268 VI. ACETIC, FORMIC, AND PROPIONIC ACIDS 



acetate include glycogen, fatty acids, dicarboxylic acids, cholesterol, 

 protoporphyrin, and uric acid. The demonstration of the synthesis of 

 these compounds from acetate has been made possible by the use of labeled 

 acetic acid. Further information as to the mechanism of sjaithesis can be 

 gleaned by determining the particular carbon atoms involved, by degrada- 

 tion of the newly synthesized compounds by certain prescribed methods. 

 Thus, by various chemical and microbiological technics (Lactobacillus 

 casei, lactic acid bacillus from milk and cheese) , the isotope concentrations 

 of the several carbons in the glucose molecule have been determined. ^"^'^"^ 

 The portion of the cholesterol molecule affected in the synthetic reaction 

 has been ascertained by degradation of the sterols into the nucleus and 

 side chain. ^"^ 



a. Glycogen Synthesis. In discussing the precursors of any substance, 

 according to Bloch,i one must differentiate between (1) those which afford 

 a net increase in the quantity of the product, viz., reactions in which the 

 quantity of the precursor is the limiting factor, and (2) reactions in which 

 substances become totally or partly incorporated into a product without 

 affecting the rate of formation. 



(a) The Effect on Total Glycogen. According to the classical concept, 

 a glycogenic substance is one which increases glycogen deposition in fasted 

 animals, which causes the excretion of "extra sugar" in diabetic animals, 

 or which reduces ketonuria. When measured by any of these yardsticks, 

 acetic acid caimot be classed as a glycogenic compomid. Thus, neither 

 Ringer and Lusk^^" nor Deuel and Milhorat"^ could demonstrate any 

 increased D:N ratio in phlorhizinized dogs after the administration of 

 fairly large doses of sodium acetate. Although Geelmuyden"- did report 

 an increased D : N ratio which he interpreted as indicative of glucose for- 

 mation, the D:N ratio of the dogs in the control period was high, and 

 it is impossible to determine from his data whether or not glucose was 

 being formed. 



Although sodium acetoacetate, as well as the saturated even-carbon 

 acids from d to Cu, and also oleic acid, are not glycogen formers, '^ tri- 

 acetin was found to serve as a source of liver glycogen. *^^ However, all 



i»7 H. G. Wood, N. Lifson, and V. Lorhei, /. Biol. Chem., 159, 475-489 (1945). 

 108 De W. Stetten, Jr., and M. R. Stetten, J. Biol. Chem., 165, 147-155 (1946). 

 'o« K. Bloch and D. Rittenberg, ./. Biol. Chem., 145, 625-636 (1942). 

 "0 A. J. Ringer and G. Lusk, Z. phijsiol. Chem., 66, 106-119 (1910). 

 1" H. J. Deuel, Jr., and A. T. Milhorat, ./. Biol. Chem., 78, 299-309 (1928). 

 "2 H. C. Geelmuyden, Skand. Arch. Physiol., 40, 211-225 (1920). 

 113 H. J. Deuel, jr., J. S. Butts, H. Blunden, C. H. Cutler, and L. Knott, J. Biol. 

 Chem., 117, 119-129(1937). 



