VOL. 4 (1950) PURINES AND PYRIMIDINES IN RIBOSIDIC LINKAGE 237 



study of enzymatic step reactions in vitro and the study with isotope labelled precursors in 

 vivo are equally indispensable and exert a mutual and valuable influence on each other. 

 An example is the importance of the Embden-Meyerhof glycolysis scheme for the 

 interpretation of the distribution of labelled carbon in glycogen from rats fed with 

 labelled carbon dioxide. The ingenious analysis by Wood and coworkers in this field 

 may well serve as an encouragement for investigators working in allied fields. 



SU?kLMARY 



The mechanism of incorporation of purines and pyrimidines into ribosidic Unkage has been 

 discussed from various points of view. Results gained from enzymatic studies are not in direct 

 agreement with observations made in intact organism using isotopes. Various ways of interpretations 

 are discussed. 



r£su!^i£ 



Le mecanisme de I'incorporation de purines et de pyrimidines dans la liaison ribosidique a 

 ete discute de differents points de vue. Les resultats obtenus par des etudes enzymatiques ne con- 

 cordent pas entierement avec les observations faites dans I'organisme intact au moyen d'isotopes. 

 Difierentes possibilites d'interpretation ont ete envisagees. 



ZUSAMMENFASSUNG 



Der Mechanismus der Einverleibung von Purinen und Pyrimidinen in die Ribosid-Bindung 

 ist von verschiedenen Gesichtspunkten aus erortert worden. Die aus enzymatischen Untersuchungen 

 gewonnenen Ergebnisse stimmen nicht voUig iiberein mit Beobachtungen welche im unversehrten 

 Organismus mittels Isotopen gemacht wurden. Verschiedene Erklarungsmoglichkeiten werden 

 besprochen. 



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Received April i6th, 1949 



