Drug design of selective 5'-nucleotidases inhibitors

Petr Pachl¹⁾, Jiří Brynda^1,2), Ivan Rosenberg ²⁾, Milan Fábry¹⁾, Pavlína Řezáčová^1,2),

¹⁾Institute of Molecular Genetics, Flemingovo nam. 2, Prague 6, Prague, 16610, Czech Republic, ²⁾Institute of Organic Chemistry and Biochemistry AS CR, Flemingovo nam. 2, Prague 6, Prague, 16610, Czech Republic, Email: petr.pachl@img.cas.cz

The monophosphate 5'-nucleotidases, including 5'(3')-deoxyribonucleotidase, belong to a family of enzymes that catalyze the dephosphorylation of nucleoside monophosphates. The ribonucleotides and deoxyribonucleotides could be synthesized de novo from low-molecular-weight precursors or by salvage from nucleosides or nucleobases coming from catabolism of nucleic acids[1]. In this salvage pathway, ribonucleotides and deoxyribonucleotides are phosphorylated by nucleoside and nucleotide kinases to maintain sufficient pools of dNTP's and NTP's for synthesis of DNA and RNA. The phosphorylation by cellular nucleoside kinases is opposed by 5'-nucleotidases that dephosphorylate ribo- and deoxyribonucleoside monophosphates[2,3,4]. Besides their role in the regulation of physiological dNTP pools, substrate cycles between ribonucleotidases and kinases may affect the therapeutic action of pyrimidine nucleoside analogs used as anticancer and antiviral agents. Such compounds require the nucleoside kinases activity for phosphorylation to their active forms. Results of clinical and in vitro studies propose that an increase in nucleotidase activity can interfere with nucleoside analogue activation resulting in drug resistance[5].

The main goal of this project is the search for potent and selective inhibitors of mammalian 5'-nucleotidases based on nucleoside phosphonic acids and their derivatives and comparison of sensitivity of 5'-nucleotidases isolated from various sources toward individual inhibitors.

We have prepared 2 types of human 5'-nucleotidase: cytosolic and mitochondrial by recombinant expression in E. coli. The inhibitory properties of a series of nucleoside phosphonic acids derivatives are tested and for the most promising compounds the enzyme-inhibitor structure will be determined to serve as a lead for structure-based drug design efforts.

In general, compounds of strong and selective inhibitory potency are of high medicinal interest as antimetabolites for anticancer and antiviral therapy.

[1] P. Reichard: Interactions between deoxyribonucleotide and DNA synthesis. Annu Rev Biochem., 57 (1988), 349-74.

[2] S.A. Hunsucker, B.S. Mitchell, J. Spychala: The 5'-nucleotidases as regulators of nucleotide and drug metabolism. Pharmacol Ther., 107 (2005), 1-30.

[3] V. Bianchi, E. Pontis, P. Reichard: Interrelations between substrate cycles and de novo synthesis of pyrimidine deoxyribonucleoside triphosphates in 3T6 cells. Proc Natl Acad Sci U S A, 83 (1986), 986-90.

[4] P. Bianchi, E. Fermo, F. Alfinito, C. Vercellati, M. Baserga, F. Ferraro, I. Guzzo, B. Rotoli, A. Zanella: Molecular characterization of six unrelated Italian patients affected by pyrimidine 5'-nucleotidase deficiency. Br J Haematol, 122 (2003), 847-51.

[5] C. Mazzon, C. Rampazzo, M.C. Scaini, L. Gallinaro, A. Karlsson, C. Meier, J. Balzarini, P. Reichard, V. Bianchi: Cytosolic and mitochondrial deoxyribonucleotidases: activity with substrate analogs, inhibitors and implications for therapy. Biochem Pharmacol, 66 (2003), 471-9.

Figure 1. X-ray structure structure of human cytosolic 5'-nucleotidase with catalytic magnesium ion represented

as a cyan sphere and modeled dGMP shown in stick model with yellow carbon atoms.