Potent inhibition of human folylpolyglutamate synthetase by a phosphinic acid mimic of the tetrahedral reaction intermediate.
A phosphorous-containing pseudopeptide folate analog (Valiaeva et al., J Org Chem 2001;66:5146-54) was designed to mimic the tetrahedral intermediate formed in the ATP-dependent reaction catalyzed by folylpolyglutamate synthetase (FPGS). This analog, methotrexate-phosphinate (MTX-phosphinate; 4-amino-4-deoxy-10-methylpteroyl-L-Glu-gamma-[psi(P(O)(OH)-CH(2))]glutarate), is a highly potent (K(is), 3.1+/-0.5 nM), competitive inhibitor of recombinant human cytosolic FPGS. Within experimental limits, FPGS inhibition was not time-dependent, and preincubation of FPGS, inhibitor, and ATP did not potentiate the inhibition. These results suggest that slow phosphorylation to produce a more potent inhibitor form is not involved. MTX-phosphinate was not growth inhibitory to human CCRF-CEM leukemia cells at 1 microM (70-fold above the concentration of MTX giving 50% growth inhibition), probably because of poor transport. Because of its exceedingly high potency as an FPGS inhibitor, MTX-phosphinate represents a lead structure from which cell-permeable analogs may be developed to test the hypothesis that FPGS inhibition is therapeutically efficacious.
McGuire
John J
JJ
Grace Cancer Drug Center, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263, USA. John.McGuire@RoswellPark.edu
Haile
William H
WH
Valiaeva
Nadya
N
Bartley
David
D
Guo
Jianxia
J
Coward
James K
JK
D002455:Cell Division / Q000187:drug effects; D005493:Folic Acid Antagonists / Q000494:pharmacology*; D006801:Humans; D008727:Methotrexate / Q000494:pharmacology; D010453:Peptide Synthases / Q000037:antagonists & inhibitors*; D010721:Phosphinic Acids / Q000737:chemistry / Q000494:pharmacology*; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism; D014407:Tumor Cells, Cultured
D005493:Folic Acid Antagonists; D010721:Phosphinic Acids; D013762:Tetrahydrofolate Dehydrogenase; D010453:Peptide Synthases; C023103:folylpolyglutamate synthetase; D008727:Methotrexate