Inhibition of human folylpolyglutamate synthetase by diastereomeric phosphinic acid mimics of the tetrahedral intermediate

Abstract

Phosphorus-containing pseudopeptides, racemic at the C-terminal α-carbon, are potent mechanismbased inhibitors of folylpolyglutamate synthetase (FPGS). They are mimics of the tetrahedral intermediate postulated to form during FPGS-catalyzed biosynthesis of poly(γ-L-glutamates). In the present paper, the FPGS inhibitory activity of each diastereomer coupled to three heterocycles is reported. The high R f pseudopeptide containing the 5,10-dideazatetrahydropteroyl (DDAH 4 Pte) heterocycle is most potent (K is = 1.7 nM). While the heterocyclic portion affects absolute FPGS inhibitory potency, the high R f species is more potent in each pair containing the same heterocycle. This species presumably has the same stereochemistry as the natural folate polyglutamate, i.e., (LGlu-γ-L-Glu). Unexpectedly, the low R f (presumed L-Glu-γ-D-Glu) species are only slightly less potent (<30-fold) less potent than their diastereomers. Further study of this phenomenon comparing L-Glu-γ-L-Glu and L-Glu-γ-D-Glu dipeptide-containing FPGS substrates shows that <1% contamination of commercial D-Glu precursors by L-Glu may give misleading information if L-Glu-γ-L-Glu substrates have low K m values.

Molecular Dynamics Reveal Binding Mode of Glutathionylspermidine by Trypanothione Synthetase

“…2C) known to inhibit GspS as well as TryS [43]. This type of phosphorous-containing pseudopeptides has widely been used to mimic the transition state of peptide bond formation by ATP-dependent ligases [23], [42]–[44] and disclose the approximate position of the γ-phosphate of ATP and, in case of TryS, the productive binding poses of the GSH to be phosphorylated and the Sp to be acylated. Visual inspection of protein conformation snapshots created by molecular dynamics simulation revealed stable conformations and positions of ADP and both Mg 2+ ions in the respective binding pocket.…”

Synthesis and Biological Applications of Phosphinates and Derivatives

“…These results suggest -with current knowledge of FPGS stereospecificity -that the high Rf species is likely analogous to the natural L-Glu-ψ-L-Glu configuration. Nevertheless, the best inhibition observed with the phosphinic acid mimics series, was supported by the isomer 92a1 (high Rf) with an IC 50 of 1.7 AE 0.2 nM [90].…”

“…For both isomers 93a1 and 93a2, they were accessible by mixing pteroyl azide 95 and Glu-γ-Glu-γ[ψ{P(O)(OH)-CH 2 }glutarate phosphinic acid pseudotripeptide (pure isomer) [89]. Among separate diastereomeric pairs of 90a, 91a, 92a and 93a, diastereomers having a high Rf (HPLC) gave a better inhibition of the recombinant human cytosolic FPGS [90]. For instance, the compound 90a1 (high Rf) was about 13-fold (IC 50 ¼ 3.5 AE 0.3 nM) more potent than the diastereomer 90a2 with low Rf (IC 50 ¼ 45 AE 0.3 nM), and about fourfold more efficient than original mixture of the four diastereomers 90 (IC 50 ¼ 13.6 AE 1.3 nM).…”

“…The free carboxylic acids were then esterified by diazomethane. The complete deprotection of the esters 103a and 103b was carried out under strong acid conditions to afford the pseudopeptides 94a and 94b in excellent yields (Scheme 21) [90].…”

“…16). For the preparation of targeted molecules, each phosphinate diastereomer has been prepared individually and was coupled with three different heterocycles: 4-amino-4-deoxy-10-methylpteroate [89], pteroate [90] and 5,10-dideazatetrahydropteroate [90]. For example, both diastereomers under salt form 90a1 and 90a2 (Scheme 21) [89] were prepared by coupling pure diastereomer pseudopeptide 94a or 94b with acyl azide 95, AMPte-N 3 , derived from 4-amino-4-deoxy-10-methylpteroic acid [91], using the strategy described [87].…”