THE PROTEINS AND THEIR METABOLISM 



109 



The fate of valin in the body is not definite. Dakin (1913) has found 

 that it does not give rise to either glucose or acetone bodies. From a priori 

 yawmit^ and from experiences that were obtained with substances chem- 

 ically related to it, one would have expected the transformation into glu- 

 cose <>f three of its carbons. 



The fate of leucin is definitely known. It does not give rise to any 

 iihicose. but uives rise to largt) amounts of P-hydroxybutyric acid and 

 acetone. Baer and Blum, 1900 (a) ; Halscy, 1903; Dakin, 1913; Ringer, 

 Fiankel and Jonas, 1913 (a) ; Embden Salomon and Schmidt, 1906). The 

 fx-carb<n is probably the first to suffer oxidation and the molecule becomes 

 i-< diverted into iosovalerianic acid, which on demethylation is converted 

 into butyric acid, and which on p-oxidation is converted into P-hydroxy- 

 Imrvric acid, aceto-acctic acid and acetone. 



CH, CH 3 

 \/ 

 Clio 



I 



(J-CH 2 Deami- 

 nation 



a-CHXHo 



CH 3 



XX 



CH, 



Oxida- 

 tion 



CH 3 CH, 



V 



P-CH, 



o>CHOH 



CH, CH 3 



\S 



CH 2 



I 



P-CIL Oxida- a-CH 2 Demethyl- 

 tion | ation 



o-CO COOH 



COOH 

 Leucin 



COOH 



COOH 



C0 2 



Isovalerianic 

 acid 



('II ; CH 



CH 



CP 



CH 3 CH 3 CH 



I I I 



Oxidation CHOII Oxidation CO Decarboxvlation CO 



COOH 

 Cutvric acid 



CH 2 



I 

 COOH 



P-hydroxy 

 butvric acid 



COOH 



Aceto-acetic 

 acid 



CH. 



C0 2 



laoleucin and normal leucin. In Dakin's experiments (1913) we find 

 an increase of 3.8 and 2.9 grams of glucose after administering 15 

 irrams of isoleucin. Dakin is not inclined to consider that as conclusive 

 pruof that it is glucogenetic. From the structure of the normal leuein, 

 however, one may assume the possibility of sugar formation. Normal 

 valerianic acid may be formed after deamination and decarboxylatkm and 

 this has been shown to be glucogenetic to the extent of three of its carbons. 



