Synthesis of a compound with folic acid activity by Lactobacillus arabinosus 17-5

Summary A compound with folic acid activity is synthesized by growing as well as respiring cells of Lactobacillus arabinosus in the presence of p-aminobenzoic acid. The essentiality of glutamic acid is seen in studies with respiring cells.The free folic acid activity elaborated by Lactobacillus arabinosus reaches its maximum in about 48 hrs. and is present mainly in the culture filtrate.Additions of Tween 80, or biotin and of xanthine show marked stimulation of the synthesis of folic acid activity.With the organisms Streptococcus faecalis R and Lactobacillus casei, requiring exogenous folic acid for growth, it is seen that the entire folic acid activity resides in the cells and as citrovorum factor.Sulphanilamide inhibits the synthesis of folic acid activity by Lactobacillus arabinosus.     

Synthesis of a substance exhibiting citrovorum factor activity by Lactobacillus arabinosus 17-5

Summary Growing and respiring cells of Lactobacillus arabinosus elaborate citrovorum factor activity from p-aminobenzoic acid. Pteroylglutamic acid is a step in this conversion.That the activity synthesized is apparently different from the citrovorum factor is inferable from observations on inhibition analysis, differential distribution between immiscible solvents at various p_H and bioautographic studies.Ascorbic acid aids in the synthesis of citrovorum factor active substance. Formate and formyl precursors have stimulatory effect on this synthesis but only in presence of ascorbic acid.     

The synthesis of folic acid-like compounds by Lactobacillus arabinosus

In the presence of p-aminobenzoic acid (PABA), Lactobacillus arabinosus synthesizes one or more compounds with folic acid (FA)-like activity during growth. The total FA activity formed is proportional to the amount of PABA added, up to 200 mμg./tube. Most of the FA activity is in a bound form which is present chiefly in the cells, and the remainder is present in free form which is mainly in the culture medium. Increasing levels of sulfanilamide in the medium competitively inhibit the utilization of PABA for growth of L. arabinosus and decrease the amount of free and combined FA compounds formed.Equimolecular amounts of p-aminobenzoylglutamic acid and PABA have approximately the same growth-promoting and antisulfanilamide activities for L. arabinosus under the conditions employed, and lead to the synthesis of similar amounts of the FA-like compound by L. arabinosus.Thymidine can replace PABA for growth of L. arabinosus and its activity is inhibited very little by sulfanilamide. Thymine and thymidylic acid are much less effective than thymidine. Crystalline vitamin B_c conjugate and vitamin B₁₂ cannot replace PABA for growth of L. arabinosus and do not augment the antisulfonamide activity of PABA.The growth-promoting and antisulfanilamide activities of synthetic folid acid (pteroylglutamic acid), citrovorum factor, and formylfolic acid preparations for L. arabinosus are much poorer than those of equimolecular amounts of PABA. The possibility that the compound(s) with FA-like activity produced by L. arabinosus may differ from pteroylglutamic acid, citrovorum factor, or formylfolic acid is discussed.