[Mitochondrial thymidine kinase isoenzymes from normal and proliferating rat liver tissues].

Isoenzyme composition of thymidine kinase was studied in submitochondrial fractions of liver tissue with various proliferative activity (intact, regenerating livers and Zhaidel ascites hepatoma) using polyacrylamide gel disc electrophoresis. Three zones, corresponding to proteins with Rf 0.1-0.2 (I), Rf 0.5-0.55 (II) and Rf 0.85-0.87 (III) and exhibiting thymidine kinase activity, were found in fractions of cytoplasmic and mitochondrial matrix proteins from resting and proliferating rat liver tissues. In fractions of outer and inner mitochondrial membranes three zones of the enzymatic activity were also observed but two of them did not coincide in the Rf value with the thymidine kinase isoenzymes from cytoplasmic fraction and mitochondrial matrix: I Rf 0.1-0.16, II Rf 0.35-0.4 and III Rf 0.62-0.68. Redistribution of the enzymatic activity between thymidine kinase isozymes occurred in conversion of liver tissue from the resting state to increased proliferation. In these cases slowly migrating enzymatic fraction (Rf 0.1-0.2) was activated in mitochondrial matrix and membranes; formation of TMP, catalyzed by isozymes with fast mobility (Rf 0.5-0.55 in matrix and Rf 0.62-0.68 in membrane fractions of mitochondria), which are typical for intact liver tissue, was decreased, respectively.