HANS KLENOW 



Discussion 



Chairman: C. H. Waddington 



J. Brachet. Is there anything known about the intracellular distribution of the various 

 enzymes involved in nucleotide synthesis? 



H. Klenow. The enzyme system responsible for the incorporation of adenine into 

 AMP in the presence of ribose-5-phosphate and ATP is present in the soluble part 

 of pigeon-liver homogenate. 



H. V. Bmndsted. Have you any indication that any of the B-vitamins enter into the 

 synthesis of RNA ? I am asking because we have shown that RNA accelerates re- 

 generation in starved planarians, and so does riboflavin. The constituents of RNA 

 given separately but in the right proportion act as a poison. 



H. Klenow. It is known from the work of Greenberg and of Buchanan that citrovorum 

 factor is significant for the formation of the purine part of inosinic acid. This acid 

 can apparently be formed from 4-amino-5-imidazole-carboxamide ribotide and 

 formic acid. This incorporation of formic acid, which appears in G( 2 > of the purine 

 ring, seems to require citrovorum factor as a coenzyme. 



78 



