Activity of thymidine kinase during the cell cycle in Tetrahymena pyriformis.

The presence of thymidine kinase has recently been reported in Tetrahymena pyriformis. The activity pattern for this enzyme was investigated during the cell cycle in both the one heat-shock per cell generation and the starvation-refeed system. Thymidine kinase was found to be a peak enzyme during S-phase in both situations. Nucleoside phosphotransferase was a continuous enzyme in the one heat-shock per cycle system, however, it closely paralleled the thymidine kinase curve during starvation and refeeding.