Collect. Czech. Chem. Commun. 2008, 73, 275-291

Human N6-Methyl-AMP/DAMP Aminohydrolase (Abacavir 5'-Monophosphate Deaminase) is Capable of Metabolizing N6-Substituted Purine Acyclic Nucleoside Phosphonates

Markéta Schinkmanováa,*, Ivan Votrubaa, Riri Shibatab, Bin Hanb, Xiaohong Liub, Tomas Cihlarb and Antonín Holýa

a Gilead Sciences Research Center, Institute of Organic Chemistry and Biochemistry, v.v.i., Academy of Sciences of the Czech Republic, 166 10 Prague 6, Czech Republic
b Gilead Sciences, Foster City, CA 94404, U.S.A.


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.

Keywords: Abacavir 5'-phosphate; N6-Methyl-AMP aminohydrolase; 2,6-Diaminopurine; Guanine; Acyclic nucleoside phosphonates; Prodrugs; cPrPMEDAP.

References: 22 live references.