The phosphorylation of 5 substituted deoxycytidine analogues by deoxycytidine kinase was studied in extracts of mouse and human lymphoid cells. The apparent Km for the phosphorylation of 5 bromodeoxycytidine in extracts of mouse lymphoma cells was 2.0 mM, in contrast to a Km of 10 μM for deoxycytidine phosphorylation. The apparent Km for the phosphorylation of 5 methyldeoxycytidine by the mouse enzyme was 80 μM. The affinity of mouse deoxycytidine kinase for 5 iododeoxycytidine was lower than for 5 bromodeoxycytidine, whereas its affinity for 5 fluorodeoxycytidine was similar to that for deoxycytidine. With human deoxycytidine kinase the apparent Km was 0.4 mM for 5 bromodeoxycytidine, as compared to 2.0 μM for deoxycytidine. These results suggest that the activity of deoxycytidine kinase is affected by the size of substitutions in position 5 of its substrate. This restricted substrate specificity of deoxycytidine kinase could limit the utilization of 5 bromodeoxycytidine for DNA synthesis.
|Original language||English (US)|
|Number of pages||7|
|State||Published - Dec 1 1973|
ASJC Scopus subject areas
- Molecular Medicine