IV. BIOCHEMICAL SYSTEMS 19 



general importance of GPC as an intermediary in the phospholipid metabo- 

 lism of mammals. 



Baccari^^ has compared the hydrolysis of phosphorylcholine and of glyc- 

 erophosphoric acid by phosphatases in pancreas, intestinal mucosa, and 

 brain. Phlorizin and fluoride inhibited both hydrolyses. Hydrolysis of the 

 glycerophosphate but not of phosphorylcholine was greatly accelerated by 

 magnesium chloride. 



The direct phosphorylation of choline by adenosine triphosphate in the 

 presence of extracts from brewer's yeast and preparations from liver, brain, 

 intestine, and kidney of several species has been reported by Wittenberg 

 and Kornberg.*^'^ The enzyme, choline phosphokinase, also catalyzed the 

 phosphorylation of aminoethanol and of the mono- and dimethyl (and 

 ethyl) aminoethanols. It was suggested that these phosphorylated deriva- 

 tives may be activated precursors of the respective phosphatides even 

 though previous attempts to demonstrate such a conclusion have been 

 unsuccessful. 



Reference has been made previously to the occurrence of sphingosylphos- 

 phorylcholine. It is oxidized more rapidly by minced liver, kidney, and 

 brain than by other tissues of the guinea pig.^® 



2. Choline and Transmethylation 



The first intimation that the dietary supply of choline might have nutri- 

 tional significance resulted from survival studies on depancreatized dogs 

 subsequent to the discovery of insulin by Banting and Best. Both Fisher^* 

 and Allan et al}^ observed fatty and severely degenerated livers in the 

 animals deprived of the pancreas but supplied with insulin. In the latter 

 study, survival was reported in the case of one animal that received raw 

 pancreas in its diet. Six years passed before it w^as reported that the pro- 

 tective action of raw pancreas in depancreatized dogs was duplicated by 

 the feeding of lecithin.^^-'^ At this time Best et al.^^ observed that fatty 

 livers resulted from feeding rats mixed grains and fat and that dietary 

 lecithin was lipotropic, i.e., it prevented the accumulation of hepatic fat 



32 V. Baccari, Boll. soc. ital. biol. sper. 20, 397, 398 (1945). 



sa-* J. Wittenberg and A. Romberg, J. Biol. Chem. 202, 430 (1953). 



3' M. Aloisi, Atti accad. nazl. Lincei, Rend. Classe sci. fis. mat. e nat. 2, 98 (1947). 



3" N. F. Fisher, A771. J. Physiol 67, 634 (1924). 



35 F. N. Allan, D. J. Bowie, J. J. R. Macleod, and W. L. Robinson, Brit. J. Exptl. 

 Pathol. 5, 75 (1924). 



36 J. M. Hershey, Am. J. Physiol. 93, 657 P (1930). 



" J. M. Hershey and S. Soskin, Am. J. Physiol. 98, 74 (1931). 



38 C. H. Best and J. M. Hershey, J. Physiol. (London) 75, 49 (1932). 



39 C. H. Best, J. M. Hershey, and M. E. Huntsman, J. Physiol. (London) 75, 56 

 (1932). 



