52 



David Shemin and Jonathan Wittenberg 



but their activity was also equal to that of the terminal 

 carbon atoms of the vinyl group (A9, B9) and the correspond- 

 ing carbon atoms of the propionic acid side chains (C9, D9). 

 The methyl-bearing carbon atoms in all the pyrrole rings 

 (A4, B4, C4, D4) had the same activity as the proximal 

 carbon atoms of the vinyl side chains of Rings A and B (A8, 

 B8) and their counterparts in the propionic acid side chains 

 of Rings C and D (C8, D8). Also the carbon atoms numbered 

 5 in the pyrrole rings had the same activity as all ring carbon 

 atoms to which the longer side chains are attached (A3, B3, 



Table IV 



i*C Activities of Fragments of Pyrrole Rings 

 (Shemin and Wittenberg, 1951) 



♦Addition of activities found for pyruvic and a-ketobutyric acids. 



C3, D3). This diagonal relationship can be seen from Fig. 4. 

 The carboxyl group of the a-ketobutyric acid samples which 

 corresponds to the carbon atoms numbered 2 contained no , 

 ^*C, which is in agreement with the previous finding that the 

 source of these carbon atoms is the a-carbon atom of glycine. 

 Similarly, in the experiment using carboxyl labelled acetate, 

 all carbon atoms numbered 5 and 3 had similar activities 

 (average values given in Fig. 4). The carboxyl group of the 

 porphyrin (ClO, DlO), found only in Rings C and D, is derived 



