Thymidine kinase. A novel affinity chromatography of the enzyme and its regulation by phosphorylation in Physarum polycephalum.

dThd bound to epoxy-activated Sepharose results in a high specific affinity adsorbent, which was used to purify Physarum dThd kinase 8000-fold. With this purified enzyme, it was proved that dThd kinase exists in five enzyme variants in Physarum polycephalum, the acidic forms being phosphorylated. This protein modification is discussed under the aspect of the regulation of this enzyme.