II. CHEMISTRY 157 



Massengale et al}-^ demonstrated that the yeast Saccharomyces cerevisiae 

 elaborated widely different amounts of ergosterol, according to the sugar 

 which supplied the carbon to the basal medium. This work contributes one 

 of the few bits of information available on the mechanism of sterol forma- 

 tion. Seven fermentable sugars were used, with the finding that di- and 

 trihexoses occasioned the synthesis of greater amounts of ergosterol than 

 did the monohexoses (singly or in admixture) into which they are hydro- 

 lyzed. The amounts of ergosterol produced bore no relation to the protein 

 or fat content of the yeast cells. It is a reasonable inference, therefore, 

 that the monohexoses which are split from the higher sugars by the yeast 

 enzymes exist at the instant of cleavage in forms particularly suitable for 

 synthesis into sterol. According to this concept, ergosterol is primarily a 

 product of carbohydrate metabolism. 



In this connection, an experiment by Maclean and Hoffert^^" is significant. 

 It was found that the presence of sulfite in the sugar solution in which the 

 yeast was incubated resulted in a marked decrease in ergosterol production 

 but in little or no interference with the elaboration of fatty acid. The 

 argument was advanced that in the formation of sterol, but not of fatty 

 acid, an aldehyde removable by sulfite comes into the picture between the 

 hexose and the final product. The action of the sulfite might have been 

 better explained as that of an oxygen remover. Actually, the production 

 of ergosterol is enhanced by the presence of oxygen carriers such as methy- 

 lene blue and various inorganic per-salts.^^^ 



Halden and his associates, ^^^ who maintain that there is a biogenetic 

 relationship between fats and sterols, have succeeded in increasing the 

 ergosterol production of yeast ten- to fortyfold by keeping it in a state of 

 semidehydration and supplying alcohol and air. Under these conditions the 

 normal processes of budding and fermenting are repressed, while the pro- 

 duction of fat and sterol, especially the latter, is augmented to an extraor- 

 dinary degree. Halden 's papers contain a valuable review of ergosterol 

 production in yeast. 



In the higher plants even less is known about the origin of the ubiquitous 

 ergosterol. Heilbron and Sexton^^^ suggested that it arises from the simul- 

 taneous oxidation and reduction (dehydrogenation and hydrogenation) of 

 sitosterol, which at the time (1929) was believed to have 27 carbon atoms, 

 the same as ergosterol. This would relate the known wide occurrence of 



1" O. N. Massengale, C. E. Bills, and P. S. Prickett, J. Biol. Chem. 94, 213 (1931). 



"» I. Smedley Maclean and D. Hoffert, Biochem. J. 20, 343 (1926). 



"1 W. G. Bennett, U. S. Pat. 2,059,980 (1936). 



"2 W. Halden, Hoppe-Seyler's Z. -phxjsiol. Chem. 225, 249 (1934) ; Austrian Pat. 140,190 



(1934); M. Sobotka, W. Halden, and F. Bilger, Hoppe-Seyler's Z. physiol. Chem. 



234, 1 (1935). 

 1" I. M. Heilbron and W. A. Sexton, Nature 123, 567 (1929). 



