Inhibition of human folylpolyglutamate synthetase by diastereomeric phosphinic acid mimics of the tetrahedral intermediate.
Phosphorus-containing pseudopeptides, racemic at the C-terminal alpha-carbon, are potent mechanism-based inhibitors of folylpolyglutamate synthetase (FPGS). They are mimics of the tetrahedral intermediate postulated to form during FPGS-catalyzed biosynthesis of poly(gamma-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., (l-Glu-gamma-l-Glu). Unexpectedly, the low R(f) (presumed l-Glu-gamma-d-Glu) species are only slightly less potent (<30-fold) than their diastereomers. Further study of this phenomenon comparing l-Glu-gamma-l-Glu and l-Glu-gamma-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-gamma-l-Glu substrates have low K(m) values.
McGuire
John J
JJ
Grace Cancer Drug Center, Roswell Park Cancer Institute, Buffalo, NY 14263, USA. John.McGuire@RoswellPark.edu
Bartley
David M
DM
Tomsho
John W
JW
Haile
William H
WH
Coward
James K
JK
D003600:Cytosol / Q000201:enzymology; D005492:Folic Acid / Q000378:metabolism; D043425:Glutamate Carboxypeptidase II / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D005971:Glutamates / Q000378:metabolism; D006801:Humans; D020128:Inhibitory Concentration 50; D007700:Kinetics; D015394:Molecular Structure; D010453:Peptide Synthases / Q000037:antagonists & inhibitors* / Q000235:genetics; D010721:Phosphinic Acids / Q000378:metabolism*; D011549:Pseudomonas / Q000201:enzymology / Q000235:genetics; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors; D012995:Solubility; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D011623:gamma-Glutamyl Hydrolase / Q000302:isolation & purification / Q000378:metabolism
D005971:Glutamates; D010721:Phosphinic Acids; D011994:Recombinant Proteins; D005492:Folic Acid; D043425:Glutamate Carboxypeptidase II; D011623:gamma-Glutamyl Hydrolase; D010453:Peptide Synthases; C023103:folylpolyglutamate synthetase