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Antimicrobial Agents and Chemotherapy, 10 1995, 2304-2308, Vol 39, No. 10
BL Robbins, J Greenhaw, MC Connelly and A Fridland
9-(2-Phosphonylmethoxyethyl)adenine (PMEA), the acyclic phosphonate analog
of adenine monophosphate, is a promising antiviral drug with activity
against herpesviruses, Epstein-Barr virus, and retroviruses, including the
human immunodeficiency virus. In order to be active, it must be converted
to the diphosphate derivative, the putative inhibitor of viral DNA
polymerases. The metabolic pathway responsible for activation of PMEA is
unclear. The metabolism of PMEA was investigated in human T-lymphoid cells
(CEMss) and a PMEA-resistant subline (CEMss(r- 1)) with a partial
deficiency in adenylate kinase activity. Experiments with [3H]PMEA showed
that extracts of CEMss phosphorylated PMEA to its mono- and diphosphate in
the presence of ATP as the phosphate donor. No other nucleotides or
5-phosphoribosyl pyrophosphate displayed appreciable activity as a
phosphate donor. Subcellular fractionation experiments showed that CEMss
cells contained two nucleotide kinase activities, one in mitochondria and
one in the cytosol, which phosphorylated PMEA. The PMEA-resistant CEMss
mutant proved to have a deficiency in the mitochondrial adenylate kinase
activity, indicating that this enzyme was important in the phosphorylation
of PMEA. Other effective antiviral purine phosphonate derivatives of PMEA
showed a profile of phosphorylating activity similar to that of PMEA. By
comparison, phosphorylation of the pyrimidine analog (S)-1-(3-hydroxy-2-
phosphonylmethoxypropyl) cytosine proceeded by an enzyme present in the
cytosol. We conclude from these studies that adenylate kinase which has
been localized in the intermembrane space of mitochondria is the major
route for PMEA phosphorylation in CEMss cells but that another hitherto
unidentified enzyme(s) present in the cytosol may contribute to the
anabolism of the phosphonates.
Copyright © 1995 by the American Society for Microbiology. All rights reserved.
Metabolic pathways for activation of the antiviral agent 9-(2- phosphonylmethoxyethyl)adenine in human lymphoid cells
Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
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