10-(2-benzoxazolcarbonyl)-5,10-dideaza-acyclic-5,6,7,8-tetrahydrofolic acid: a potential inhibitor of GAR transformylase and AICAR transformylase

From Bioorganic Models to Cells

I endeavor to share how various choices-some deliberate, some unconscious-and the unmistakable influence of many others shaped my scientific pursuits. I am fascinated by how two long-term, major streams of my research, DNA replication and purine biosynthesis, have merged with unexpected interconnections. If I have imparted to many of the talented individuals who have passed through my lab a degree of my passion for uncloaking the mysteries hidden in scientific research and an understanding of the honesty and rigor it demands and its impact on the world community, then my mentorship has been successful.

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.

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

The synthesis and 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 (2) as an inhibitor of glycinamide ribonucleotide transformylase (GAR Tfase) and aminoimidazole carboxamide ribonucleotide transformylase (AICAR Tfase) are reported. The inhibitor 2 was prepared in a convergent synthesis involving C-alkylation of methyl 4-(4,4,4-trifluoro-3-dimethylhydrazonobutyl)benzoate with 1-chloro-3-iodopropane followed by construction of the pyrimidinone ring. Compound 2 was found to be an effective inhibitor of recombinant human GAR Tfase (K(i) = 0.50 microM), whereas it was inactive (K(i) > 100 microM) against E. coli GAR Tfase as well as recombinant human AICAR Tfase. Compound 2 exhibited modest, purine-sensitive growth inhibitory activity against the CCRF-CEM cell line (IC50 = 6.0 microM).

Design, synthesis, and biological evaluation of 10-methanesulfonyl-DDACTHF, 10-methanesulfonyl-5-DACTHF, and 10-methylthio-DDACTHF as potent inhibitors of GAR Tfase and the de novo purine biosynthetic pathway

The synthesis and evaluation of 10-methanesulfonyl-DDACTHF (1), 10-methanesulfonyl-5-DACTHF (2), and 10-methylthio-DDACTHF (3) as potential inhibitors of glycinamide ribonucleotide transformylase (GAR Tfase) and aminoimidazole carboxamide ribonucleotide transformylase (AICAR Tfase) are reported. The compounds 10-methanesulfonyl-DDACTHF (1, K(i) = 0.23 microM), 10-methanesulfonyl-5-DACTHF (2, K(i) = 0.58 microM), and 10-methylthio-DDACTHF (3, K(i) = 0.25 microM) were found to be selective and potent inhibitors of recombinant human GAR Tfase. Of these, 3 exhibited exceptionally potent, purine sensitive growth inhibition activity (3, IC50 = 100 nM) against the CCRF-CEM cell line being 3-fold more potent than Lometrexol and 30-fold more potent than the parent, unsubstituted DDACTHF, whereas 1 and 2 exhibited more modest growth inhibition activity (1, IC50 = 1.0 microM and 2, IC50 = 2.0 microM).