Inhibition of Deoxythymidine Kinase Activity by the Virostatic 5-Ethyl-2′-Deoxyuridine

Abstract

Investigations on deoxythymidine Kinase show that: (a) 5-ethyl-2′-deoxyuridine-β (EDU-β) binds to about 100-fold weaker (K_m 2.7 × 10^-4) than deoxythymidine (K_m 2.5 × 10^-6) and the rate of its phosphoration (0.7 nmol/mg protein/15 min) is about the half of the deoxythymidine (1.52 nmol/mg protein/15 min); (b) 5-ethyl-2′-deoxyuridine-α (EDU-α), 5-propyl-2′-deoxyuridine (α and β) as well as α and β-5-isopropyl-2′- deoxyuridines do not serve as substrates for this enzyme.

Differential Incorporation of Thymidylate Analogues into DNA by DNA Polymerase and by DNA Polymerases Specified by Two Herpes Simplex Viruses

“…Several nucleoside analogues have been used in the therapy of herpes simplex virus (HSV) infection (Gauri, 1979;Gauri & Walter, 1973;Gauri & Malorny, 1967;Kaufmann & Heidelberger, 1964;Kaufmann et aL, 1962;Schabel, 1968). Some nucleoside analogues which are efficiently phosphorylated by cellular kinases and are incorporated into DNA in proliferating cells and tissues show cytotoxic effects in uninfected cells (Gauri et al, 1976;Kit, 1976).…”

“…Other analogues with no or low cytotoxicity show specific antiviral activity due to their selective or increased uptake by HSV-infected cells. HSV-induced pyrimidine kinase phosphorylates these nucleoside analogues more efficiently than the corresponding cellular enzyme (Gauri & Walter, 1973;Cheng et al, 1979;Kit, 1976) resulting in a higher intracellular concentration of the phosphorylated analogues in infected cells. Additionally, herpes viruses code for their own DNA polymerase (Keir et al, 1966;Weissbach et al, 1973).…”

Progress with antiviral agents

“…EtUdR was found to be almost as effective as IUdR and BUdR against vaccinia virus on HeLa cells [46] , and was somewhat less effective than IUdR against herpes simplex on chick embryo fibroblast monolayers (H. Kaufman, personal communication). Other reports of activities against these viruses are even more promising ( [47] and references therein), and further trials are now under way with Dr. E. DeClercq. Meanwhile S-ethyl-2'-deoxycytidine has been synthesized [48]; in tests conducted by DeClercq against herpes,.vaccinia and VSV viruses on primary rabbit kidney cells, it exhibited weak activity only against herpes, probably via cellular deamination to the active EtUdR [48].…”

“…The low incorporation of S-ethyluracil into E. coli DNA (about 15% replacement of thymine) is due in part to its poor properties as a substrate of thymidine phosphorylase. EtUdR is a moderate inhibitor of thymidine kinase and is itself a poorer substrate than thymidine [47]. Muraoka and Ueda [49] have synthesized 5-ethyluracil-1 -fl-D-galactopyranoside and the corresponding xylopyranoside, both of which were claimed to exhibit appreciable activity against the Mahoney strain of polio virus.…”

Differential Substrate Specificity of DNA Polymerase beta and of a DNA Polymerase Induced by Herpes Simplex Virus Type 2 towards Thymidine Triphosphate Analogues

“…A number of thymidine analogues have been used in the treatment of herpes simplex virus (HSV) infections (Kaufman et al, 1962;Kaufman & Heidelberger, 1964;Gauri & MaMmy, 1967;Schabel, 1968;Gauri & Walter, 1973;Prusoff& Ward, 1976;Elion et al, 1977;Gentry et al, 1979). Some nucleoside analogues are efficiently phosphorylated by cellular kinases and are incorporated into the DNA of proliferating cells.…”