LIPID STORAGE UNDER ABNORMAL CONDITIONS 655 



taining homocysteine in the reduced state; they exclude the concept that 

 vitamin J$ u functions as a coenzyme in transmethylation in the organism. 



Vitamin Bi 2 , together with folacin, also improves the efficiency of betaine, 

 Z)L-methionine, dimethylaminoethanol and methylaminoethanol as dietary 

 replacements for choline in the rat. 679 The chick was able to utilize methyl 

 aminoethanol plus betaine HC1 or DL-methionine for growth or for the pre- 

 vention of perosis only when vitamin B ]2 was present. 689 Moreover, 

 dimethylaminoethanol could not serve as a replacement for choline in 

 growth, or to prevent perosis, unless the diet contained vitamin Bi 2 . 689 



In the later tests of Jukes and Stokstad 690 with chickens, it was found that 

 the addition of homocystine to a vitamin Bi2-free, choline-free diet actually 

 depressed growth. However, the growth response of the birds was mark- 

 edly improved by vitamin B 12 . Although the administration of choline or 

 betaine without vitamin B i2 resulted in an improvement in the condition of 

 the chicks, the response was no greater than the effects of the supplements 

 individually. However, when vitamin B 12 was also given, the growth 

 stimulus was further increased over that on the diet free from the vitamin. 

 Choline apparently acts as a methylating agent for homocystine on a diet 

 deficient in methionine only when vitamin Bi 2 is included in the ration. 



(d') "Labile Methyl" Groups and Choline Synthesis : The possibility that 

 other than preformed methyl groups may serve as sources of such groups in 

 the choline molecule has been demonstrated. It was reported that, on 

 oxidation of acetone, acetate 691 and formate 692 were formed. Formate is 

 known to contribute to the serine molecule. 693 



A number of workers, including Sakami, 692 du Vigneaud et a/., 694,695 and 

 others, 696 - 697 demonstrated that formate is converted to labile methyl. This 

 labile methyl has been detected in newly formed choline and methionine. 692 

 Sakami and Welch 696 reported that the conversion of formate to methyl 

 groups could be detected not only in the intact rat but also in rat liver slices. 

 It is suggested that folic acid is concerned with the metabolism of the one- 

 carbon compounds. Ressler and co-workers 697 noted that a quantitative 



689 A. E. Schaefer, W. D. Salmon, and D. R. Strength, J. Nutrition, M, 305-311 (1951). 



690 T. H. Jukes and E. L. R. Stokstad, J. Nutrition, 48, 209-229 (1952). 



691 E. Borek and D. Rittenberg, J. Biol. Chem., 179, 843-845 (1949). 



692 W. Sakami, J. Biol. Chem., 187, 369-378 (1950). 



693 W. Sakami, J. Biol. Chem., 176, 995-996 (1948). 



694 V. du Vigneaud, W. G. Verly, and J. E. Wilson, J. Am. Chem. Soc., 72, 2819-2820 

 (1950). 



695 V. du Vigneaud, W. G. Verlv, J. E. Wilson, J. R. Rachele, C. Ressler, and J. M. 

 Kinnev, J. Am. Chem. Soc., 78, 2782-2785(1951). 



696 W. Sakami and A. D. Welch, J. Biol. Chem., 187, 379-384 (1950). 



697 C. Ressler, J. R. Rachele, and V. du Vigneaud, J. Biol. Chem., 197, 1-5 (1952). 



