Folate Coenzymes of Lactobacillus casei and Streptococcus faecalis

During growth in the presence of 10 ng of [3H]pteroylglutamic acid (PteGlu) per ml of medium, Lactobacillus casei (ATCC 7469) incorporated 80 to 90% and Streptococcus faecalis (ATCC 8043) 40 to 60% of the added radioactivity. Folate compounds in L. casei were identified as reduced derivatives of PteGlu9 (∼19%), of PteGlu8 (∼42%), of PteGlu7 (∼14%), and PteGlu6 (∼8%); in S. faecalis as reduced derivatives of PteGlu5 (∼24%), of PteGlu4 (∼61%), and PteGlu3 (∼4%). After treatment of cell extracts with hog kidney conjugase ∼39% of folate compounds in L. casei were converted to tetrahydrofolic acid (H4PteGlu), ∼26% to 5-methyl-H4PteGlu and ∼10% to 5- and 10-formyl-H4PteGlu; in the case of S. faecalis ∼25% were converted to H4PteGlu and ∼45% to 5- and 10-formyl-H4PteGlu. No 5-methyl-H4PteGlu derivatives could be found in S. faecalis. Simple methods for the preparation and separation of the biologically active forms of 5-methyl-[3H]H4PteGlu and 5-formyl-[3H]H4PteGlun (n = 1 to 9 glutamic acid residues) with a high specific radioactivity are described. Growth of L. casei in the presence of 100 ng of PteGlu-[U-14C]Glu-Glu or 100 ng of PteGlu3-[U-14C]Glu-Glu per ml of medium was the same as in the presence of 100 ng of PteGlu per ml. PteGlu5 (100 ng per ml of medium) did not inhibit the uptake of [3H]PteGlu (0.3 ng per ml of medium), in contrast to PteGlu3 (100 ng per ml) and PteGlu (100 ng per ml). L. casei converted PteGlu-[U-14C]Glu and PteGlu3-[U-14C]Glu-Glu to the same metabolites as [3H]PteGlu without loss of the 14C label.