Having previously reported on the successful design of selective ) were identified as the most active leads.At this point we decided on the following two-stage strategy in our quest for GPRT ligands.The present study is a continuation of our efforts to use three-dimensional structures of parasitic phosphoribosyltransferases (PRTs) to design novel antiparasitic agents. All protozoan parasites lack the ability to synthesize purine nucleotides de novo.
As a second step in this process, altering the phthalimide moiety to optimize interactions in the guanine-binding pocket of GPRT is expected to lead to compounds with promising activity against Computer-aided drug design in combination with combinatorial chemistry approaches, whereby focused or diverse combinatorial libraries can be designed using computational methods, is becoming increasingly important in the process of drug discovery for parasitic targets (7, 11). Due to a lack of interconversion between the two purine nucleotide pools, either of the two enzymes could serve as a potential target for giardiasis chemotherapy (33).
A number of groups have reported on the successful design of inhibitors directed against trypanosomal (2, 4, 15–16), leishmanial (6), malarial (19), and tritrichomonal (3, 27) targets active in the 10 n M to 50 μM range. GPRT shows little homology with the known sequences of other purine PRTs (26).
Guanine and the tetrasodium salt of PRPP were purchased from Sigma Chemical Co. Louis, Mo.) and are of the highest purity available., and concentrations were determined by integration of nuclear magnetic resonance peaks with methylene chloride as an internal standard. UC_Select (25) in combination with the Daylight version of the Available Chemicals Directory was used to identify original reagent sets, as well as for the elimination of reagents that had unattractive chemical or pharmaceutical properties.
The concentration of dimethyl sulfoxide in the assays was kept at 10%. Similarity and superstructure searches of the Available Chemicals Directory were performed with Daylight's Merlin system (version 4.61; Daylight Chemical Information Systems, Inc., Santa Fe, N.
Two micromolar phthalimide-based GPRT inhibitors were identified by screening the in-house phthalimide library. Inhibitors of PRTs that are able to block purine salvage in vivo could represent an efficient approach to antiparasite chemotherapy (31, 32)., an anaerobic binucleate flagellated protozoan that causes intestinal infection, a condition termed giardiasis in mammals (1), relies primarily on two independent pathways for its nucleotide synthesis.