LIPID STORAGE UNDER ABNORMAL CONDITIONS 653 



Nichol and Welch 669 suggested that the mechanism which accounts for 

 the inhibitory action of aminopterin toward folic acid may consist in pre- 

 venting its conversion to CF (LCF) (Leuconostoc citrovorum factor) . LCF 

 is considered to be the active form of folic acid. Sauberlich and Bau- 

 mann 670 first presented evidence for this factor, based upon microbiological 

 assays. This substance was reported to be essential for the optimal growth 

 of the fungoid coccus which uses citric acid in milk {Leuconostoc citrovorum 

 8081). The above workers suggested that a relationship exists between 

 folic acid and the natural agents active in the organism. Shive and co- 

 workers 671 succeeded in demonstrating the relationship of synthetic folic 

 acid to natural folinic acid. An active agent was prepared by formylation 

 of synthetic folic acid, followed by catalytic hydrogenation in the presence 

 of ascorbic acid. Williams 672,673 noted that choline oxidase activity was 

 significantly increased by LCF in rats fed aminopterin, while the stimulation 

 of activity caused by the addition of folic acid and ascorbic acid to choline 

 oxidase is inhibited by aminopterin added to the incubation mixture in 

 vitro. Williams postulated that LCF may itself be incorporated into an- 

 other molecule which is the specific coenzyme for choline oxidase. 



The relation of folic acid to choline utilization in the chick was investi- 

 gated by Dinning et al. 6U Livers of folic acid-deficient chicks had a decreased 

 ability to form methionine from homocystine or homocysteine in the pres- 

 ence of added choline or betaine. The addition of folic acid to replete chick 

 livers in vitro enhanced methionine synthesis, but the same condition could 

 not be produced in livers deficient in folic acid. Moreover, Verly and as- 

 sociates 675 reported that rats deficient in folic acid synthesized less choline 

 from C 14 -labeled methanol than did animals supplemented with folic acid 

 or LCF. 



The citrovorum factor occurs in dried brewer's yeast, largely in the 

 bound form. 676 It can be liberated from the bound form by a CF-liberating 

 factor; this appears to be identical with folic acid conjugase, which has 

 previously been described. The CF-liberating enzyme is activated by 

 ascorbic acid. 677 



669 C. A. Nichol and A. D. Welch, Proc. Soc. Exptl. Biol. Med., 74, 403-411 (1950). 

 fi7 ° H. E. Sauberlich and C. A. Baumann, J. Biol. Chem., 176, 165-173 (1948). 

 871 W. Shive, T. J. Bardos, T. J. Bond, and L. L. Rogers, J. Am. Chem. Soc, 72, 2817- 

 2818 (1950). 



672 J. N. Williams, Jr., J. Biol. Chem., 191, 123-127 (1951). 



673 J. N. Williams, Jr., J. Biol. Chem., 192, 81-85 (1951). 



674 J. S. Dinning, C. K. Keith, and P. L. Day, J. Biol. Chem., 189, 515-520 (1951). 



675 W. G. Verly, J. M. Kinney, and V. du Vigneaud, /. Biol Chem., 196, 19-23 (1952). 



676 C. H. Hill and M. L. Scott, J. Biol. Chem., 196, 189-193 (1952). 



677 C. H. Hill and M. L. Scott, /. Biol. Chem., 196, 195-199 (1952). 



