44 CHOLINE 



bon may be completely oxidized or built into serine or any other formate- 

 accepting anabolic product depending on a diversity of metabolic factors. 

 The demonstration of the loss of labile methyl groups by oxidation makes 

 understandable the continuous need of the organism for replacement meth- 

 yls. 



7. Other Aspects of Methyl Transfer and Oxidation 



Dimethylsulfone has been isolated from beef blood^^^ and adrenal cortex-'^ 

 and from the plants Equisetum palustre, E. arvcnue, and E. hyemale.™ • -^^ 

 Inasmuch as so little is known about the intermediate steps in the oxida- 

 tion of sulfur, it cannot be said that this compound is not a normal inter- 

 mediate. However, it appears most unlikely that it is important in trans- 

 methylation. Smythe demonstrated the formation of hydrogen sulfide from 

 cysteine by liver slices and suggested that it might be a precursor of the 

 sulfone.^^^ 



The chemical mobility of one methyl group in betaine, at least, was ob- 

 served by Willstatter at the beginning of the century.-" If heated to 300° 

 it is converted in part to the methyl ester of dimethylaminoacetic acid. 

 Challenger et al. extended this observation to include the transfer of methyl 

 from betaine under the influence of heat with the formation of dimethyl 

 derivatives of selenium, tellurium, and sulfur from selenite, tellurite, and 

 sulfite, respectively .^^^ • -" It was also demonstrated that the heating of 

 betaine with aromatic primary amines such as aniline, p-toluidine, or 

 iS-naphthylamine resulted in a transfer of methyl and the formation of the 

 corresponding monomethyl derivatives. Dimethylthetin also yielded the 

 methyl ester of thiomethjdacetic acid on heating.-^^ 



Methylation of selenides and tellurides in the animal organism has been 

 the subject of much controversy since the original report by Hofmeister in 

 1894.22* ^Y^Q excretion in expired air of a volatile selenide or telluride has 

 not been questioned, but proof that the substance in question was a methyl 

 derivative has been unsatisfactory. However, McConnell and Portman have 



215 J. J. Pfiffner and H. B. North, J. Biol. Chem. 134, 781 (1940). 



216 L. Ruzicka, M. W. Goldberg, and H. Meister, Helv. Chim. Acta 23, 559 (1940). 

 2" P. Karrer and C. H. Eugster, Helv. Chim. Acta 32, 957 (1949). 



218 P. Karrer, C. H. Eugster, and D. K. Patel, Helv. Chim. Acta 32, 2397 (1949). 



219 C. V. Smythe, J. Biol. Chem.. 142, 387 (1942). 



220 R. Willstatter, Ber. 35, 584 (1902). 



221 F. Challenger and C. Higginbottom, Biochcm. J. 29, 1757 (1935). 



222 F. Challenger, P. Taylor, and B. Taylor, /. Chem. Soc. 1942. 48. 



223 F. Challenger and P. Fothergill, Biochem. J. 45, x.xvii (1949). 



224 F. Hofmeister, Arch, exptl. Pathol. Pharmakol. 33, 198 (1894). 



