

Pyrimidine salvage enzymes in human tonsil lymphocytes: II. Purification and properties of deoxycytidine kinase.

Human tonsillar lymphocytes incorporate about 7-10 times more [3H]-deoxy-thymidine than [3H]-deoxycytidine at the same extracellular nucleoside concentration, and both incorporations could be inhibited by 10(-5) M arabinosyl-cytosine to 99%. On the other hand, the crude extract of these cells had about 10 times more deoxycytidine kinase than deoxythymidine kinase specific activity, as it was reported previously as well. Therefore, the differences in the labelling of these cells by [3H]-deoxycytidine and [3H]-thymidine cannot be simple due to the different levels of phosphorylating enzymes in the cells. The deoxycytidine kinase of human tonsillar lymphocytes was purified 38.6-fold by DEAE-Sephadex chromatography, and some kinetic and regulatory properties of the purified enzyme were investigated. Deoxycytidine kinase was eluted as a single peak from DEAE-Sephadex column and also from Sephadex G-100 column indicating a molecular weight of about 60 000; no isoenzymes could be detected. During the purification procedure an increase of the enzyme activity was observed suggesting the inhibition of the enzyme in the cells. An apparent Km of 13 microM for deoxycytidine and Ki of 55 microM for arabinosyl-cytosine were found for the tonsillar deoxycytidine kinase. The enzyme was strongly inhibited by dCTP, but not by the other deoxyribonucleoside triphosphates.

Cell-Free System↗
PubMed1984

Analysis of 5'-ends of short DNA fragments excreted by phytohemagglutinin stimulated lymphocytes.

Human peripheral blood lymphocytes were stimulated with phytohemagglutinin and the excreted DNA was isolated from the medium after four days of incubation of cells. The excreted DNA was labeled at the 5'-end with [gamma-32P]ATP and polynucleotide kinase. Analysis of the end-labeled material revealed a size distribution with a chain length of 6 - 60 nucleotides. These short DNA fragments did not contain ribo-nucleotides at their 5'-termini. P1 nuclease digestion did not release specific deoxyribonucleoside monophosphates from the 5'-end of the excreted DNA fragments. These results point to the non-specific degradation of DNA excreted by stimulated lymphocytes.

DNA↗
PubMedDate not supplied

32P-postlabelling analysis of DNA adducts in humans: adduct distribution and method improvement.

32P-Postlabelling was applied to study the distribution of adducts in white blood cells of foundry workers exposed to polycylic aromatic hydrocarbons. The distribution of the adducts among 63 workers followed an apparently trimodal pattern, which could relate to polymorphism in PAH metabolism. A modified postlabelling method is described and some parameters were tested for optimal labelling. The total volume of the polynucleotide kinase reaction is 2 microliters, which decreases exposure to radioactivity and costs of isotopes.

Animals↗