IV. BIOCHEMICAL SYSTEMS 347 



Phytin occurs also in animal tissues, for example, in the nucleated eryth- 

 rocytes of the chicken and turtle. ^^ 



3. Lipotropic Effect of Inositol 



There are a number of dietary variables which can lead to deposition of 

 unusually large amounts of lipid in the liver. Certain nutrients favor this 

 deposition, whereas others (lipotropic agents®") favor mobilization of the 

 lipids and a return to the normal fat content of the liver. Choline®" and 

 other biological methyl donors are particularly well known as dietary 

 lipotropic agents, but inositol is also effective under certain conditions in 

 both experimental animals®^"®^ and human subjects.®^' ®^ The effect of 

 inositol is apparent even with diets containing an adequate supply of 

 methyl group donors.®-- ®® Although relatively little is known concerning 

 the mode of action of lipotropic agents, at least two of them — choline and 

 inositol— are essential constituents of phospholipids, and it seems likely 

 that their effectiveness in reducing liver fat may be a reflection of that 

 fact. Since all other vitamins eventually become structural units of proto- 

 plasm too, it seems arbitrary to separate the lipotropic activities of choline 

 and inositol from their respective "vitamin" activities.®® 



B. METABOLISM OF INOSITOL 

 1. In Bacteria 



Although the pathways of inositol metabolism in bacteria are better 

 understood than those in animal tissues, knowledge in this field is still in a 

 relatively primitive state. 



The oxidation of 7n?/o-inositol®^ to yield m?/o-inosose-2®^ can serve as the 

 major source of energy for the growth of Acetobacter suboxydans. The oxida- 

 tion system is not specific for m^/o-inositol ; other polyhydric cyclohexanes 

 having polar hydroxy! groups are also attacked.®^ Polar hydroxyl groups 



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