Inhibition of thymidylate synthetase and dihydrofolate reductase by naturally occurring oligoglutamate derivatives of folic acid.

Naturally occurring oligoglutamate derivatives of folic acid in extracts of Escherichia coli have been isolated on the basis of their inhibitory actions toward thymidylate synthetase and dihydrofolate reductase. The inhibitor of thymidylate synthetase has been identified as N-5-formyl-H4pteroyloligoglutamate (approximately 5 amino acid residues). It is 150-fold more inhibitory than the monoglutamate.