396 VIII. CHOLESTEROL AND RELATED STEROLS 



metabolite, pantoyltauryl-p-anisidide, was added to normal liver slices, 

 these workers-^- noted a reduction in steroid and lipid synthesis, presum- 

 ably due to the relatively low content of CoA. A partial reversal could be 

 brought about by pantethine, but not by pantothenic acid itself. Klein 

 and Lipmann263 ^jgQ pointed out that a parallehsm exists in living yeast be- 

 tween the CoA level and the capacity to synthesize ergosterol and total 

 lipid. Boyd^^^ subscribes to the hypothesis that the level of tissue choles- 

 terol depends upon the CoA content, and that the latter is obviously re- 

 quired in the synthesis of the sterol. 



In a more complete study of the mechanism of synthesis of cholesterol, 

 Rabinowitz and Gurini^^ found that l-C**-acetyl CoA was more efficient 

 in cholesterol synthesis than was l-C'^-acetate. 2-C^ ^-Pyruvate was also 

 a better source of cholesterol than was free acetate, presumably because the 

 former was more readily incorporated into the active acetyl CoA compound. 

 It was reported that, in addition to CoA, DPN, ATP, and AMP were hke- 

 wise required. '^^ 



(b) Biotin Deficiency. Curran'-®^ reported that, although the rate of 

 fatty acid synthesis was somewhat increased in biotin-deficient rats, that of 

 cholesterol remained normal. In fact, the increased rate of fatty acid syn- 

 thesis was related to the inanition rather than to the biotin deficiency itself. 

 On the other hand, Okey and her co-workers=^^^ observed that biotin-deficient 

 rats failed to store excess cholesterol ester in the liver when fed egg diets 

 high in cholesterol. When an avidin-rich diet containing cholesterol was 

 given, a marked decrease in liver cholesterol ester occurred, in spite of the 

 high cholesterol intake. The role of biotin in cholesterol synthesis thus 

 seems questionable. 



(c) Deficiencies in Miscellaneous Vitamins. The role of the other B vita- 

 mins in cholesterogenesis is not clear. Riboflavin is apparently without 

 activity, -^^ while pyridoxine would seem to have only a limited effect. 

 Guggenheim and Olson^^^ found that total cholesterol synthesis in rats was 

 not appreciably reduced in nutritional disorders such as deficiencies in 

 thiamine, pantothenic acid, biotin, and choline; the decreased production 

 did not vary much from that of pair-fed controls. However, the specific 

 activity of the adrenal cholesterol was found to be decreased in all types 

 of deficiency, as well as in the pair-fed controls. Lecoq et al.^^^ suggested 



2" H. P. Klein and F. Lipmann, J. Biol. Chem., 203, 95-99 (1953). 

 2" G. S. Boyd, Biochem. J., 55, 892-895 (195.3). 

 265 G. L. Curran, Proc. Soc. Exptl. Biol. Med., 75, 496-498 (1950). 

 2«5 R. Okey, R. Pencharz, S. Lepkovsky, and E. R. Vernon, /. Nxdrition, U, 83-99 

 (1951). 



2" K. Guggenheim and R. E. Olson, /. Nutrition, 48, 345-358 (1952). 



268 R. Lecoq, P. Chauchard, and H. Mazoue, Bull. soc. chim. bioL, 30, 298-305 (1948). 



