Comparative analysis of HPLC profile of cytosolic thymidine kinase activity between hepatoma and regenerating liver in rat with reference to phosphorylation.
Thymidine kinase (TK) activity in rat hepatoma JB1 and AH136B was mainly due to cytosolic TK and was much higher than that in rat regenerating liver. Two forms of cytosolic TK, designated as TK-I and TK-II, were revealed in addition to mitochondrial TK in anion-exchange high performance liquid chromatography (HPLC) of the enzyme extract from hepatoma JB1. During incubation of the enzyme extract at 20 degrees C in the presence of phosphatase inhibitor NaF, TK-II activity remained while TK-I activity almost disappeared. Thus, TK-II appeared to be more stable than TK-I. In Western blot analysis, TK-II was much more phosphorylated and exhibiting higher specific activity than TK-I. Meanwhile, regenerating liver derived from the rat 24 h after partial hepatectomy showed only TK-I activity, which completely disappeared after incubation at 20 degrees C even in the presence of NaF. Consequently, the presence of TK-II might account for the higher TK activity in hepatomas than in regenerating liver.
Department of Biochemistry, Chiba University School of Medicine, Chuo-ku, Chiba 260-8670, Japan.
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Lin
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Islam
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Du
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Ohmura
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Hiwasa
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Fujimura
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003600:Cytosol / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008114:Liver Neoplasms, Experimental / Q000201:enzymology*; D008115:Liver Regeneration; D008297:Male; D010766:Phosphorylation; D051381:Rats; D011919:Rats, Inbred Strains; D013937:Thymidine Kinase / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D004791:Enzyme Inhibitors; D013937:Thymidine Kinase