Synthesis and biological evaluation of N-[4-[5-(2,4-diamino-6-oxo-1,6-dihydropyrimidin-5-yl)-2-(2,2,2-trifluoroacetyl)pentyl]benzoyl]-L-glutamic acid as a potential inhibitor of GAR Tfase and the de novo purine biosynthetic pathway

Recent advances in the synthesis of fluorinated hydrazones

Fluorinated compounds are widely used in pharmaceuticals, agrochemicals, and materials.

Application of universal stress proteins in probing the dynamics of potent degraders in complex terephthalate metagenome

The culture-independent strategies to study microbial diversity and function have led to a revolution in environmental genomics, enabling fundamental questions about the distribution of microbes and their influence on bioremediation to be addressed. In this research we used the expression of universal stress proteins as a probe to determine the changes in degrading microbial population from a highly toxic terephthalate wastewater to a less toxic activated sludge bioreactor. The impact of relative toxicities was significantly elaborated at the levels of genus and species. The results indicated that 23 similar prokaryotic phyla were represented in both metagenomes irrespective of their relative abundance. Furthermore, the following bacteria taxa Micromonosporaceae, Streptomyces, Cyanothece sp. PCC 7822, Alicyclobacillus acidocaldarius, Bacillus halodurans, Leuconostoc mesenteroides, Lactococcus garvieae, Brucellaceae, Ralstonia solanacearum, Verminephrobacter eiseniae, Azoarcus, Acidithiobacillus ferrooxidans, Francisella tularensis, Methanothermus fervidus, and Methanocorpusculum labreanum were represented only in the activated sludge bioreactor. These highly dynamic microbes could serve as taxonomic biomarkers for toxic thresholds related to terephthalate and its derivatives. This paper, highlights the application of universal stress proteins in metagenomics analysis. Dynamics of microbial consortium of this nature can have future in biotechnological applications in bioremediation of toxic chemicals and radionuclides.

Biological and structural evaluation of 10R- and 10S-methylthio-DDACTHF reveals a new role for sulfur in inhibition of glycinamide ribonucleotide transformylase

Glycinamide ribonucleotide transformylase (GAR Tfase) is a folate-dependent enzyme in the de novo purine biosynthesis pathway, which has long been considered a potential target for development of anti-neoplastic therapeutics. Here we report the biological and X-ray crystallographic evaluations of both independent C10 diastereomers, 10S- and 10R-methylthio-DDACTHF, bound to human GAR Tfase, including the highest-resolution apo GAR Tfase structure to date (1.52 Å). Both diastereomers are potent inhibitors (Ki = 210 nM for 10R, and Ki = 180 nM for 10S) of GAR Tfase and exhibit effective inhibition of human leukemia cell growth (IC₅₀ = 80 and 50 nM, respectively). Their inhibitory activity was surprisingly high, and these lipophilic C10-substituted analogues show distinct advantages over their hydrophilic counterparts, most strikingly in retaining potency in mutant human leukemia cell lines that lack reduced folate carrier protein activity (IC₅₀ = 70 and 60 nM, respectively). Structural characterization reveals a new binding mode for these diastereoisomers, in which the lipophilic thiomethyl groups penetrate deeper into a hydrophobic pocket within the folate-binding site. In silico docking simulations of three other sulfur-containing folate analogues also indicate that this hydrophobic cleft represents a favorable region for binding lipophilic substituents. Overall, these results suggest sulfur and its substitutions play an important role in not only the binding of anti-folates to GAR Tfase but also the selectivity and cellular activity (growth inhibition), thereby presenting new possibilities for the future design of potent and selective anti-folate drugs that target GAR Tfase.

Synthesis of trifluoromethyl ketones via tandem Claisen condensation and retro-Claisen C-C bond-cleavage reaction

A highly efficient, operationally simple approach to trifluoromethyl ketones has been developed that builds on the use of a tandem process involving Claisen condensation and retro-Claisen C-C bond cleavage reaction. Enolizable alkyl phenyl ketones were found to react readily with ethyl trifuoroacetate under the promotion of NaH to afford trifluoroacetic ester/ketone exchange products, trifluoromethyl ketones, which were quite different from the general Claisen condensation products, β-diketones. This procedure uses readily available starting materials and can be extended to the preparation of perfluoroalkyl ketones in excellent yield.

Asymmetric synthesis of inhibitors of glycinamide ribonucleotide transformylase

Glycinamide ribonucleotide transformylase (GAR Tfase) catalyzes the first of two formyl transfer steps in the de novo purine biosynthetic pathway that require folate cofactors and has emerged as a productive target for antineoplastic therapeutic intervention. The asymmetric synthesis and evaluation of the two diastereomers of 10-methylthio-DDACTHF (10R-3 and 10S-3) and related analogues as potential inhibitors of GAR Tfase are reported. This work, which defines the importance of the C10 stereochemistry for this class of inhibitors of GAR Tfase, revealed that both diastereomers are potent inhibitors of rhGAR Tfase (10R-3 Ki = 210 nM, 10S-3 Ki = 180 nM) that exhibit effective cell growth inhibition (CCRF-CEM IC50 = 80 and 50 nM, respectively), which is dependent on intracellular polyglutamation by folylpolyglutamate synthetase (FPGS) but not intracellular transport by the reduced folate carrier.

Human glycinamide ribonucleotide transformylase: active site mutants as mechanistic probes

Human glycinamide ribonucleotide transformylase (GART) (EC 2.1.2.2) is a validated target for cancer chemotherapy, but mechanistic studies of this therapeutically important enzyme are limited. Site-directed mutagenesis, initial velocity studies, pH-rate studies, and substrate binding studies have been employed to probe the role of the strictly conserved active site residues, N106, H108, and D144, and the semiconserved K170 in substrate binding and catalysis. Only two conservative substitutions, N106Q and K170R, resulted in catalytically active enzymes, and these active mutant enzymes gave pH-rate profiles and a steady-state kinetic mechanism essentially identical to those of the native enzyme. All inactive mutants were able to bind both substrates, ruling out disrupted formation of the ternary complex as the source of inactivity. Differences between human and Escherichia coli GART, previously used as a model for the human enzyme, were evident.