Polyglutamyl and polylysyl derivatives of the lysine analogues of folic acid and homofolic acid.

A series of Nepsilon-poly-alpha-glutamyl and Nepsilon-polylysyl derivatives of Nalpha-pteroyllysine and Nalpha-homopteroyllysine, analogues of the naturally occurring gamma-polyglutamyl forms of folate, was prepared and tested as substrates for dihydrofolate reductase and as substrates and inhibitors of thymidylate synthetase. Nalpha-Dihydropteroyl-Nepsilon-(tri-alpha-glutamyl)lysine was 1.8 times as active as Nalpha-dihydropteroyl glutamate (dihydrofolate) as a substrate for L1210 murine leukemia dihydrofolate reductase. N-alpha-Dihydropteroyl-Nepsilon-(di-alpha-lysyl)lysine was 1.2 times as active as dihydrofolate in spite of its strong positive charge. The most active compound tested, Nepsilon-(tert-butyloxycarbonyl)lysine, was 3.5 times as active as dihydrofolate. None of the enzymatically prepared Nalpha-tetrahydropteroyllysine derivatives tested was as active as Nalpha-tetrahydropteroyl glutamate (tetrahydrofolate) as a substrate for E. coli thymidylate synthetase. However, there was a progressive increase in activity with the addition of each alpha-glutamyl residue, the Nepsilon-(penta-alpha-glutamyl)lysine being 88% as active as tetrahydrofolate. Nalpha-Tetrahydropteroyl-Nepsilon-(di-alpha-lysyl)lysine was the most active thymidylate synthetase substrate of the polylysine derivatives, being 67% as active as tetrahydrofolate. Addition or deletion of lysyl residues resulted in diminished activity. It is noteworthy that substrate activity is retained in spite of the positively charged poly(amino acid) side chain. None of the enzymatically prepared tetrahydrohomopteroyl derivatives tested was as active as Nalpha-tetrahydrohomopteroyl glutamate (tetrahydrohomofolate) as an inhibitor of E. coli thymidylate synthetase.