Showing papers by "Yung-Chi Cheng published in 1976"
TL;DR: Two forms of deoxythymidine kinase from blast cells of acute myelocytic leukemia were identified by electrophoresis and separated and purified by differential affinity column chromatography which resulted in 2416- and 1634-fold purification of the cytoplasmic and mitochondrial enzymes, respectively.
160 citations
TL;DR: The purified herpes simplex virus type I and II deoxythymidine kinase had different activation energies when Mg2+ATP and deoxymidine were used as substrates, but showed the same sensitivity toward ammonium sulfate inhibition.
137 citations
TL;DR: Initial velocity as well as product inhibition studies suggest that the cytoplasmic isozyme catalyzes the reaction via a "sequential" mechanism, in contrast, mitochondrial deoxythymidine kinase catalyze the reaction through a "ping-pong" mechanism.
Abstract: Cytoplasmic and mitochondrial deoxythymidine kinase isozymes derived from the blast cells of acute myelocytic leukemia differ in their substrate specificity and kinetic behavior. These enzymes require divalent cations for their activity. The data suggest that the major role of idvalent cations is to chelate with ATP; the complex thus formed serves as the phosphate donor for the reaction. The activity of various triphosphate nucleosides as a phosphate donor for cytoplasmic deoxythymidine kinase is as follows: ATP = dATP greater than ara-ATP greater than GTP greater than CTP greater than dGTP = dCTP greater than dUTP, whereas for mitochondrial deoxythymidine kinase, the order of activity is ATP greater than CTP greater than UTP = dATP greater than ara-ATP greater than dGTP = dCTP greater than dUTP. Neither IdUTP nor dTTP could serve as a phosphate donor in the reaction catalyzed by either isozyme. From the many pyrimidine analogues tested for their binding affinity to each of these isozymes, I-dUrd and Br-dUrd had high good affinity which was equivalent to that of deoxythymidine. 5-Allyl-dUrd, 5-ethyl-dUrd, and 5-propyl-dUrd were only weakly bound to each isozyme. 5-I-dCyd, 5-Br-dCyd, dCyd, and 5-vinyl-dUrd were tightly bound to mitochondrial deoxythymidine kinase but not to the cytoplasmic isozyme. dTTP and I-dUTP are potent inhibitors of the reaction catalyzed by both isozymes. In contrast, dCTP and ara-CTP are potent inhibitors only of the mitochondrial isozyme, but not of the cytoplasmic isozyme. ATP-MG2+ acts as a sigmoidal substrate of the cytoplasmic isozyme with a"Km" of 0.22 mM, and as a regular substrate of the mitochondrial isozyme with a Km of 0.1 mM. Deoxythymidine acts as a regular substrate for both cytoplasmic and mitochondrial isozyme with a Km of 2.6 and 5.2 muM, respectively. Initial velocity as well as product inhibition studies suggest that the cytoplasmic isozyme catalyzes the reaction via a "sequential" mechanism. In contrast, mitochondrial deoxythymidine kinase catalyzes the reaction via a "ping-pong" mechanism.
103 citations
TL;DR: 4-Ethyl-, 5-vinyl, 5-propyl-, and 5-allyl-2′-deoxyuridine (dUrd) had antiviral activity against herpes simplex type 1 and type 2 grown in HeLa TK− cells, but they were inactive against a Tk− mutant of herpes simpleX type 1.
Abstract: 5-Ethyl-, 5-vinyl-, 5-propyl-, and 5-allyl-2'-deoxyuridine (dUrd) had antiviral activity against herpes simplex type 1 and type 2 grown in HeLa TK(-) cells, in the order 5-vinyl-dUrd, 5-ethyl-dUrd, 5-propyl-dUrd, 5-allyl-dUrd, but they were inactive against a TK(-) mutant of herpes simplex type 1. The antiviral activity of these compounds could be partially reversed by thymidine. Except for 5-vinyl-dUrd, they were not toxic to WI-38 and HeLa TK(-) cells at a concentration of 25 muM. All four analogues inhibited the growth of herpes simplex type 1-transformed HeLa TK(-) cells at a concentration of 1 muM.
101 citations
TL;DR: The 5'-amino-2',5'-dideoxy analogs of 5-methyl-, 5-chloro, 5-bromo, and 5-iodo-2'-deoxyuridine possess antiviral activity against herpes simplex virus but exhibit no inhibitory activity against sarcoma 180 (murine) or Vero (monkey) cells in culture.
Abstract: The 5'-O-p-tolylsulfonyl derivatives of 5-chloro-, 5-bromo, and 5-iodo-2'-deoxyuridine were synthesized and converted into the corresponding 5-halo-5'-azido-2',5'-dideoxyuridines (5-7). Reduction of 5-chloro-5'-azido-2',5'-dideoxyuridine (5) afforded 5-chloro-5'-amino-2',5'-dideoxyuridine (10, AClU); however, similar efforts to prepare 5-bromo-5'-amino-2',5'-dideoxyuridine (11) and 5-iodo-5'-amino-2',5'-dideoxyuridine (12) by reduction of the corresponding 5'-azido precursor resulted in the formation of 5'-amino-2',5'-dideoxyuridine (9). 5-Bromo-5'-amino-2',5'-dideoxyuridine (11, ABrU) and 5-iodo-5'-amino-2',5'-dideoxyuridine (12, AIU) were prepared by halogenation of the 5-mercuriacetate of 5'-amino-2',5'-dideoxyuridine. The 5'-amino-2',5'-dideoxy analogs of 5-methyl-, 5-chloro-, 5-bromo-, and 5-iodo-2'-deoxyuridine possess antiviral activity against herpes simplex virus but exhibit no inhibitory activity against sarcoma 180 (murine) or Vero (monkey) cells in culture. 2 tables.
73 citations
TL;DR: Studying on binding of various thymidine analogs with free 5'-OH to these deoxythymidine kinases indicated that 5-substituted ethyl-, vinyl-, allyl-, propyl-, iodo- and bromo-dUrd as well as iodo5 dCyd and arabinosylthymidine had good affinity to both enzymes.
62 citations