- Differences in kinetic properties of pure recombinant human and mouse deoxycytidine kinase
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Human and mouse deoxycytidine kinase (dCK) (EC 2.7.1.74) were cloned and expressed in Escherichia coli. Michaelis-Menten kinetics were determined for the purified enzymes with 2'-deoxycytidine (dCyd), 2'-deoxyadenosine (dAdo), 2-chloro-2'-deoxyadenosine (CdA), 2',3'dideoxycytidine (ddCyd) and 9-β-D-arabinofuranosylguanine (araG) as substrates and ATP and UTP as phosphate donors. Both human and mouse dCK showed highest affinity to dCvd with K(m) values of 0.05-0.2 μM. The anti-leukaemic compound CdA was the superior substrate of the nucleoside analogues tested. Both enzymes were able to efficiently utilize ATP and UTP as phosphate donors. However, the use of UTP instead of ATP as phosphate donor decreased K(m) values for all substrates investigated. The kinetic properties of mouse and human dCK differed in that the human enzyme showed higher affinity for the substrates dAdo, CdA, ddCyd and araG. The human enzyme also showed higher affinity for ATP and UTP. The ability to phosphorylate dCyd was, however, similar for both human and mouse dCK. At physiological concentration of the feedback inhibitor dCTP, mouse dCK showed lower activity than human dCK for all substrates investigated.
- Johansson, Magnus,Karlsson, Anna
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p. 163 - 168
(2007/10/03)
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- A convenient synthesis of 2'-deoxy-6-thioguanosine, ara-guanine, ara-6-thioguanine and certain related purine nucleosides by the stereospecific sodium salt glycosylation procedure [1]
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A simple and high-yield synthesis of biologically significant 2'-deoxy-6-thioguanosine, ara-6-thioguanine and araG has been accomplished employing the stereospecific sodium salt glycosylation method. Glycosylation of the sodium salt of 6-chloro- and 2-amino-6-chloropurine (1 and 2, respectively) with 1-chloro-2-deoxy-3,5-di-O-(p-toluoyl)-α-D-erythro-pentofuranose gave the corresponding N-9 substituted nucleosides as major products with the β-anomeric configuration (4 and 5, respectively) along with a minor amount of the N-7 positional isomers (6 and 7). Treatment of 4 with hydrogen sulfide in methanol containing sodium methoxide gave 2'-deoxy-6-thioinosine in 93% yield. Similarly, 5 was transformed into 2'-deoxy-6-thioguanosine (β-TGdR, 11) in 71% yield. Reaction of the sodium salt of 2 with 1-chloro-2,3,5-tri-O-benzyl-α-D-arabinofuranose gave N-7 and N-9 glycosylated products 13 and 9, respectively. Debenzylation of 9 with boron trichloride at -78° gave the versatile intermediate 2-amino-6-chloro-9-β-D-arabinofuranosylpurine 62% yield. Direct treatment of 14 with sodium hydrosulfide furnished ara-6-thioguanine. Alkaline hydrolysis of 14 readily gave 9-β-D-arabinofuranosylguanine (araG, 17), which on subsequent phosphorylation with phosphorus oxychloride in trimethyl phosphate afforded araG 5'-monophosphate.
- Hanna,Ramasamy,Robins,Revankar
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p. 1899 - 1903
(2007/10/02)
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