Some pathogens, including parasites of the genus Trypanosoma causing Human and Animal African Trypanosomiases, cannot synthesize purines de novo and they entirely rely on the purine salvage pathway (PSP) for their nucleotide generation. Thus, their PSP enzymes are considered as promising drug targets, sparsely explored so far. Recently, a significant role of acyclic nucleoside phosphonates (ANPs) as inhibitors of key enzymes of PSP, namely of 6-oxopurine phosphoribosyltransferases (PRTs), has been discovered. Herein, we designed and synthesized two series of new ANPs branched at the C1' position as mimics of adenosine monophosphate. The novel ANPs efficaciously inhibited Trypanosoma brucei adenine PRT (TbrAPRT1) activity in vitro and it was shown that the configuration on the C1' chiral centre strongly influenced their activity: the (R)-enantiomers proved to be more potent compared to the (S)-enantiomers. Two ANPs, with Ki values of 0.39 μM and 0.57 μM, represent the most potent TbrAPRT1 inhibitors reported to date and they are an important tool to further study purine metabolism in various parasites.
- MeSH
- adeninfosforibosyltransferasa antagonisté a inhibitory metabolismus MeSH
- adenosinmonofosfát chemická syntéza chemie farmakologie MeSH
- antiprotozoální látky chemická syntéza chemie farmakologie MeSH
- inhibitory enzymů chemická syntéza chemie farmakologie MeSH
- molekulární struktura MeSH
- nukleosidy chemická syntéza chemie farmakologie MeSH
- parazitické testy citlivosti MeSH
- Trypanosoma brucei brucei účinky léků enzymologie MeSH
- vztah mezi dávkou a účinkem léčiva MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Publikační typ
- časopisecké články MeSH
Three structurally diverse types of the protected pyrrolidine nucleoside phosphonates were prepared as the monomers for the introduction of pyrrolidine nucleotide units into modified oligonucleotides on the solid phase. Two different chemistries were used for incorporation of modified and natural units: the phosphotriester method for the former, i.e., monomers containing N-phosphonoalkyl and N-phosphonoacyl moieties attached to the pyrrolidine ring nitrogen atom, and phosphoramidite chemistry for the latter. Since the synthesized pyrrolidine nucleoside phosphonic acids are close mimics of the 3'-deoxynucleoside 5'-phosphates, the incorporation of one modified unit into oligonucleotides gives rise to one 2',5' internucleotide linkage. A series of nonamers containing two or three modified units, as well as the fully modified adenine 15-mer, were synthesized in reverse order, i.e., from the 5' to the 3' end of the strand. The measurement of thermal characteristics of the complexes of modified nonamers with the complementary strand revealed a destabilizing effect of the introduced modification. The modified adenine homooligonucleotide, was found to form the most stable complex with oligothymidylate of all the tested modified oligonucleotides in terms of ?Tm per modification.
Recombinant human abacavir monophosphate deaminase (hABC-MP deaminase) was compared with the recently described rat N6-methyl-AMP (meAMP) aminohydrolase. hABC-MP deaminase, a 42 kDa polypeptide, exists predominantly as a monomer under non-denaturing conditions. Similar to the rat enzyme, hABC-MP deaminase efficiently catalyzes the hydrolytic deamination of natural substrates meAMP (5), N6,N6-dimethyl-AMP (13) and medAMP (6). Acyclic nucleoside phosphonate (ANP) N6-cyclopropyl-2,6-diamino-9-[2-(phosphonomethoxy)ethyl]purine (cPrPMEDAP) (1), an intermediate intracellular metabolite of antileukemic agent GS-9219, was effectively converted to the corresponding active guanine analog by hABC-MP deaminase. In addition to cPrPMEDAP (1), a number of other biologically active N6-substituted purine ANPs are alternative substrates for hABC-MP deaminase. The efficiency of their deamination depends on the character of N6-substitution in the adenine and/or 2,6-diaminopurine ring. ANPs with N6-cyclic substituents are deaminated more readily than corresponding compounds with aliphatic substituents of the same length. The deamination of ANPs is also influenced by modifications at the phosphonoalkyl side chain. Among 9-[2-(phosphonomethoxy)propyl] ANPs, (S)-enantiomers are preferred to (R)-enantiomers. Alternatively, the presence of extended 9-[2-(phosphonoethoxy)ethyl] moiety leads to a moderate increase in the reaction velocity compared to cPrPMEDAP (1). Comparison of hABC-MP deaminase and the rat meAMP aminohydrolase across a broad spectrum of N6-substituted substrates revealed a strong correlation of their substrate specificities. Similar to the rat meAMP aminohydrolase, hABC-MP deaminase was highly sensitive to deoxycoformycin monophosphate, but not to the guanine product of cPrPMEDAP (1) deamination. Together, these data demonstrate that hABC-MP deaminase is human meAMP aminohydrolase involved in the intracellular activation of biologically active N6-substituted nucleotide analogs.
