X. EFFECTS OF DEFICIENCY 85 



ever, considered their data evidence for a role of B12 in the reactions which 

 result in the formation of serine from glycine, and Stekol et al. arrived at 

 the same conclusion. '^^' ^^* Choline prevented depletion of B12 in the livers 

 of rats, but not of mice, on choline-deficient diets containing sulfasuxidine 

 and iodinated casein. ^"^ The decrease in the epinephrine content of the 

 adrenals of rats on a low B12 diet containing desiccated thyroid or iodinated 

 casein was partially prevented by B12, and it was suggested that B12 may 

 function in the formation of the methyl group of epinephrine.-"^ The sar- 

 cosine oxidase content of livers of hyperthyroid rats deficient in folic acid 

 was unaffected but was reduced in Bi2-deficient animals.-"^ Bi2, however, 

 was ineffective in restoring the enzyme content. 



Williams et al}'"'^^' -"'^ compared the effect of a deficiency of B12 on liver 

 xanthine oxidase and betaine-homocysteine transmethylase levels and 

 concluded that the decreased xanthine oxidase activity was an indirect 

 metabolic effect, whereas the data indicated that the transmethylase may 

 require B 12 as a cof actor or as a precursor of a cof actor. Hawk and Elve- 

 jgj^207c found no evidence of a choline-sparing action of Bi2f , a biologically 

 different form of B12 recently described by Lewis et alr^'^^ Stekol et alP''^ 

 observed no effect of B12 deficiency on the transmethylation that jdelds 

 choline from methionine although the incorporation of methyl into choline 

 was diminished in both folic acid-deficient and pyridoxine-deficient animals. 

 It was suggested that B12 , folic acid, and pyridoxine may be more concerned 

 with the synthesis of methyl acceptors than with transmethylation itself. 



Dubnoff has made the interesting suggestion that one of the functions of 

 a B12 derivative is the reduction of homocystine to homocysteine, believed 

 to be the actual acceptor of methyl.^"* A B12 concentrate increased the sulf- 

 hydryl content of rat liver slices, and this effect was particularly noticeable 

 in experiments on Bi2-deficient rats. The activity was associated with the 

 B12 color after paper chromatography, although crystalline B12 and Bi2a were 

 negative. In subsequent observations Dubnoff demonstrated that homo- 

 cysteine or homocystine plus a reducing agent replaced Bi2 or methionine 



^os J. J. Travers and L. R. Cerecedo, Federation Proc. 11, 457 (1952). 



206 A. D'lorio and G. W. E. Plaut, Arch. Biochem. and Biophns. 41, 153 (1952). 



2"' M. E. Swendseid, A. L. Swanson, and F. H. Bethell, Arch. Biochem. and Biophys. 



41, 138 (1952). 

 2"" J. N. Williams, Jr., W. J. Monson, A. Sreenivasan, L. S. Dietrich, A. E. Harper, 



and C. A. Elvehjem, J. Biol. Chem. 202, 151 (1953). 

 ^O'b J. N. Williams, Jr., W. J. Monson, A. E. Harper, and C. A. Elvehjem, ./. Biol. 



Chem. 202, 607 (1953). 

 20^" E. A. Hawk and C. A. Elvehjem, J. Nutrition 49, 495 (1953). 

 ^o'd U. J. Lewis, D. V. Tappan, and C. A. Elvehjem, J. Biol. Chem. 194, 539 (1952); 



199, 517 (1952). 

 ^o^* J. A. Stekol, S. Weiss, P. Smith, and K. W. Weiss, ./. Biol. Chem. 201, 1 (1953). 

 20* J. W. Dubnoff, Arch. Biochem. 27, 466 (1950). 



