TRIGLYCERIDES AND FATTY ACIDS 165 



can prevent the fat from being oxidized. The review by MacKay^"'' on 

 the subject supports this theoretical mechanism for the a(;tion of carbo- 

 hydrate. 



(h) Experimental Evidence Concerning the Mechanism of the Action of 

 Carbohydrate on Ketonuria. a'. In Vitro Analogy of Coupled Reactions: 

 The most cogent arguments for the ketolysis theory are in in vitro experi- 

 ments of Shaffer.^ 1^ In these tests, it was noted that only a slight oxidation 

 of an alkaline solution of acetoacetate occurred in the test-tube when H2O2 

 was added, unless glucose was also present. Thus, only 8% of acetoacetate 

 disappeared in sixteen hours when H2O2 was used alone, while, in the 

 presence of a small amount of glucose, 74% of the ketogenic material was 

 oxidized. It was found that, as a requirement for this reaction, glucose 

 itself must be oxidized.^^^ According to the latter workers, "the rate of 

 acetoacetate disappearance becomes equal to and parallels the rate of sugar 

 oxidatio7i; that is to say, the rate of keto acid consumption, or 'ketolysis,' is 

 determined and limited by the rate of sugar oxidation." Shaffer and Friede- 

 mann^i^ reported that glycolaldehyde, H0CH2-CH0, as well as glucose, 

 produced a ketolytic effect; some evidence was adduced that a condensation 

 product resulting from a Knoevenagel type of reaction had been formed 

 between this compound and one or two acetoacetate molecules, whereby 

 oxidation was accelerated. 



Further support for the theory that a coupled reaction occurs is to be 

 found in the experiments of West.^^"'^^^ Thus, a number of condensation 

 products, in which the addition was on the cc-carbon of the keto acid, were 

 found to be much more labile than the parent substances. These con- 

 densation products were shown to have higher reducing potentials than 

 that of acetoacetate, which would indicate a possible explanation for this 

 phenomenon on an electronic basis.^^^ West^^'' later proved that a con- 

 densation product was formed between acetoacetic ester and glucose. 

 It is stated that "it is plausible to suppose that various oxidations may 

 occur in the animal body in which one compound aids the oxidation of 

 another by combination with it, forming a complex more easily oxidized 

 by the body than one or both constituents y 



Another type of evidence which lends support to the theory that coupled 

 reactions can occur in the body is one described by Westerfeld, Stotz, 

 and Berg.^^^ These workers established the fact that the administration 

 of pyruvate accelerates the rate of alcohol metabolism. It was suggested 



"5 P. A. Shaffer and T. E. Friedemann, /. Biol. Chem., 61, 585-623 (1924). 



"6 E. S. West, /. Biol. Chem., 66, 63-75 (1925). 



*" E. S. West, /. Biol. Chem., 7^, 561-589 (1927). 



6>« W. W. Westerfeld, E. Stotz, and R. L. Berg, /. Biol. Chem., 1U> 657-665 (1942). 



