Intracellular Distribution of Various Enzymes Concerned with DNA Synthesis from Normal and Regenerating Rat Liver, and Yoshida Sarcoma

Abstract

During the fractionation of various enzymes concerned with DNA synthesis from the postmicrosomal supernatant fraction of various tissues, DNA polymerase [EC 2.7.7.7], thymidine kinase [EC 2.7.1.75], dTMP kinase [EC 2.7.4.9], deoxycytidine kinase [EC 2.7.1.74], and deoxycytidine monophosphokinase (dCMP kinase) [EC 2. 7. 4. 14] were found in the pellet fraction of postmicrosomal supernatant. Further, the uridine kinase [EC 2. 7. 1.48] and aspartate transcarbamylase [EC 2.1.3.2] activi-ties of postmicrosomal supernatant from various tissues were also present in this pellet fraction. The activities of DNA polymerase, thymidine kinase, uridine kinase, and aspartate transcarbamylase from normal and regenerating rat liver, and Yoshida sarcoma were higher in the pellet fraction than in the supernatant. On the other hand, the activities of dTMP kinase, dCMP kinase, and orotidine-5'-phosphate de-carboxylase [EC 4. 1. 1. 23] were lower in the pellet fraction than in the supernatant.
The pellet fractions of regenerating rat liver and Yoshida sarcoma showed a remarkable incorporation of various precursors (thymidine, dTMP, deoxycytidine, and dCMP) into DNA in the presence of a suitable DNA template, ATP and all four deoxynucleoside 5'-triphosphates for DNA synthesis. Normal adult rat liver catalyzed a much smaller incorporation of all these precursors, except for dCMP.