Pteroylpoly(gamma-glutamate) synthesis by Corynebacterium species. In vivo synthesis of folates.

Corynebacterium sp. synthesizes pteroylpolyglutamates which are excreted into its growth medium. The major intracellular folates were identified as 10-formyltetrahydro-, 5-formyltetrahydro-, tetrahydro-, and 10-formylpteroyltetraglutamates. The major folates in the medium were identified as 10-formylpteroyltri- and tetraglutamates. p-Aminobenzoic was metabolized to these compounds without any appreciable buildup of pteroylmono- or diglutamate derivatives. The rate-limiting steps in the elongation of the glutamate chain of folate derivatives appear to be at the level of formation of a pteroate derivative and at the pteroyltetraglutamate level.