Microbial Synthesis of Folate Polyglutamates from Labelled Precursors

SUMMARY: The uptake and synthesis of folate polyglutamates from [3H]pteroylglutamic acid and [14C]p-aminobenzoic acid was studied in Lactobacillus casei, Streptococcus faecalis, L. plantarum and Escherichia coli. The analytical techniques were based on oxidative or hydrolytic degradation of the folate compounds followed by chromatographic separation of the resulting mixtures of pteroylglutamate derivatives or p-aminobenzoylpoly-γ-l-glutamates and comparison with appropriate synthetic standards. All four organisms synthesized numerous polyglutamate derivatives from the precursors provided. The large majority (85 to 95%) of folates of lactobacilli were polyglutamates with more than seven glutamyl residues; L. casei formed several such unidentified long-chain components. In contrast, E. coli and particularly S. faecalis synthesized mainly polyglutamates with seven or less glutamate residues; tetra-, hexa- and heptaglutamates were tentatively identified in E. coli, and tri-, tetra- and pentaglutamates in S. faecalis. While L. casei appeared to synthesize a mixture of formyl- and methyltetrahydro derivatives, formyltetrahydro derivatives predominated in E. coli and S. faecalis.