[An uncommon form of thymidine kinase in breast cancers].

An unusual form of thymidine kinase has been found in cytosols from breast cancers. It differs from the adult and fetal isoenzymes of thymidine kinase in so far as its activity could not be isolated from that of thymidylate kinase. Following sucrose density gradients, electrofocusing, ion exchange chromatography or molecular sieving, both activities appeared as a single peak. These facts suggest that they could be attributed to a single multifunctional protein.