348 



INOSITOLS 



.4. suboxydans 



are those oriented at approximately right angles to the thick plane of car- 

 bon atoms in the "chair" conformation of the cyclohexane ring. Equatorial 

 hydroxyl groups, i.e., those extending the thick plane formed by the carbon 

 atoms, are not oxidized by this organism. Franzl and Chargaff^"' ^^ have 

 obtained cell-free enzyme preparations from A. suhoxydans which oxidize 

 m?/o-inositol and other inositols in the same manner as do the whole cells. 

 The enzyme is present in particulate material which is sedimented by 

 20,000^' for 2 hours but which remains in the supernatant fluid after 

 centrifugation at 2000^ for 30 minutes. A heat-stable cofactor, obtained 

 from whole cells, accelerates the oxidation of m(/o-inositol by the enzyme 

 but is not required for the oxidation of glucose. This factor may be replaced 

 in part by Ca++ or Mg++. The cell-free preparations did not oxidize sorbitol, 

 which would seem to indicate that separate enzymes are involved in the 

 oxidation of polyhydric alcohols and cyclitols, respectively, by this 

 organism. 



Aerobacter aerogenes may be grown under aerobic conditions with myo- 

 inositol as the sole source of carbon. Magasanik'^^ has obtained consider- 

 able information about the pathway of inositol degradation by this 

 organism. Cells grown on m?/o-inositol under aerobic conditions fermented 

 m?/o-inositol to yield 0.68 mole of CO2, 0.72 mole of ethanol, and 1.54 

 equivalents of an unknown acid. Experiments with inhibitors led to the 

 conclusion that glucose was not an intermediate. 2-Keto-m?/o-inosito] and 

 L-l,2-diketo-m?/o-inositol were fermented by these cells two to three times 

 more rapidly than m?/o-inositol. L-l-Keto-m?/o-inositol was also fermented, 

 but no more rapidly than w?/o-inositol. The following metabolic pathway 

 was proposed by Magasanik. 



7nyo-Inositol 



2-Keto-?« 7/0- inositol 



L-l,2-diketo-??i^o-inositol ; 



HO O 



I II 

 H3C-C-C-O- -<- 



H 

 OH 



H3C-C-OH -<— 

 t 

 H 



O O 



H3C-C-C-O 



o 



II 

 H3C-C-0- 



C02 



