Conversion of pteroylglutamic acid to the citrovorum factor by preparations from Lactobacillus casei.

The conversion of folic acid to citrovorum factor (N5-formyl tetrahydrofolic acid) had been demonstrated for preparations of Streptococcusfaecalis (Broquist et al., 1953), Lactobacillus arabinosus (Hendlin et al., 1953), Lactobacillus casei (Bond, 1953), and a number of animal tissues (Winsten and Eigen, 1950; Nichol and Welch, 1950; Nichol, 1952). It has been shown that ascorbic acid, ATP,3 Mg+, DPN, and a source of a one-carbon unit (Nichol, 1954) are required for optimal conversion of folic acid to citrovorum factor or to an active formylating form of this vitamin. Pyridoxal phosphate, Mn, and TPN (Jaenicke, 1956) have been reported as needed for a one-carbon donor system involving serine. We wish to report the requirement of another cofactor for the conversion of folic acid to citrovorum factor by a preparation of L. casei, which is found in the boiled extract of crude enzyme preparations.