22 



S. S. COHEN 



for the synthesis of a viral unit, even though a famiHar pathway is known to 

 operate for the same substrate in the normal cell? 



Despite the evident interest of these problems of intermediary metabohsm 

 to the development of biochemical virology, it is not my intention to pursue 

 these questions further, at least not in the form of providing a biochemical 

 map separate from the consideration of biological and chemical problems of 

 polymer synthesis. Such maps and discussions of particular paths may be 

 found in a number of biochemical texts and in the innumerable reviews of 

 advances in these areas. 



HjOjPOCHj,0. 



OH OH 

 CYTIDYLIC ACID 



BACTERIAL NUCLEIC ACID 



RNA + DNA 



I 

 NHj 



DEOXYCYTIDYLIC 

 ACID 



HjOjPOCH 



H APOCHj^O I 



HC— CH 

 OH H 



CHjOH 



VIRUS NUCLEIC ACID 



H 



OH 



H.C 



H 



5-HYDROXYMETHYLDEOXYCYTIDYLIC ACID 



Fig. 1. The production of a virus-specific intermediary metabolite, 5-hydroxymethyl 

 deoxycytidylic acid (Flaks and Cohen, 1957). 



2. Viral Enzymes 



In recent years some viruses have been shown to have some intrinsic 

 catalytic activity, which may be termed enzymatic, as indicated by the 

 recent studies of the specific hydrolases of influenza virus and the T-even 

 bacteriophages. In the latter instance, the tail of the virus contams an enzyme 

 which can bore holes in bacterial ceU walls (Brown and Kozloff, 1957) and 

 liberate fragments contaming amino acids (Koch and Weidel, 195G). This 

 activity is apparently important in permittmg the penetration of viral DNA 

 into the bacterium. Although the substrates and reaction products of this 



