LIPID STORAGE UNDER ABNORMAL CONDITIONS 657 



Bennett 701 interprets her findings as supporting the theory that a bacterial 

 synthesis of unknown factors influencing homocystine utilization obtains. 

 The ability of rats to grow on a homocystine-containing diet devoid of other 

 sulfur-containing amino acids and other known methyl donors has been 

 observed in a number of strains of rats. According to Bennett and 

 Toennies, 702 this capacity depends upon preexperimental nutritional condi- 

 tions. When the rats are prefed on sulfonamide, the intestinal flora are so 

 modified that methionine, but not homocystine, can be used. If choline or 

 certain liver fractions are fed to such animals, homocystine can be utilized. 

 It is obvious that bacteria, under certain conditions, may play a role in the 

 utilization of homocystine. However, du Vigneaud and co-workers 703 

 demonstrated that the degree of synthesis of the methyl group in choline 

 and creatine was comparable in bacteria-free rats and in control multicon- 

 taminated animals. 



Kelley et al. 70i have demonstrated the lipotropic effect of folic acid. 

 They explain this action as related to stimulation of the conversion of 

 glycine to serine, which has previously been demonstrated. 705 In this 

 manner, the drain on labile methyl groups is reduced, and more are available 

 for choline synthesis. 



(e') The Intracellular Distribution of Choline Oxidase : Further evidence 

 for the interrelationship of LCF, folic acid, and vitamin Bi 2 with choline 

 oxidase can be inferred from their similar distribution in the cell. Wil- 

 liams, 706 using Schneider's method of differential centrifugation for the 

 separation of the cell particles, 707 proved that choline oxidase was highly 

 concentrated in the mitochondria, while only small amounts were present 

 in the nuclei and microsome fractions. All of the vitamin fractions and 

 choline oxidase are more frequently localized in the mitochondria than in 

 other portions of the particulate matter; Williams believes that this indi- 

 cates their close relationship to each other. 



h'. Modification of the Lipotropic Action of Choline in the Presence of 

 Methyl Acceptors : The synthesis of choline by the methylation of ethanol- 

 amine is merely one of a series of methylations which can occur in the 

 animal body. Thus, Stetten and Grail 559 demonstrated that guanidoacetic 



701 M. A. Bennett, /. Biol. Chem., 163, 247-250 (1946). 



702 M. A. Bennett and G. Toennies, J. Biol. Chem., 163, 235-245 (1946). 



703 V. du Vigneaud, C. Ressler, J. R. Rachele, J. A. Reyniers, and T. D. Luckey, J. 

 Nutrition, 45, 361-376 (1951). 



704 B. Kelley, J. R. Totter, and P. L. Day, /. Biol. Chem., 187, 529-535 (1950). 



705 J. R. Totter, B. Kelley, P. L. Day, and R. R. Edwards, J. Biol. Chem., 186, 145-151 

 (1950). 



706 J. N. Williams, Jr., J. Biol. Chem., 194, 139-142 (1952). 



707 W. C. Schneider, ./. Biol. Chem., 176, 259-266 (1948). 



